I have a v6 and the manual recomends 87 octane regular gas but i found out my friends 94 z28's manual recomends 91 octane so i was wondering if the new Mustang GTs manual say the same or can you use regular?
....thanks

 

87 octane.

 

Regular ol' 87 is all she needs. Unless you have an aftermarket tuner, then you can pry some extra ponies from it with the premium gas. Otherwise, premium won't net you any gain in hp.

 

well thats good to hear ...i hope to get a GT soon and had the 91 octane thing been true about the GT's then that would have been the end for me as far as GTs go.....thanks!

 

This is the classic octane question.

I was told quite directly by the dealer before I took my Gt home to use 87 octane gas, not premium. I was a bit surprised because having owned 4 th gen camaro's and firebirds I found that the V6 models of those cars took regular gas and the High performance models specified premium.

The big difference has a lot to do with compression and engine timing. If you run high compression and/or lots of timing you're engine is more prone to detonation (spark knock). Since gasoline is less gas and more additives these days (read that=crap gas) Engines can be more prone to detonation than back in the day.

Since the average 4th gen Camaro or Firebird V8 model was running around 9 to 1 or more compression with aggressive timing from the factory premium fuel was necessary. The V6 motors could run regular but from experience I ran the "mid-grade" 89 octane in them once they past 80K on the clock. The V6 motors were easier to pull timing back on than the V8's so they could run cheaper gas even with similar compression ratios.

These days there's much more fine control of the fuel and ignition system than there was even 10 years ago. So if Ford says 87 octane they mean it. Otherwise they'd be changing lots of heads and pistons in warranty.

Running Premium in a car that doesn't need it is a waste and is really a false performance mod. In fact because there are so many detonation inhibitors in the premium gas you actually end up with more carbon crud in your combustion chamber because of inefficient burn.

Those guys who go buy the 105+ octane race gas at the local 76 station are most likely towing the car they're filling up with on the way to the race track. Ask them their timing and you're likely to hear 40+ degrees advance which is way more than any street car driven daily should ever run.

Oh yeah, and there's the 8 bucks a gallon and 1MPG too..

In short (too late for that??) Run what the book says.

 

I agree whole-heartedly with elcaminoguy. However, I have read in different places that the computer was tuned from the factory for 91 and they depend on the over-engineered knock sensors to retard the timing for 87. I don't know if this is totally true but it came from some of the more reputable tuners.

 

its entirely possible, I had a 2001 Toyota Celica GTS, the manual called for 96, which isnt available in cali, so I ran 91, the the timing and vvti compensated enough to never have an issue

 

That's true, The knock sensors are integral to the timing on those cars. Especially the V6 models that used a DIS ignition (No distributor, just 3 coil packs and cam and crank sensors) Too much detonation and the timing got pulled way back and usually threw a POxxx code.

 

Actually I was referring to s197s.

 

Well then, it seems some knowledge is indeed transferable! Good to know the bloody knuckles from all those years of dealing with the "Mark of Excellence" haven't gone to waste with the purchase of a real pony car!

 

Plenty of cars out there specify 91 gas, but also say you can run 87 at a reduced power output. If that was the case for the Mustang, why wouldn't Ford just say so?

In order for them to claim 300 hp and advertise the car to run on 87 octane only, it has to make 300hp on 87. If it made more on 91, why wouldn't Ford claim that? More HP = more sales.

 

I swear I've heard that an S197 GT makes approx 5 more HP if using 91-93 octane even without a tuner ???

 

The only thing running 91 octane does is makes certain you get no detonation. With no detonation, the knock sensors do not tell the computer to pull timing, ensuring you get the max HP. Running 87, there is always the potential for a little detonation, hence the engine pulling the timing to compensate.

It's not really that the engine is tuned for 91...just that it's tuned at the edge of 87.

 

Could be crappy gas. I've been using Exxon-Mobil religiously, just because it seemed like a big name and it's EVERYWHERE where I live in MD. But turns out the bad gas was the reason for the detonation in my Volvo and also for the detonation in my 93-tuned stang. 89 octane Exxon or 87 octane BP cured the detonation in my Volvo. 93 BP cured the majority of the detonation in my 93-tuned stang.

Now I stick to BP.

 

Use 89, you can hear detonation occasionally on the stock tune that the knock sensors catch nearly instantly,, but its there quite often. Plus, bad 89 still is well above the minimum octane. It hardly costs more anyway.

Don't confuse it with older cars whos carbon buildup would effectively raise the compression ratio enough to require higher octanes later in life. The computer is tuned to just barely let it use 87, like was said before. Its a 30k car, you wont buy Cosco cola over Coke, so why short that tiny bit of $$(much less then $2 per tank) for gas for your sports car. Do the math sometime versus anything else you buy in life, we have been trained to fear gas prices to the penny by the media. Skip a $5 cup of coffee before skimping on $1.45 for every 250 miles you get out of your car.

 

Well it didnt used to matter as much as it does these days. These cars are so computerized that if it is tuned for 87 then thats what you should run. You can cause pinging/detonation by running different octanes. Most of the time you will not notice, But it is not optimal running conditions. but If you want to run a different octane then you should get a tuner and cold air intake. Other wise I think you are just wasting your money on the more expensive gas.

 

you forget that more yuppies buy mustangs then true enthusiast, that being the case the yuppies would be turned off by a premium gas requirement so yes higher octane would mean more hp, but in actuality less sales

 

deleted.. Point: Higher octane does not result in more pinging

 

You only need the octane if your timing has a lot of advance in it. The PCM is going to adjust it with the knock sensors anyway. Higher octane doesn't mean rocket fuel, just that it's more resistant to detonation. If you run premium in a car that doesn't need it you end up with crud in your combustion chamber and possibly a plugged up catalytic coverter over time because the fuel is actually less volatile which makes for a dirtier burn.

Cars that need premium usually have more advanced timing, higher compression or run hotter so they require premium which allows you to have more timing with less detonation because the fuel isn't igniting so fast.

If you put premium in a car that doesn't need it you end up with more unburned fuel at the end of the combusion cycle. Eventually that will build up on top of the pistons and in effect shrink the combustion chamber volume which causes higher effective compression in the chamber but not in a good way. Preigntion from the crud on top of the pistons and higher cylinder pressures make it a pinging puddle jumper in no time..