Better gas mileage [Archive] - Forum


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grand am QT
02-11-2005, 10:39 AM
how to get better gas milage. my car gets about 10-12 miles to the gallon and im gonna be starting college in the spring which is a 20 or so mile drive everyday. my dad keeps telling to me get a 4 knocker and i dont want to i love my car. so if anyone knows how to gwt better gas milage on a 1992 grand am GT 4 door it would be much appriciated.

also. my exhaust is shot. but i love the way it sound it sound like a truck and i was wondering if there is a type of muffler i can get that wont decrease gas milage but make it sound good. but not like a eruo piece. also the tail pipe the stcok one from a 92' gagt. so if anyone knows your help would be very much appreciated.
i get my license back march 5th!

02-11-2005, 11:06 AM
Better gas mileage = Don't slam on the gas. Get a tune-up. New plugs and wires.

I don't know of any aftermarket mufflers are available to the 92 model.

02-11-2005, 11:23 AM
Since your car is quite old, I would recommend getting it completely tuned up and running as smoothly as possible. Drive lightly and think about your mileage every time you want to floor it. Mufflers aren't known to increase gas mileage all that much, so just get one that works right.

02-11-2005, 11:25 AM
your exhaust is why your getting 10-12 mpg and a tune up would help. a hole in your exhaust would screw with you gas mileage

02-11-2005, 01:46 PM
I would change your air filter while you are at it unless it was recently changed, it is part of the problem if the one in the car is clogged. My moms car went 50,000 with a filter once and was wondering where her performance and gas mileage ran away to. I asked her when she had her filter replaced last and she didn't know, so I checked the filter and replaced it and her mileage went back up again.

I agree spark plugs and wires would be something to replace as well, I would swap that exhaust too. With a 1992 Grand Am I would suggest finding a good deal on an exhaust instead of going aftermarket with it, unless you want to hang on to that car for quite awhile and dont mind the cash.

02-11-2005, 02:28 PM
Air filter
fuel filter
fuel injectors
tranny fluid
spark plugs/plug wires
tire pressure

Get those things changed/looked at if you haven't in a while

Don't floor it
Cold weather gives you crappy milage

02-14-2005, 06:14 AM
i switched the brand of gas i bought.. and it got me a few more miles per gallon... then i switched to Shell V-Power 93 Octane and I get about 370 miles out of a take of gas now instead of about 280-290 .... i have an 00 with v6

02-14-2005, 01:14 PM
Gas mileage... start with the usual suspects:
-dirty fuel filter
-dirty air filter
-driving style (hard acceleration)
-bad plugs/wires

From there you can investigate less obvious candidates:
-exhaust condition (see below)
-MAF sensor is old and out of calibration, consequently engine is running rich

I doubt having a hole in the exhaust is causing any significant problems with mileage... however this brings up some other possibilities being that it was old and rusty enough to rust thru...
1. catalytic convertor - it's old too, and may be clogged up
2. rusted piping - most likely you piping is very rusty on the inside... there will be all kinds of jagged flakes and rough surfaces... not good for exhaust flow. The inside of my 95's pipes look like the surface of mars when I changed it out 2 years ago.

Exhaust replacement... this is gonna depend on your intentions for the car and how much you can spend. IMO, best deal would be to have a shop fab up a new pressure bent (not overly expensive but good flowing) stock size exhaust system. Use a Dynomax muffler, very cheap ($35/piece) and you'll like the louder sound it will keep. The stock stainless dual/dual tips can be cut and re-used.

If you're really hurting for cash, just replace the piping and drivers side muffler, leave the stock passenger side disconnected. To keep the dual system you'll have to get 2 mufflers and the shop will have to install a y-pipe and the additional piping since your stock setup has all pipes running thru the drivers side muffler.

Things I wouldn't waste time/money on...
1. junkyard exhaust replacement... still costs money, will be old and in equally poor condition, will have to be cut and re-welded again anyway, and GT dual is somewhat rare in junkyards.
2. "OEM factory replacement" exhaust - costs more than a shop-made custom performance setup.
3. "premium" gas

02-14-2005, 02:16 PM
i switched the brand of gas i bought.. and it got me a few more miles per gallon... then i switched to Shell V-Power 93 Octane and I get about 370 miles out of a take of gas now instead of about 280-290 .... i have an 00 with v6

What were you using before? If you were using 89 w/ethenol, that would be why. 93 octane won't give you any better gas mileage. The only thing it may have done to improve your mileage is clean your injectors (since the V-power uses mroe detergant).

Also, weather, driving conditions, how you accelerate, etc. play a major role.

It's funny because when it's below zero all week I only get about 260 miles per tank, but when it's 40 degrees+ I get 320 or so a tank. There are many factors to why you may have been getting better mileage. I am willing to bet that it had nothing to do with the 93 octane.

02-14-2005, 02:47 PM
What were you using before? If you were using 89 w/ethenol hummm not sure.. it was octane 87 from different places sunch as Sheetz, Unimart, and Mobile.

02-15-2005, 03:44 AM
I always use 87 octane. At the time I was using Kwik mart gas. I never use ethenol blend... hurts gas mileage.

02-15-2005, 10:35 AM
humm how do you know if it has ethenol or not?

02-15-2005, 12:50 PM
It ususally says. Ethenol lowers the octane by 2 points, so 89 octane w/ethenol will actually be lowered to 87 octane. 87 octane will not have ethenol added to it because the octane would be too low to run a car. I don't know if they add ethenol to 91 or 93 octane either.

02-15-2005, 12:54 PM
humm i seefile:///usr/share/doc/HTML/index.html

02-15-2005, 07:18 PM
when my beretta had awful gas milage turned out there was a hole in the gastank... but i doubt thats the case