My co-worker has run 87 in his '03 5AT Coupe for years and says he doesn't have any problems with it although he has never given it more than half-throttle and isn't the kind of guy that would probably detect engine noise...

I on the other hand purchase 91 Octane since that's what they offer in Phoenix but I drive a little harder than him from time to time.

 

I know on my bike I gain a extra 8hp an that was a half 110/91, I'm gonna dyno the G next

 

Because of the poor quality fuel available in CA (needed to meet strict emissions standards), I use in both my cars, every other oil change.

I run 91 octane, Costco gas, and honestly can not tell the difference between name brand gas (name brand = specific additives, nothing more) and Costco gas. I have tried hard to justify the extra 20-25 cents per gallon for Chevron (after you apply the 2% Costco Amex discount), but simply cannot. Some of the local grocery store gasoline points help level the playing field, but even with those, Costco normally wins on price and I'm not restricted on where I can buy groceries.

I have lived in other states like TX with the same car, and have to say that the car runs noticeably better on Texas fuel as compared to CA.

 

You can use 87 and it probably wont hurt anything but it will retard the ignition timing and hurt horsepower and fuel economy. where I live premium is only like 30 cents more so its really kind of dumb to use regular because its only like $5 extra if you're completely empty and you get better gas mileage so you use less of it.

 

What I have often wondered is if your mileage will actually improve slightly (under normal driving conditions) by using lower octane fuel? For instance, if I am causing my timing to retard slightly to accommodate detonation that could occur, wouldn't this use more conservative fuel maps/timing as a result, improving mileage? Obviously, timing closer to Top Dead Center improves power, so this will not yield the best overall performance, but it seems at least on paper that mileage should improve.

 

A couple years ago I contemplated getting dyno tuned for 87 octane because that's when the Mustang and Camaro came out rated ~300 crank hp with unleaded regular gas. It's not like I would come close to that rating because those cars have bigger engines with direct fuel injection. On my usual 93 octane my navigation says I get 19.2mpg doing my usual daily suburban driving. I got a little over 20mpg during the early spring when temps were highs of 50s.

 

Trust me you get worse mileage. when I first got my car my dad decided to fill it up for me he put 87 octane in it. I drove like a grandma and got alot of people getting mad at me with how slow I took off from stop lights and such. I got about 18 mpg give or take. I ran the tank dry (which isn't a good idea by the way), and then filled up with 93 octane, and drove like a normal person got about 20. The thing is that with the ignition retarded to keep the high compression engine from detonating, the engine performance is hurt pretty badly, and it takes more to get the car going at speed.

 

The more u use 87 the lower ur tolerance builds against pinging with high octane.

 

I've been running 3/4 of a gallon of E85 per 1/4 tank then topping off with Chevron 91... made a big difference, no ping and better throttle response BUT mileage went DOWN about 2 mpg. But then again I didn't buy it for feul economy!

 

how has your engine fared using the Ethanol?

I hear a lot of rumors about it slowly destroying engines that weren't built for it, but they were all rumors, so I don't know how much you can trust them.

 

At $4.26 a gallon, I'm putting down ~$65 for a full tank. WTF

 

Your average passenger car that requires premium is tuned for 91 octane since that's the highest octane you can get in many parts of the country. Using higher octane is just flushing dollars down the toilet. Even using 93 octane over 91 octane is a waste of $$$ on your average stock unmodified car (by that i mean no power adder, compression bump or custom tune).

Fuel octane levels need to be compared to oil viscosity. Each engine has a specific requirement and changing the fluid doesn't generate the power, it merely allows the engine to achive 100% potential. Too many misconceptions these days about higher octane gas being "better" and making more HP. Too many variables to make a blanket statement like that.

For your average, stockish, street driven car, stick to what's in the owners manual. The engineers who designed your engine trying to wring every bit of HP and fuel economy out of it know what they are doing.


BTW, i think Sonoco 110 is leaded gas. Might want to be very sure before pumping it in. Works great in a carbed race car with no converters, but you don't want leaded gas in your emmissions equipped street car

http://www.racegas.com/fuel/1

 

thanks to all who responded.

Here it doesn't really matter it's a Premium (91/95) or Super (93/98) = they cost roughly the same 1,27$ and 1.3$ per-liter.

Very interesting is that MPG was a little bit better with Super 93/98 fuel, than Premium 91/95.
Also performance got better (perhaps it's psychological )

 

Yeah my choices are 87 89 or 93 so I always use 93 and my car runs beautifully, and I never have the pinging that people have even when they are using 91 octane, which is their premium. Either way you definitely should not use cheap gas or race gas, just use premium 91/93 octane gas and you'll be fine.

 

When I was back in TN it was 93 but now since Im stationed here in AZ I use 100 or 100/91 mix or sometime 110. When I use the 110, my car reacts like I am back at sea level. But I am built and boosted so I have felt the change just between locations.