Derf00

OEM Tune on 05-09 is for 87 octane (Except for Bullitt with dual tune). Zero benefit except for losing some weight...in your wallet...of cash...which I guess could mean there is a benefit to using premiumum without being tuned...less weight = increase of MPG of 0.0002 mpg...unless you use plastic, then said MPG gain is null and void.

JimC

Using a higher octane than you are tuned for will not "run cleaner" or cause you to get better MPG. Higher octane doesn't run cleaner, it just burns slower (which could lead to more deposits I suppose with an incomplete burn). With the push for auto companies to get the MPG averages up higher don't you think that they would be recommending using a higher octane if it would cause a significant increase in average MPG - those CAFE standards are pretty high.

This has been tested, and debunked, numerous times by different organizations (I think Mythbusters even did something on it). But the myth continues and people continue to spend the extra money because they have convinced themselves that it is better.

Go wash your car and give it good coat of wax. My butt dyno tells me that my car runs better, is quicker, and gets better MPG when it is freshly washed and waxed. Just as valid a test.

mustangspotential

I'm surprised there's still so much of a debate on this topic if there's been plenty of studies that a car designed to run on 87 does not benefit from putting a higher octane in it.

I know people that do this in their Hyundais and all and I'm just like....

157dB

OCTANE ratings are in direct relation to pre-ingition properties.
The higher the number the more resistant to pre-ignition (knock, ping).
Higher compression engines require higher Octane ratings because
compressing an air/fuel mixture produces heat. The more compression,
the more heat and the tendency of low Octane fuels to pre-detonate.

dcarlinf1

Just for argument's sake. How do you all explain this comment from Car and Driver magazine regarding the 2011 GT?

"The output of 412 horsepower at 6500 rpm and 390 pound-feet of torque at 4250 rpm (that’s with premium fuel; regular unleaded drops the figures to 402 horses and 377 pound-feet) is slightly less than the 426 horsepower in the Camaro SS and the Challenger SRT8’s 425. "


http://www.caranddriver.com/reviews/...ang-first-ride

rogan01

specifically stated - pretty sure in the owners manual - that 91-93 octane is required to get the 412 hp for the 2011-12. Otherwise you get about 9-10hp less. correct me if wrong.

I always use 93.

Derf00

Because 2011+ have dual tunes like the 08-09 bullitt. Simply put, when the computer senses a higher octane of fuel it changes the tune to match the octane. 05-2010 do NOT have this feature so it's a waste of money to put a higher octane without the tune.

Two totally different engine management systems not to be confused with one another.

Even with the dual management system on 2011+, the higest Octane rating recommended is 91 so, running 93 (when 91 is available) is a waste of money same as running 91 (or 89) in a car that is only tuned for 87.

dcarlinf1

Good explanation, thanks!

PNYXPRESS

This and also the higher the octane level the lower the heptane level, which is the reason for the premature detonation. Heptane will self detonate as soon as pressure is applied. Because of this, as soon you start the compression stroke it starts to detonate causing a downward force on the upward moving piston, causing the motor to work harder. By using a higher octane fuel you you lower the amount of heptane and lessen the negative force against the piston during the compression stroke which yields a higher mpg due to the engine not having to work as hard to obtain the same outcome.

I have ran multiple tanks of each grade thru my sixxer without changing anything but the octane fuel and I gained enough of a difference in fuel milage to offset the price difference from 87 to 89, however the gain from 89-93 were minimal and wouldnt offset the cost difference. my dad also did the same test and he now also runs 89 in his chrysler.

I never did the multiple grade test with my GT as I just run 89 since I bought it