keerf

Hi All,

I have what I'm sure is going to sound like a dumb question.

I just bought a new 2011 v6 mustang a few weeks ago. For my first two fillups, I've put in plus grade fuel (aka 89 octane). I know my car is rated for 87 and it says so to use that in the manual.

Being that this is the break in period of the car, is using a higher octane fuel going to hurt my car? Should I just revert back to 87 and not worry about it. I seem to read conflicting reports here onthe web from various forums that higher grade octane can or won't hurt your engine and performance.

Any help would be great.

Thanks all!

MU71L4710N

waste of money unless your tuned for higher octane gas...

wikipedia fuel octane

Snakebite64

Wasting money is never a great idea

GreyStang

All those conflicting reports are probably coming from people blindly pushing the myth that "the higher the octane the better" It isn't true.. just use the octane recommended in your owners manual, UNLESS you've modded your car then it can change.

keerf

Ok, I will switch to 87.

But I guess my original question kind of remains un-answered. Using the higher octane, it won't damage anything though correct? Cause I've only done 2 fillups so far, and used higher octane on both those fillups.

Thanks for all the help.

GreyStang

Using WAAAY higher octane than required can & will harm your (stock) engine. But 89 is close enough to 87 that it probably won't matter,, you're just wasting money for no advantage.

mestit3

yepp.

dastangman

To add to people who have posted, rather than just agreeing, I wanted to state why it's a waste to buy higher octane. I use a higher octane gas in my daily driver all the time, haha...in Iowa our Super Unleaded 89 is about 10 cents cheaper than the regular 87. That's because it has ethanol in it and has been subsidized by our government.

A.) Yes, this is the break in period, and refer to your owners manual for details, but it's really the oil that's going to affect the break in period. Most cars these days are basically already to go for the most part, some even built to use synthetic oil for the break-in, but you'll have to check. Anyways, to my knowledge, your fuel (unless again your tuned for something specific) isn't going to have an affect on your engine break in.

B.) And here's why...octane rating is only a "measurement" of a resistance to detonation. A car with a high compression ratio, advanced timing, superchargers or a variety of other stuff, usually in the performance realm, will require premium because the chance of detonation and blowing a piston is much higher. And even if a car could use regular, especially those with knock sensors, a lot of manufacturers probably just stamp on to use premium as an insurance of sorts in case something could go wrong.

So, yes there's no added cleaning benefit, better gas mileage benefit, and the only performance benefit is that you're able to have more potential without having detonation. In other words, with premium you can have superchargers, higher compression, etc and because of this you can have better performance. There's a good chance that someone who says their car performs a lot better with premium is probably only mentally thinking this. The only thing I could see is a car that's been running regular instead of premium and that has knock sensors, may have been electronically cutting back timing and reducing performance, so that when they do fill up with premium they are getting a performance boost, but in that sense, they're basically tuned from the factory for it and by using premium you aren't improving performance, but rather by not using premium you'd be hurting performance.

Anyways, you're wasting nearly 13 cents a gallon around these parts if you're using premium.

bigjohnstud4200

on a different note, how is the new v6? have you raced any older generation stock gt's?

CopNaStang

The new GT's lose 11hp if premium is not used, but it may call for premium.