Let's debate on gas regular or premium which is the best?

[Poirot1959]

I have been reading a lot on the use of regular vs premium gas. 87 to 93. Now it's my understanding that the higher the octane the better bang for your buck. Thus increasing the mileage and also doing some kind of cleaning as all corporation are advertising.

 

On my past experience, I always notice an increase in mileage when I use a higher octane gas. But I hve been reading here that in some case it might damage your engine.

 

Now don't get me wrong, but why should a higher octane gas damage your engine? And beside the obvious ping problem when you have a very high compression ratio and you use regular, why would the contrary be bad.

 

Here is what Shell Canada is saying about

 

Shell V-Power is our best, most advanced gasoline that contains the highest concentration of the NEW Nitrogen Enriched Cleaning System, a unique and patented formula exclusive to Shell. With five times the amount of cleaning agents required by government standards, Shell V-Power gasoline cleans up engine gunk faster than Shell Nitrogen Enriched Bronze gasoline and is designed for all vehicles – even today's most complex and advanced vehicles

 

And this is just one example as all other are saying close to the same thing

[akirby]

I have been reading a lot on the use of regular vs premium gas. 87 to 93. Now it's my understanding that the higher the octane the better bang for your buck. Thus increasing the mileage and also doing some kind of cleaning as all corporation are advertising.

 

On my past experience, I always notice an increase in mileage when I use a higher octane gas. But I hve been reading here that in some case it might damage your engine.

 

Now don't get me wrong, but why should a higher octane gas damage your engine? And beside the obvious ping problem when you have a very high compression ratio and you use regular, why would the contrary be bad.

 

Here is what Shell Canada is saying about

 

Shell V-Power is our best, most advanced gasoline that contains the highest concentration of the NEW Nitrogen Enriched Cleaning System, a unique and patented formula exclusive to Shell. With five times the amount of cleaning agents required by government standards, Shell V-Power gasoline cleans up engine gunk faster than Shell Nitrogen Enriched Bronze gasoline and is designed for all vehicles – even today's most complex and advanced vehicles

 

And this is just one example as all other are saying close to the same thing

 

It's relatively simple but often gets confused.

 

Higher octane simply allows you to run higher compression and/or more advanced timing without causing knock. Higher compression and more timing yields better performance and better mpg.

 

Compression is usually fixed based on the engine heads and pistons and stroke. Timing can be changed by the PCM. If an engine is designed for 87 octane and is not designed to advance the timing to take advantage of 91 or 93 octane then using premium is simply a waste of money and won't do anything.

 

However, if the PCM is designed to advance the timing as much as possible then you can get better performance with premium fuel. This is easy to spot because the mfr will either recommend premium fuel or explicitly tell you that using premium will yield better performance. If the OM doesn't say anything about premium fuel then it's probably not going to help.

 

The other issue USED to be a big difference and that is Premium fuel used to have far more detergents than regular fuel (Amoco Premium or "white" gas was one of those back in the 60s/70s). But in that case it was just the added detergents that made the difference not the octane. That seems to be what Shell is doing now with V-Power but honestly I think even the most basic regular fuel today has plenty of detergents so whatever they're offering is overkill and just marketing. Even if it wasn't you'd only have to use it every once in a while.

 

Whether it's worth it is up to you but I'd use the cheapest 91 octane fuel I could find and I wouldn't worry about Shell V-power per se.

[BlackBetty]

Your cars computer is tuned for regular so use regular.

 

Shell want to sell more gas. Whether your car requires it or not they make more money when you buy more expensive fuel.

 

Just buy the correct fuel for your car and leave it at that. I'd listen to Ford over Shell about what's better for your car.

Edited November 15, 2012 by BlackBetty

[2011se25]

In theory "If your car calls for regular, you waste your money buying premium". For conventional petrol, premium doesn't contain more energy per litre, instead it's less likely to cause premature detonation, meaning it is useful in higher compression engines where premature detonation can happen. These high compression engines are high performance engines that will call for premium.

 

Now, a lot of areas add up to 10% ethanol to their gasoline, and ethanol has a lower energy content than gasoline. However in many cases the premium (91 octane) fuel sold in these markets are 100% dinosaur-bones. This results in improved fuel economy, however it's very much "YMMV" to determine if it's worth the cost. Also midgrade (89) is half 87, half 91, so you will have 5% ethanol. However there's other problems caused by added ethanol. It can cause increased fouling, moisture, and other problems in your fuel system. In fact in small engines (lawn mower, snow mobile, etc) it's preferable to use premium to avoid ethanol because these engines are particularly susceptible to problems. Ethanol in any quantity in fuel is a scam.

 

On your quote from Shell, the gas station may use a different additive/ detergent package in premium. Is it better? Is it just marketing babble? Hard to tell. But in my province ALL gasoline comes from one refinery, and the only difference is the additive package. I haven't noticed any differences brand to brand in my Fusion, but a coworker with a Buick Enclave has (known) problems with fouled injectors. Supposedly there's more problems with using cheap gas with a poor additive package. My coworker pointed out that at Top Tier gas http://www.toptiergas.com/retailers.html few Canadian retailers are certified.

 

I ran a tank of premium through my Fusion as a test and noticed no change in economy. YMMV and feel free to experiment. I recommend being as scientific as possible. I noticed no difference, yet I have colleagues that swear they get better economy, and the car doesn't downshift as much (doing a long commute on the same highway every day).

[FusionDiffusion]

I use premium because around here all the other grades have ethanol. I get better milage (enough to justify the higher cost), but I haven't been able to determine how much of it is due to ethanol and how much of it is due to timing advance, but I suspect most of it is due to the ethanol (no ethanol-free 87 octane in my area to compare with).

 

Allen's explanation of the timing advance available in some PCM designs is true, but where I disagree is over the fact of whether it would be listed in the owner's manual. Some cars advance timing automatically but they still list 87 octane as recommended in the manual. This mostly has to do with getting better results in the EPA milage tests without making it seem like the customer has to use more expensive gas. It's hard to know this for sure unless you do your own scientific testing or get ahold of a Ford powertrain engineer.

 

Shell's claims about cleaning your engine better with V-power has nothing to do with the octane of the fuel. It's just the additive package. They put more in their premium gas to "up-sell" it more, which helps promote the false notion that premium is always "better" for your particular vehicle.

 

This doesn't apply to the OP, but those of you that have EcoBoost engines will see a benefit with premium gas as a result of the turbocharging. The engines were designed to run on 87 octane without problems, but you get more HP and torque with premium (the power ratings were done with premium gas and there's usually an asterisk denoting this).

[BlackBetty]

Check this out:

 

 

[Poirot1959]

Wow thanks all of you wh did clarify this information.

 

I am getting a Titanium so I will definitly use premium gas as this is the one recommended by Ford. But it's amazing at what corporation will do to get you to spend more money.

 

Also if Ethanol is some kind of bad with our engine, why would they keep using it or selling it.

 

Again thanks for you info.

[tsetse51]

................if Ethanol is some kind of bad with our engine, why would they keep using it or selling it.

 

Ethanol in gasoline is made primarily from corn. The lobby for agricultural producers is strong, and promotes the use of ethanol because it makes them mountains of money. Thus, food prices are driven up, and fuel has less energy content. All to feed the greed of corn produces.

[Poirot1959]

Ethanol in gasoline is made primarily from corn. The lobby for agricultural producers is strong, and promotes the use of ethanol because it makes them mountains of money. Thus, food prices are driven up, and fuel has less energy content. All to feed the greed of corn produces.

 

Unbeliveable how much corn is in our life. It's in almost everything we eat (process food anyway), pills, and more.

 

I guess I better be more carefull when I eat popcorn now, :P

[akirby]

I don't believe Ford recommends premium on the Titanium 2.0L EB. It's optional.

[2011se25]

Check this out:

 

Interesting test. Important to note is Europe uses a different method of calculating octane (RON) vs. America/Canada which uses AKI. That results in the RON value being 4-5 higher than the AKI number. Though I believe standard regular in Europe is RON 95, equivalent to AKI 90-91. Also interesting is this was done in a GTI, which is a performance car, and they measured power and not fuel economy.

 

Also if Ethanol is some kind of bad with our engine, why would they keep using it or selling it.

 

Definitely agriculture lobby, subsidies, etc. Also why HFCS is used so frequently instead of cane / beet sugar, even though there's evidence that it isn't healthy. Ethanol has the perception of being "green" / "renewable", but more diesel is burned in it's production (tractors, trucks), and petroleum based fertilizers used than energy is captured in the fuel. As well MTBE is / was used as an octane booster / oxygenate additive (promotes cleaner burning, lower smog emissions) post-leaded fuel, and MTBE is a carcinogen, and made its way into ground water. Ethanol is an alternative, again promoted by agriculture lobby. Other alternatives exist.

[BlackBetty]

 

Interesting test. Important to note is Europe uses a different method of calculating octane (RON) vs. America/Canada which uses AKI. That results in the RON value being 4-5 higher than the AKI number. Though I believe standard regular in Europe is RON 95, equivalent to AKI 90-91. Also interesting is this was done in a GTI, which is a performance car, and they measured power and not fuel economy.

 

 

 

Definitely agriculture lobby, subsidies, etc. Also why HFCS is used so frequently instead of cane / beet sugar, even though there's evidence that it isn't healthy. Ethanol has the perception of being "green" / "renewable", but more diesel is burned in it's production (tractors, trucks), and petroleum based fertilizers used than energy is captured in the fuel. As well MTBE is / was used as an octane booster / oxygenate additive (promotes cleaner burning, lower smog emissions) post-leaded fuel, and MTBE is a carcinogen, and made its way into ground water. Ethanol is an alternative, again promoted by agriculture lobby. Other alternatives exist.

 

Good to know I never knew why their octane ratings were different over there. First time I filled up in Europe it confused me to find the regular haha.

 

I think they did performance because its a car show that usually does performance vehicle testing so it has the entertainment value. I would imagine that of you can get better mileage with the more powerful fuel.

[Poirot1959]

Good to know I never knew why their octane ratings were different over there. First time I filled up in Europe it confused me to find the regular haha.

 

I think they did performance because its a car show that usually does performance vehicle testing so it has the entertainment value. I would imagine that of you can get better mileage with the more powerful fuel.

 

All the reviews that I have read say that if you want to achieve the HP that Ford is saying the 2.0l ecoboost delivers then you need to use premium gas. And Akirby, you are right the spec for the fusion does not mention premium, But I sware I saw it originally in august when I was looking at the spec for the fusion.

[drolds1]

All the reviews that I have read say that if you want to achieve the HP that Ford is saying the 2.0l ecoboost delivers then you need to use premium gas. And Akirby, you are right the spec for the fusion does not mention premium, But I sware I saw it originally in august when I was looking at the spec for the fusion.

 

The official specs on the Ford Media site don't mention anything but the specs for the 2013 Escape with the 2.0 Ecoboost engine show 240hp with premium fuel. I can't imagine why it would be different for the Fusion. All the other engine specs are the same between the two. Further down in the chart, under recommended fuel, it shows 87 octane. Seems like sort of a contradiction to me.

Edited November 17, 2012 by drolds1

[BlackBetty]

Unless the Fusion has a different tune then the Ecape for whatever reason.

 

I would still refer to the owners manual and use whatever they recommend.

[ehidle]

There is absolutely, positively ZERO reason to run premium fuel in this motor. It has absolutely no benefit whatsoever.

 

The octane rating of a fuel is a measure of its resistance to spontaneous detonation at high temperature and pressure - basically higher octane fuel has a higher ignition energy. It is ONLY necessary when running in motors with a very high compression ratio, where lower octane fuel can spontaneously detonate as the piston compresses the mixture.

 

Any performance benefit you think you are getting from premium fuel in the 2.5 is in your head. And, in fact, higher octane fuel can actually reduce economy in a motor that doesn't have a high-energy spark, which the Fusion doesn't because they want longevity of maintenance and not super performance.

 

Oh, and as far as detergents or branding, most gas is 10% by volume of the best detergent in the world - Ethanol. Ethanol fuel will keep your internals spic and span, because it dissolves stuff very well.

Edited November 21, 2012 by ehidle

[Waldo]

There is absolutely, positively ZERO reason to run premium fuel in this motor. It has absolutely no benefit whatsoever.

 

Well that depends on which motor you're talking about. The Fusion has had so many different motors and calibrations over the years that this generic statement isn't always true. It is true of the early Fusions. In 06 Ford's strategies were tuned for 87 octane and would only back out timing if they detected knock. Putting in premium would not provide any significant benefit - except for the ethanol comments as noted above.

 

But around 2010 Ford came out with a more advanced powertrain control strategy that will actively "look" for premium fuel. It WILL advance timing if premium fuel is detected and it WILL provide slightly better efficiency and power (though maybe not enough to justify the higher cost). i'm not sure when this strategy made it into the Fusion, but I think it was sometime in the 2010 or 2011 model year and I think only on the V6, not the I4.

 

The new Ecoboost engines absolutely will make more power on premium fuel. These engines were designed in Europe with 91 octane and had to be "detuned" for North American 87. They use the advanced knock detection strategy and will pick up on when you have premium in there and they will adjust accordingly.

[Big Jim]

There is absolutely, positively ZERO reason to run premium fuel in this motor. It has absolutely no benefit whatsoever.

 

The octane rating of a fuel is a measure of its resistance to spontaneous detonation at high temperature and pressure - basically higher octane fuel has a higher ignition energy. It is ONLY necessary when running in motors with a very high compression ratio, where lower octane fuel can spontaneously detonate as the piston compresses the mixture.

 

Any performance benefit you think you are getting from premium fuel in the 2.5 is in your head. And, in fact, higher octane fuel can actually reduce economy in a motor that doesn't have a high-energy spark, which the Fusion doesn't because they want longevity of maintenance and not super performance.

 

Oh, and as far as detergents or branding, most gas is 10% by volume of the best detergent in the world - Ethanol. Ethanol fuel will keep your internals spic and span, because it dissolves stuff very well.

 

This post is so inaccurate in so many ways I don't know where to start. It looks like an oversimplification that went sideways.

 

Premium fuel does not have more "ignition energy" however you may define that term. Higher octane fuel has more detination resistance so that the burn (not ignition alone) is better controlled. It actually burns slower. The slower burn permits it to burn longer if it is ignited earlier in the compression cycle.

 

Ethonol is seldom a full 10%. It is up to 10%, and is often closer to 6% to 7%. It cannot exceed 10% if so labeled or 15% is so labeled.

 

Ethonol may burn cleaner (and when mixed with gasoline that may be debatable), but it doesn't do much to clean things. It does do a good job of absorbing any stray water in the fuel and some think this is cleaning. It is a double edge sword though as because it is hydroscopic (tends to absorbe water), if not handled well in the blending process it may actually bring water into the gasoline and if in enough quantity may tend to settle out. It is a real mess when it happens.

 

Higher octane fuel may help both power and fuel economy. Some engines are more responsive to the higher octane than others.

 

I will certainly agree that higher octane fuel often makes so little difference for the average driver that all it does is lighten his wallet.

[Monochrome11]

Big Jim, I agree with what you said with the exception of the slower burn of higher octane fuel. I know there is a lot of opinions on this but my opinion is it is just a more stable burn. Lower octane fuel can flash easier in a less stable burn and may seem to burn quicker in areas but I think the overall "complete" burn is done at the same time. I use 112 octane fuel in my 15/1 compression ratio race engine and get optimum power at 32 degrees full advance. When I first started racing I was running the engine with lower compression at around 12/1. I also ran lower octane fuel. Guess what, the optimum power was still at 32 degrees full advance. I could be wrong but that seems to indicate the burn rates were similar.

 

I know compression should have an effect on burn rate but I also know it is harder to get the spark plug to ignite the fuel at higher compression due to the increased density. A higher energy spark is needed by closing the gap or increasing the power to the spark plug.

[akirby]

I don't think there is any difference in how it burns - just how quickly it ignites.

[Big Jim]

Big Jim, I agree with what you said with the exception of the slower burn of higher octane fuel. I know there is a lot of opinions on this but my opinion is it is just a more stable burn. Lower octane fuel can flash easier in a less stable burn and may seem to burn quicker in areas but I think the overall "complete" burn is done at the same time. I use 112 octane fuel in my 15/1 compression ratio race engine and get optimum power at 32 degrees full advance. When I first started racing I was running the engine with lower compression at around 12/1. I also ran lower octane fuel. Guess what, the optimum power was still at 32 degrees full advance. I could be wrong but that seems to indicate the burn rates were similar.

 

I know compression should have an effect on burn rate but I also know it is harder to get the spark plug to ignite the fuel at higher compression due to the increased density. A higher energy spark is needed by closing the gap or increasing the power to the spark plug.

 

A higher energy spark is achieved with a wider gap. More voltage is required to fire the plug. Some explanation is needed.

 

The so called coil output is the maximum output, not the constant output. Maximum is just that, the maximum the coil can produce. When reading ignition on a scope, you can read the required voltage. Required voltage varies due to several factors. The higher the cylinder pressure the higher the required voltage. The leaner the mixture the higher the required voltage. The wider the spark plug gap, the higher the required voltage. When required voltage exceeds the coil maximum capacity, the plug doesn't fire. All of those things can be seen on a scope pattern. If the spark finds an easier path to ground, it will take it. If the plug wire breaks down, it is like an infinite gap and the plug won't fire. In years past, repair shops had multi-thousand dollar ignition testing scopes mainly to identify bad plug wires, a problem that went away when plug wires were upgraded to protect cat failure from misfires. I spent years reading scope patterns, a now useless talent. Those images are still burned bright in my mind though.

 

And yes, higher octane fuel burns slower. The molecules are larger and burn slower. Gasoline is a complex mixture of hydrocarbons. Hydrocarbons are unique in nature in that they can create variable sized chains of carbon. The chains are relatively easily expanded or contracted by synthesis or cracking. In a simplistic explanation, the ideal size for a gasoline engine is eight carbon atoms, and a fuel with 100% eight carbon chains is called 100 octane. There are actually several different molecule shapes in all sizes, including octane, as well as the fact that getting them to all be identical would be prohibitively expensive. Typical gasoline is a blend of many different sizes and shapes of hydrocarbon molecules, some larger and some smaller. 100 octane would have an average size that would make it behave like 100% eight carbon atom hydrocarbons. This blending varies on the season (more light ends in winter to help with cold starting), the crude that it was extracted from, and the equipment at that particular refinery.

 

It may seem hard to fully comprehend, but the slower burn provides better control of the burn if the engine is designed for it.

[Poirot1959]

Wow Thanks BigJim this is really informative.

 

very interesting discussion. I did learn a lot more. So in my case I will do real life testing. At this moment I am burning my first fuel tank with regular and since the car is brand new I am not really going to use this as my reference. But at this point I average about 50% city/50% Highway and I am up to 10.2l/100k so roughly 23.06mpg. Which btw is a lot better that my 2009AWD that had a average of 13.4l/100k (17.55mpg)

 

On my next tank I will still use regular and do some calculation. After that I will switch to premium for 2 tanks and will give you feedback. But my money is on improved mileage with premium. Now the question that will remain is: Will it be worth the difference in cost?

[akirby]

I don't think the difference in burn rate would be noticeable in terms of power or fuel economy. The performance benefit of premium comes from advanced timing and higher compression.

[Monochrome11]

A higher energy spark is achieved with a wider gap. More voltage is required to fire the plug. Some explanation is needed.

 

The so called coil output is the maximum output, not the constant output. Maximum is just that, the maximum the coil can produce. When reading ignition on a scope, you can read the required voltage. Required voltage varies due to several factors. The higher the cylinder pressure the higher the required voltage. The leaner the mixture the higher the required voltage. The wider the spark plug gap, the higher the required voltage. When required voltage exceeds the coil maximum capacity, the plug doesn't fire. All of those things can be seen on a scope pattern. If the spark finds an easier path to ground, it will take it. If the plug wire breaks down, it is like an infinite gap and the plug won't fire. In years past, repair shops had multi-thousand dollar ignition testing scopes mainly to identify bad plug wires, a problem that went away when plug wires were upgraded to protect cat failure from misfires. I spent years reading scope patterns, a now useless talent. Those images are still burned bright in my mind though.

 

And yes, higher octane fuel burns slower. The molecules are larger and burn slower. Gasoline is a complex mixture of hydrocarbons. Hydrocarbons are unique in nature in that they can create variable sized chains of carbon. The chains are relatively easily expanded or contracted by synthesis or cracking. In a simplistic explanation, the ideal size for a gasoline engine is eight carbon atoms, and a fuel with 100% eight carbon chains is called 100 octane. There are actually several different molecule shapes in all sizes, including octane, as well as the fact that getting them to all be identical would be prohibitively expensive. Typical gasoline is a blend of many different sizes and shapes of hydrocarbon molecules, some larger and some smaller. 100 octane would have an average size that would make it behave like 100% eight carbon atom hydrocarbons. This blending varies on the season (more light ends in winter to help with cold starting), the crude that it was extracted from, and the equipment at that particular refinery.

 

It may seem hard to fully comprehend, but the slower burn provides better control of the burn if the engine is designed for it.

Big Jim, Again I agree with most of what you say. You are very knowledgeable and I am not trying to compete against that. I am sure I would come out on the loosing end of that anyway.

 

I can't agree with the statement, "A higher energy spark is achieved with a wider gap". You can achieve a higher energy spark with a wider gap if you apply enough voltage but if you don't increase voltage you get a weaker or no spark at the plug when the coil fires with a wider gap. You can observe that by observing the color of the spark at different gaps. I think what you went on to say explains it though. You should understand why I have to use a 0.025" gap to get optimum horsepower with 15/1 compression ratio even with a higher voltage coil.

 

As to the chemistry lesson you left some holes. The number of carbons in the molecule is not the only factor that effects octane. Aromatics like toluene (7 carbons) has a high octane rating of over 110. n-octane the long chain version of the 8 carbon molecule is actually very low in octane. It is isooctane (a branched 8 carbon molecule) that is rated at 100 octane. Methane (a 1 carbon molecule) has a very high octane number at around 120 and hydrogen is even higher with no carbon atoms. This is by business, I have been a chemist for over 40 years. That does not make me smart it just means I have the tools to find this information easily.

[Big Jim]

Big Jim, Again I agree with most of what you say. You are very knowledgeable and I am not trying to compete against that. I am sure I would come out on the loosing end of that anyway.

 

I can't agree with the statement, "A higher energy spark is achieved with a wider gap". You can achieve a higher energy spark with a wider gap if you apply enough voltage but if you don't increase voltage you get a weaker or no spark at the plug when the coil fires with a wider gap. You can observe that by observing the color of the spark at different gaps. I think what you went on to say explains it though. You should understand why I have to use a 0.025" gap to get optimum horsepower with 15/1 compression ratio even with a higher voltage coil.

 

As to the chemistry lesson you left some holes. The number of carbons in the molecule is not the only factor that effects octane. Aromatics like toluene (7 carbons) has a high octane rating of over 110. n-octane the long chain version of the 8 carbon molecule is actually very low in octane. It is isooctane (a branched 8 carbon molecule) that is rated at 100 octane. Methane (a 1 carbon molecule) has a very high octane number at around 120 and hydrogen is even higher with no carbon atoms. This is by business, I have been a chemist for over 40 years. That does not make me smart it just means I have the tools to find this information easily.

 

I'm well aware that I left some holes in the fuel chemistry area. The rest of the chain and probably the shape of the molecule certainly has an impact too. Better controlled burn from slowing it down is something that was pounded into my head from my training as a tune-up mechanic many years ago. You get more push on the piston if you can light the fire sooner so that you are getting more optimal use of the fuel. You can't light it sooner if the fuel isn't up to the task and get max push before the piston crosses TDC.

 

The color of the spark is not a good indicator of the energy there. Attempting to tell the energy consumed by a spark plug out of the engine is useless. The dynamic conditions inside the cylinder change too much, both in fuel mixture (which can effect required voltage) and cylinder pressure which has a dramatic effect on required voltage. Reading the actual voltage as you can do with a scope tells a much better story. The main reason for .025" plug gap on an extremely high compression engine, and usually on artificially aspirated engines as well, is that the cylinder pressure under load can be so high that the coil can't fire the wider gap. The blown engines I tuned many years ago had a miss under load unless the gas was diminished. You would have thought that most shops that install blowers would know that, but that was one of the most common problems I had to correct after blower installation. That and the advance curve. If they were lucky the advance curve was corrected before they melted pistons.