Does the kind of gas make a difference? (87 89 91 93)
 

So I am working for a real estate company doing landscaping and have to use my own car. Because I go to different places throughout the week they give me one free fill-up. This got me wondering, would using 89 or 93 octane fuel benifit my 1999 GL 2 door with 164,000 miles in any way? More gas mileage? Better for the engine or any other of the cars components? And if so, which type of fuel would be best to use? Thanks for your time guys.

No. Do you know what the octane rating means? It's a measurement of the fuel's resistance to burn. You increase the octane, it slows the burn down, and reduces its tendency to self-combust under pressure/heat. It's for high compression, turbocharged or supercharged engines.

If the car is not tuned for it (raising the spark advance), it will make zero benefits for you. The car is tuned from the factory to operate at its peak efficiency on 87 octane.

from my experience higher octane gas gets eaten up faster

/\ +1 Yup, just stick with the 87 or the 89, whichever the local gas station carries. That's what the Alero was built to use. If you feel like it, just get a bottle of octane booster or carb cleaner and run it through your tank every now and then.

EDIT: I was replying to ION here, couldn't type fast enough...

Octane booster is known to increase the octane by 0.5 points or less. Not worth it. Only good thing I'd suggest you can run to clean your fuel system is a little methanol (fuel injector cleaner).

I don't really run octane booster often. I usually just get a bottle of STP complete fuel system cleaner every time I change my oil, sometimes more than that.

Yeah it makes a difference.

You car is programmed to run on 87, you can run 89, 91, 92, 93, or 94, but the higher you go the less MPG you'll get and leave more carbon in the motor. Over time the carbon can foul the plugs and clog the cat.

Once you mod, and seroiusly mod, not just intake and exhaust, an increase in octane may be neccessary.

I have the reprogramed PCM in my car. It's programed to run on 91 or better. I go to Sunoco since they have the 91, I get 1 to 3 MPG better on 91 than on 93 ;)

so if i get 89 instead of 87 it won't give any benifit at all? No better mpg or cleaner burn or make my engine run better since it has such high mileage? What I am getting from your posts is that anything other than 87 will do more damage than good... but I have gotten mixed replies on this in real life. Some people say I will get a little better mpg and it is better for my car since it has high mileage. Then some of you say it will hurt more than help... I figured at worst it wouldn't help any but wouldn't hurt either but I guess I am wrong. So the concensus is to stay with 87?

stay with 87...

Only time you need higher than 87 when its not recommended, is to smooth out engine knocking, and if you were experiencing that then you would know it.


Just use quality gasolines like BP or Shell. And if you want fuel injector cleaner, some gas stations now have gumout at the pump, where it charges $1 to start your gas fill with a dispensal of fuel injector cleaner. Not something I would do on my own dime, but if you're getting it paid for than why not.

you will experience no improvements by running higher than recommended octane.

there, simple answer

A little info on fuel injector cleaner, that flashy stuff that says it has "Jet Fuel" init, real jet fuel is JP8, a low grade diesel.

I run the 89 w/ ethanol in the alero, but that is because it's 10% ethanol, that goes to farmers here in America instead of oil barons in the mid-east, never had a problem with it. I know my newest car will vary the timing based on feed back from the knock sensor. Basically, the higher the octane the more timing it gets. I don't think the Olds is that smart though.

i have a 2003 GL coupe and i use 89 frequently(70% of the time i use 89)

i actually do have a findings of better gas milage. first off im a type to adds MMO(mystery oil) to my gas every time i fill up. with that i wanted to use 89 vs 87 cause im using a gas addative and its usually favored to use 89 when you use a fuel injector cleaner or etc. (my car has a K&N cone air intake FYI)

when i use 87 i actually notice i hit a half a tank about 150 miles on trip. this is with MMO in gas. now when i use 89 i hit a half a tank in about 165. its also a difference of 26 vs 28 mpg when i pump and do the math.
for you MMO haters: (my motor runs smooth with MMO, i can tell when i forget to add it in and end up adding it to my gas when i park it anyways, reduces motor shutter and lubricates fuel system parts, biggest difference is my steering wheel isnt vibrating when i start up the car, with the 4cyl its got a shutter on start up)

my drive to work is i hop on a straight 55mph road and drive it 15mi. then it drops to 45 and red lights for about 5 miles til i park it. aka casual care free driving thats not beating on my alero.

thats my findings, thats all it is, dont start a back n forth or pick me apart cause i wont humor you and will ignore you.

in all honesty dude, not to sound rude or anything like that at all here... but with you running 89 and MMO, your overall costs to get an extra 15 miles is not worth it IMHO...

I did the experiment too when I was younger with running the higher octane to improve mileage and while it did improve it slightly, the overall costs increased because of the higher price of the higher octane gas...

In a late model fuel injected engine running a different octane makes no difference at all. The PCM just compensates for the different fuel. I have noticed a difference between running ethanol blended fuels and just regular gas but I live in Nebraska. My 3.4 alero seems to run better and get better mileage without running the ethanol fuel. It's not a drastic difference but just a little difference

Like I said 5 years ago above, if the car isn't tuned for it, there are no benefits.

87 to 89 is not a big jump, you won't be able to compare results without every other driving variable affecting them.

Put 110 in and tell me you get better mileage.