is 91 octane better than 93 octane

[tritonman5.4]

i see alot of people with modded cars and trucks use 91 octane instead of 93.especially turbo'd SC vehicles.is 91 better for force inducted cars???

whats the difference?

 

[panda24619]

heres a big difference price and availability. i know i run my truck on 89 octane. there is 91 availability. i havent seen 93 around San Diego. but i do know a few places that sell 100 octane for $8 a gal.

 

[alexhozee]

In theory your car would drive better and use less fuel with 93.
The higher the octane the better the ignition in the cilinder.

In practice you should almost not be able to feel the difference between them.

Alex

 

[tritonman5.4]

i run my expo on 93 it runs alot better now i use to run 89 octane didnt feel to different from 87..im just not to familiar with 91 and not many gas stations carry it.i know sunoco carries it for sure.

 

[walnuts4x4]

but why would ford say to run on 87 octane? just a thought... 91 or 93 is just a waste of money in a stock motor

 

[mmrseed]

93 is only better than 91 if it is necessary because a custom tune dictates such. But if a vehicle needs 91 octane running 93 will contribute nothing except higher cost and neither are necessary if you run a stock motor expy which only needs 87

 

[Expedition]

I run 89 but that's because I'm tuned for it...

 

[panda24619]

i only run chevron 89 cause i can get 11 mpg out of it. any other octane and any other company i get 10 mpg. i know not a big difference. but i have the bigger 30 gal tank. so thats an extra 30 miles i can go.

 

[ELVATO]

I run 93 cuz I'm tuned for it. 93/91 in a stock engine is a waste.

 

[GDDYUP]

Here's the deal with octane. The higher the octane rating, the slower the fuel burns inside the cylinder. There was a study done many years ago on Ford Taurus' concerning octane ratings and the result of those ratings on the internal structures of the engine. The study compared the engines in Taurus' that were owned by privtae individuals and those owned by rental companies such as Hertz, Enterprise, etc. Engines were torn down and results were tabulated. What was found was that there was MORE sludge and carbon build-up in the engines owned by private individuals as compared to the engines owned by rental companies. The rental cars' engines were in much better shape internally than those owned by private individuals. Why you ask? What it came down to was the fact that the Taurus engine was designed to use 87 octane fuel. Private parties were filling up with higher octane such as 91/93 octane and rentals were being filled with 87. No one is going to pay a premium to fill a rental car with "The Good Stuff". People who owned their car were going to fill it with "The Good Stuff"..... Those who owned their car thought they were doing the right thing by filling up with a higher octane when in fact they were actually hurting their engine by doing so. The higher octane was burning slower in their engines which were designed for 87 and the result was a slower burn and more carbon/sludge build-up. In an engine designed to run on 87 octane, a higher octane does nothing more than create bad news on the internals.

Short and sweet. You really gain nothing from running anything other than 87/89 octane in your everyday Expy regardless of year. I have an 07 Limited EL. I feed it either 87 or 89 depending on what gas station I stop at. I NEVER feed it anything higher than that. Anything higher is a complete waste of money and it hurts my engine in the long run. The only reason to run a higher octane rating is if you have an engine that is desgined or modified to use that higher octane rating. The only real-world exception to that rule is if you run a programmer that is specifically set up and specc'd out to use the extra octane and even then it is going to be right on the edge unless you have modified your engine setup in such a way that the higher octane rating is neccesary to prevent detonation or to achieve a certain power goal.

Case study for octane : I use to run a 90 Mustang Notch at the drags up here in NH. The car was set up to run 87 octane. We're talking custom cams, ported intake/heads, long-tubes with single cats into 2.5" custom exhaust. Anderson PMS laptop ECU system and everything you would possibly want in a street/stirp car. I drove it to the track, ran it, then drove it home. With a 1/4 tank of 87 the car ran high 11s almost every single time if I did my part. Put 93 octane or race fule in it, 1/4 tank, and the car ran low to mid 12s every single time when I did my part...

Scientific? Hell no. But enough to prove the point of my instructors back in college. Octane means nothing more than the number prescribed in your owner's manual. Modify your car/truck far enough outside the boundries set by the manufacturer and THEN you have some thinking to do in regards to what your engine needs to be happy.

An aftermaket "intake" and some aftermarket "exhaust" is not going to give your ECU fits in it's stock configuration. Add a tuner with some custom fuel maps and such and then *maybe* your setup could take advantage of some extra octane. Maybe.....

Until you reach that point, spend your money on making sure your oil changes are up to date and buy a can of fuel system cleaner every oil change. THOSE are the simple things that make big differences down the road.