Jon89le Posted February 16, 2003 Report Share Posted February 16, 2003 Alright, ive been driving around on 89octane and im only getting a little under 200 miles to a tank. And thats driving her easy and also all highway driving. Now the motor has been modified with cam and everything and has an end compression of about 9.6:1 but i still think this is a bit low. I cant see these mods lowering my miles/tank THAT much. I was reading another threads and most people with 3.1s average 3-400 and those who drive hard all the time averaged a little under 300. I cant even begin to image what would happen if i drove my car hard. Itd be like that old commercial that the guy revs his car(porshe or Ferrari i think) at the gas station after filling her up and the tank goes from full to empty,lol. Would maybe running 93 help? Around here 93 is only 4cents more from damn 89. Would a bad fuel filter cause this? When i did my motor there was a little carbon buildup on the lower intake but not enough that i think itd hurt me this much. Anyone have any ideas? Thanks Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted February 16, 2003 Report Share Posted February 16, 2003 I say try a tank of 93 and see what it does. I had an '89 GP LE 5-speed before and it got about the same as yours on 89. 93 was a little better. I got the best mileage on 87 though. Quote Link to comment Share on other sites More sharing options...
Drache Rott Posted February 18, 2003 Report Share Posted February 18, 2003 did you check your o2 sensor...it can make your gas mileage go bad in a big way Quote Link to comment Share on other sites More sharing options...
Sam96SL Posted February 19, 2003 Report Share Posted February 19, 2003 you neglected to mention if you had ever changed the catalytic converter(s) or not......sometimes this helps overall efficiency....my cutlass(96SL) gets about 21.5 driving back and forth to work....this is a mix of driving...70-80 mph on the freeways and posted speeds in town... Quote Link to comment Share on other sites More sharing options...
Drache Rott Posted February 19, 2003 Report Share Posted February 19, 2003 sam your right ...if his cats are clogged or broken inside they can do more then just lower his efficency...when my cat went bad my gas milage dropped to around 150 miles per tank.... Quote Link to comment Share on other sites More sharing options...
Jon89le Posted February 19, 2003 Author Report Share Posted February 19, 2003 All the sensors on the motor are new. There is a new Catco catalytic converter on there with a new muffler also. Ive been thinking and i think its the thermostat, once i run this tank out im going to run the stock 195º Tstat and see what happens. Right now i have a 160º Tstat which i guess is too cold even for all the mods and temperature outside. Quote Link to comment Share on other sites More sharing options...
godofthunder Posted February 19, 2003 Report Share Posted February 19, 2003 I only get like 250 on a tank, with 89. But i really dont take the hiway that much. My mom with her 91 Lumina with a 3.1 got like 400. Jon Quote Link to comment Share on other sites More sharing options...
toastemcutlass Posted February 19, 2003 Report Share Posted February 19, 2003 so what type of mileage should the 3.4 get the best i ever got was 245 to a tank and that was driving nice and on the high way. any suggestions? is this mileage bad. Quote Link to comment Share on other sites More sharing options...
Drache Rott Posted February 19, 2003 Report Share Posted February 19, 2003 umm the question of gas milage is speculative...need to know the size of your tank compared to the miles...these cars had 3 different size tanks..... 16, 18, and 22. my car originaly had the 18 gallon tank... and I was getting 280 miles=15.5 mpg....I got a hole punched in my tank..replaced it with the 16(it was all I could find in a hurry)also replaced my cat, O2 sensor, and map sensor...miles per tank went to 340 so my miliage went to 21-22 mpg....I think this a damn good on a motor with 170k miles( and my lead foot)..so find out how big a tank you have...but even with the 16 gal tank 250 miles = 15.6 mpg.... you tell me weather this is good or not. Quote Link to comment Share on other sites More sharing options...
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