Question about 3.6L v6

[LarryB]

I had a long highway trip and decided to run 87 on one tank and 91 on the next. Fuel consumption was within 0.5mpg. I always figured that it was more important to buy fuel from a good retailer than the octane, unless your car specifies it.

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[Dan M.]

Like those above I've used 87 in all my vehicles including my current V6 Jeep and never had a problem. I don't believe there is a benefit to using higher octane unless the vehicle specifically calls for it or says something like " for optimal performance use" a higher octane.

 

[roaniecowpony]

I run 89 and do more short distance driving. Probably nonsense, but I do feel a slight difference in running 89 vs. 87. Likely a placebo.

Maybe not. These engines have computers to control timing and mixture. Could be a bit of extra power in there.

 

[openingshok]

A little lesson on gas grades for you. Octane isn't a performance enhancer. Octane is actually an ignition retarder. The ONLY reason to use higher octane gas is for engines with higher compression values. Diesel engines ignite due to very high compression values in the cylinder. There is no spark plug. Some sports cars that run on gas have VERY high tolerances so their cylinders see higher compression values. Regular gas in a high compression cylinder will ignite from pressure before the spark plug fires. So fuel manufactures add octane to raise the ignition point of the gas to a higher compression so the spark plug can ignite it before the pressure. So what you have read in the manual is correct. Higher octane does absolutely nothing in a standard compression engine such as the 3.6.

Look at it this way. If you add salt to water you lower the freezing point of the water. If you don't intend to use that water in temperatures lower than 40° the salt isn't adding any value to the water. You are just spending more money for salt you didn't need.

 

[jeepoch]

Maybe not. These engines have computers to control timing and mixture. Could be a bit of extra power in there.

Again, the amount of energy in any tank of 'quality' fuel is exactly the same independent of octane. Octane is simply a measure of a fuel's flash-point (the temperature and pressure at where it will ignite). The higher the octane rating, the more consistent it's flash-point and the easier it will be for the engine controller to maintain and predict the spark timing position (relative to 'top-dead-center' of the piston).

Any extra 'power' comes from the ability of the engine controller to deliver the most optimized combustion event under every operating load or condition. Using a higher octane fuel simply just 'helps' the combustion prediction algorithm's ability to calculate an optimal solution for both this as well as the next piston's detonation equation.

With a lower octane fuel the engine controller's solution to this equation is more dynamic (constantly changing) simply because the fuel's flash-point is less consistent and much harder to predict.

Jay

 

[blnewt]

I wish we had pure gas available here, that ethanol filler is a mpg killer, at least in all the vehicles I've owned. If I can find non-ethanol on our road trips I seek it out, always noticeable mpg increases without that corn crap!

 

[jeepoch]

I wish we had pure gas available here, that ethanol filler is a mpg killer, at least in all the vehicles I've owned. If I can find non-ethanol on our road trips I seek it out, always noticeable mpg increases without that corn crap!

Brad,

Totally concur. I've personally never considered Ethanol laced fuel to be good let alone 'quality' high or otherwise.

But alas, you have to use what is locally available. But don't get me started on the seasonal fuel blends. It seems like everything they sell within all urban areas are contaminated with some environmentally subjective additive.

Without the benefit of modern engine control computers, this crap they now sell would barely run any vintage carbureted contraption.

Jay

 

[QwikKotaTx]

The premium gas blends have very good additives that help lubricate and clean but on engines that only require 87 octane you can add a fuel injector cleaner when you fill up such as Lucas brand that also provides upper cylinder lubrication for the valvetrain as well as pump and injectors.

 

[roaniecowpony]

A little lesson on gas grades for you. Octane isn't a performance enhancer. Octane is actually an ignition retarder. The ONLY reason to use higher octane gas is for engines with higher compression values. Diesel engines ignite due to very high compression values in the cylinder. There is no spark plug. Some sports cars that run on gas have VERY high tolerances so their cylinders see higher compression values. Regular gas in a high compression cylinder will ignite from pressure before the spark plug fires. So fuel manufactures add octane to raise the ignition point of the gas to a higher compression so the spark plug can ignite it before the pressure. So what you have read in the manual is correct. Higher octane does absolutely nothing in a standard compression engine such as the 3.6.

Look at it this way. If you add salt to water you lower the freezing point of the water. If you don't intend to use that water in temperatures lower than 40° the salt isn't adding any value to the water. You are just spending more money for salt you didn't need.

Just to level set, the Pentastar is an 11.3:1 compression ratio. Running it on 87 is no small accomplishment for FCA. I'm sure they have maximized the squish area in the pent-roof chamber in order to run 87 in such a high compression engine.

To say that there is no gain from using a higher octane, you'd have to know that the engine is able to run at the maximum spark advance limit programmed in the ECU for ideal conditions. We all know that in hot weather with a hot intake charge and a heavy enough load, an ECU controlled engine will likely have to pull back spark advance. This is where a higher octane fuel would allow the spark advance to run at higher values and develop more power.

 

[openingshok]

Just to level set, the Pentastar is an 11.3:1 compression ratio. Running it on 87 is no small accomplishment for FCA. I'm sure they have maximized the squish area in the pent-roof chamber in order to run 87 in such a high compression engine.

To say that there is no gain from using a higher octane, you'd have to know that the engine is able to run at the maximum spark advance limit programmed in the ECU for ideal conditions. We all know that in hot weather with a hot intake charge and a heavy enough load, an ECU controlled engine will likely have to pull back spark advance. This is where a higher octane fuel would allow the spark advance to run at higher values and develop more power.

That's fair, but that's probably not power you're going to feel in the pedal. We're probably talking slide rule increases here. Certainly not worth the increase in cost of 92 octane

Just to level set, the Pentastar is an 11.3:1 compression ratio. Running it on 87 is no small accomplishment for FCA. I'm sure they have maximized the squish area in the pent-roof chamber in order to run 87 in such a high compression engine.

To say that there is no gain from using a higher octane, you'd have to know that the engine is able to run at the maximum spark advance limit programmed in the ECU for ideal conditions. We all know that in hot weather with a hot intake charge and a heavy enough load, an ECU controlled engine will likely have to pull back spark advance. This is where a higher octane fuel would allow the spark advance to run at higher values and develop more power.

Fair enough, but you'd need a dyno to see the benefits. You're certainly not going to feel it in the seat

 

[Thane]

You definitely will feel the lower power at performance limits, like towing up a grade.

It will also show in long term MPG. May or may not make up the price difference. It will also extend range.

 

[Steph1]

From time to time, I put-in a few consecutive tanks of Premium and the engine does run noticeably smoother.

However, with the gas prices currently spiking and will be getting even worst by this summer, I’ll be a good while before I use super again. Other than running smoother, I never noticed better fuel economy.

 

[Old Dogger]

87 Octane is all that is needed. As for additives, of which I have never been a big fan of. But, every 5000K, I do add a bottle of Chevron Techron to my gas tank. I feel that it helps to keep the Fuel Injector Nozzles clean.

 

[BRuby]

Chevron 87 with Techron has never let us down. JL or otherwise. Always is our first choice. No ping. No knock. Never had reason to use anything else.

Chevron high test is excellent if you have a vehicle that calls for 92 and up. Ethanol free. Quality fuel for very high performance engines. Chevron diesel is also an excellent fuel.

We use all 3. We recommend all 3.

 

[1BadManVan]

Chevron 87 with Techron has never let us down. JL or otherwise. Always is our first choice. No ping. No knock. Never had reason to use anything else.

Chevron high test is excellent if you have a vehicle that calls for 92 and up. Ethanol free. Quality fuel for very high performance engines. Chevron diesel is also an excellent fuel.

We use all 3. We recommend all 3.

Chevron is generally our go to fuel, sometimes shell if we are out somewhere and thats a good back up option.

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