94 octane vs 87 octane?!?

[5spd Z71]

Unless your truck is tuned to run on ethonal, youll loose power and mpg's. These trucks are only designed to run with 5-10% ethonal, and some gas stations have more than that mixed in the gas. Which will eat up almost everything non-metal in your fuel system, and cause your truck to run like ****.

 

[The big beast!]

So if I use ethanol free gas my truck should run better?

 

[5spd Z71]

Yes. If you can find a station that sells it. However dont expect results right away. Itll take a few times of filling up to use all the old gas that has the ethonal.

 

[Tempted]

94 has the potential to burn hotter, creating more power. Remember, power(energy) is only heat. Hotter = more power. BUT.... running higher octane fuel won't help a vehicle unless tuned to run on it. It absolutely will not burn up your valves or cause any other premature failure but it won't help you either. When you tune for higher octane you lean out the mixture. Since it produces more energy per part you don't need as much. That is where the benefit comes in. But if your computer isn't tuned to reduce the injector pwm or advance the ign timing then you are just wasting money. Now if you think you got bad gas somewhere then mixing it with high octane can help to restore some power.

 

[Aloicious]

+1 on what temped said, with a small addition...Tuning for higher octane is not so much about leaning out the mixture as much as it is about spark advance, higher octane fuels resist detonation, you don't really get any more power from higher octane fuels vs lower octane fuels, you get the power from the advance in the spark maps, and the higher octane fuel is able to run the higher spark without detonation. (if you want to read up about WHY higher octane resists detonation, look up the topic of activation energy, I won't bore everyone here with my science geekness)

everyone has already mentioned a tune requiring higher octane, which is simply a tune with spark maps adjusted....but higher octane fuels are extremely useful for engine setups that have a higher likelyhood of detonation (or ping)...things like increased compression ratios and forced induction for example...

like has already been mentioned, running a higher octane when not needed will not give you any more power, or economy, etc...it will give you a lighter wallet though...

 

[Aloicious]

also worth noting, even if your truck IS tuned to run ethanol, you still will have reduced MPG, this is because ethanol is less energy dense than gasoline, meaning that MORE will be required to make the same amount of power, no matter what your tune is....if you find a flex fuel vehicle and compare it to an identical but non-flex fuel version, there will be a few differences, the main one things being the flex fuel injectors will be higher flowing injectors, to help compensate for the higher volume of fuel needed to make the same power (among other things like stoichiometric values what I won't get into here)....but regular vehicles are able to tolerate a small mix of ethanol, like the E10 (10% ethanol) mixes, without tunes because the O2 sensors will be able to compensate enough...

 

[Tempted]

+1 on what temped said, with a small addition...Tuning for higher octane is not so much about leaning out the mixture as much as it is about spark advance, higher octane fuels resist detonation, you don't really get any more power from higher octane fuels vs lower octane fuels, you get the power from the advance in the spark maps, and the higher octane fuel is able to run the higher spark without detonation. (if you want to read up about WHY higher octane resists detonation, look up the topic of activation energy, I won't bore everyone here with my science geekness)

everyone has already mentioned a tune requiring higher octane, which is simply a tune with spark maps adjusted....but higher octane fuels are extremely useful for engine setups that have a higher likelyhood of detonation (or ping)...things like increased compression ratios and forced induction for example...

like has already been mentioned, running a higher octane when not needed will not give you any more power, or economy, etc...it will give you a lighter wallet though...

^^^ That. But an economy tune does lean it out without increasing the ignition timing significantly. Running a fuel with a high resistance to detonation means you can run at 15.5-16/1 AFR and sometimes higher while making the same amount of power. The higher the AFR, the less fuel.

A performance tune is normally where you advance ignition timing beyond what lower octane fuel can handle while still introducing the same amount of fuel. But advancing the ignition timing means the charge will be more compressed when ignited, causing a more violent reaction when spark is finally introduced.

 

[Aloicious]

oh yeah, totally. I was mainly referring to a performance tune in my post. higher octane fuel helps in both situations.

typically mail order economy tunes don't lean it out too much, for safety, in order to do lean it out properly the tuner needs to be with the vehicle, and with at least 1 wideband O2 sensor, and preferably a load bearing dyno too.

 

[Tempted]

Well to be truthful with you a canned tune isn't something a tuner sets up. Most tuning software comes with pre-loaded files for any given PCM code. These "tunes" are based on bone stock engines and are simply slight adjustments in the fuel and ignition tables and removal of the factory set limiters(vehicle speed, rpms, PATS codes). And unless you take your vehicle to an excellent tuner with a dyno these canned tunes are better than most files that a tuner can draw up based only on numbers. They were written by tuning gurus who spent thousands of hours developing the best possible SAFE parameters. I've got a folder of base tunes I wrote for the most common engines(Ford 4.6 SOHC and Intech mod motors, Triton motors, new Chrysler Hemis and of course the B, D and H Honda motors). I use these as starting points and after learning what the customer has done to their vehicle I adjust where I see fit. I hate canned tunes but since nobody wants to bring their cars to me I have no choice but to send out something I can't test. EVERY tuner will have a clause somewhere stating we are not liable for damage due to a mis-adjusted tune. The reason isn't because we are scared our tunes are fouled, it is because in my experience over half of the customers are lying about their vehicles mileage and the mods performed. If I see a 250k mile B16 with a stock, unported head and exhaust manifold I'll reduce the aggressiveness of the tune. Since those ricers want all the power they can get, they lie to us and we end up sending them a tune with the probability of damaging their junk. If any of you have experience with them you know how weak and pathetic the timing belts are. Well they are supposed to be changed every 80k. The idiots ricing them out NEVER change them. Now I send them an aggressive tune that alters the Vtec ramping and boom, the 250k mile belt pops. Since they are interference motors, the pistons slam the valves and it all snowballs from there. Now they call back and say I owe them an engine because the tune killed their car.

 

[slowburb]

Ethanol does terrible things to the parts its comes in contact with. If leaves a gooey sticky residue behind, and is very "hot"...meaning it "cooks" things like rubber/plastic lines and gaskets., and there's plenty of parts like that in your fuel system. It is not meant for gasoline engines. Beyond and above everything else, corn is food, not fuel.

Anyways, octane is a fuel's resistance to spontaneous combustion. The higher the rating, the higher the combustion point. If an engine is set up for an aggressive spark lead and cranks high compression, putting lower octane fuel in it will cause the a/f mixture to explode before it is time, when the piston is in the wrong place. An engine set up for lazy spark lead and low compression is given hi-test fuel, and all of a sudden it is fouling plugs, running rich, sending raw gas into the cats, because the spark and compression aren't igniting all of the fuel before it leaves the chamber.

Run 87.