so i have an 04 cav sedan (auto), with 35,000 miles, and about 4,000 miles on the oil (new filter to) that is all synthetic. about 3000 miles ago i added, a k&n drop in filter and removed the airbong, everything other than that is stock. My tires just got aligned and rebalanced, yet my mileage still sucks. I drive about 100 miles a day to work, in where i cruise around 55-65 mph, with just about 14 miles total city driving. I have filled up with 87 and 91 octane gas, and i still get the same mileage. I dont jack rabbit the car (geting up to 4th gear i never go about 2.5k rpm), and i get about 28mpg, why is this so crappy?? any help would be greatly appreciated!!

It's an automatic. That is decent gas mileage.


My Car

i wish i got 28/mpg, live in my land of 17-20/mpg might want to check o2 senors i had one go crappy once on a beretta i had and my gas milage dropped to the floor.


Mike Jones..... Who?

A little more info might help. How hot is it where you live? Do you run the A/C alot? Is it flat land or hilly? All these play a factor in gas mileage. I have a 98 Z24 and get 30mpg going back and forth to work. I drive about 40 miles round trip a day. When I use the car for some city driving, my mileage drops to around 28.


98 Z24

RIP Specks

i never use AC allways keep all four windeows up, i always have just plain HVAC on high though (does that effect anything) the land has some sharp hills (like maybe 5% grade) and the rest is dead flat. WHere i live its about 65 degrees average (coast).

Have you had the injectors cleaned? I usually drop some Fuel Injector Cleaner in the gas tank about every 3000 miles. Hills will affect gas mileage. Do you have your tires properly inflated? Are you using stock size tires or have you changed them? I'm asking all the questions to help ya out.


98 Z24

RIP Specks

my tires are all inflated to the right size, and they are the stock tire size. for about 1000 miles i was running chevron 91 octane with techrno (this was maybe 2000 miles ago) so i thought that would clean them out. any other ideas

I only get 28 mpg if I measure it using those bigger British gallons.

Actually, I've got up to around 28/29 mpg on the rare occasion that I do ALL highway driving, but my average mileage is 24.1 mpg right now (in your US gallons).

Sounds to me like you're getting exactly what you should be.

kinda dissapointing though since epa is around 33 highway............

Yeah, but they come up with those numbers in a lab based in their own little fantasy world.

mine gets better milage at 75-80 then it does at 55-60


there was a thing in the news recently that the EPA ratings are screwed up cause the do not accuratly do their testing as to the way the cars are used now adays , they are using older testing methods


also keep the tires inflated to a higher than sticker says on the door , i keep mine at a minimum of 35psi to 40 psi

your better on over inflated than under inflated

I get 33 mpg highway with my 02 2.4L. If I do a straight run with no city driving I can get 34+. But I always go the speed limit.

Oh, and I have an automatic transmission.

I think your bad mileage on the highway might be because of the K&N air filter and bong removed (this helps if you take it easy on the gas), but the EPA results are done with the bong and stock air filter in. So that could be messing with the results.

Another thing you can do is get some fuel injector cleaner

The epa testing is always off because it's all done in a lab. Honda's 50 mpg hybrid civic got 26 in a test I just saw in the paper and the dodge half ton and durango were getting 8 when they said 15.

I just went on a gas mileage kick in my 02 ecotec 5 speed. Removed the bong, put in K&N filter cleaned the throttle body and IAT sensor, replaced the fuel filter, changed oil with 5W30 synthetic, ran a bottle of techron through it, added a small amount of acetone, covered my grill with cardboard, removed my passenger side mirror, antenae and windshield wipers.

I drive as stated, no jackrabbit starts, shift around 2500RPMs, and follow the speed limit. I just got 37 mpg flat freeway/highway 65-75mph. Then I got 45 without running the ac going 70 mph with a small part of it downhill. I know I can get more than this when I mess with the aerodynamics more.

BTW covering the grill caused it to run slightly warmer at speed with no change in temp at low speeds. I imagine the added heat causes the gas to burn more completely.

Hope this helps.

Average of 35mpg with a 04 ECOTEC bone stock base line cavi with the 5 speed. This is in Arizona with going over top a mountain every day. Up and over to goto town and up and over comeing back. Its nice comeing back since I don't use the gas coming down the mountain.

Somebody should design a front cowling for our Cavaliers like the old Dodge Charger Daytona’s. That would be cool!

You guys suck. Driving like a grandpa I got 25. Normal is 20-22. I need a new air filter though.........


1971 camaro 427 --- here!

Stock... and loving every minute of it.

Run some injector cleaner through the system. Inflat your tires to 32psi. DO NOT inflat the 205/55R16 to 30. That air pressure is too low. I run my Eagle GT II at 32psi and as I stated with A/C running on a highway trip, I get 32.5mpg. Going back and forth to work, I get 30mpg since there is some city driving in there.
As far as EPA, they do the testing in doors. No wind resistance. I have always gotten close to EPA mileage on all my new cars. Just depends on how you break them in. Since highway speeds are normally around 65, that is where I break mine in at. When on a trip I usually do between 70 and 80 since the speed limit ranges from 65 to 75.
Your bad mileage is NOT because you removed the intake bong and run a K&N filter. I did the same thing and saw no drop in MPG or HP. If anything it should have helped with MPG since you now have a less restrictive air flow. I still say try the fuel injector cleaner.


98 Z24

RIP Specks

With about 80% freeway at 70mph I'm getting about 30 MPG with my 5 speed 05 sunfire, so 28 for an auto sounds about right to me

Did your car always get this kind of mileage or did it just start doing poorly? My 04 Sunfire GT with auto was rated at 43 mpg / 6.6 L /100 km. and 29 mpg / 9.8 L/100 km. city. I use 94 octane because I have a vortech supercharger on my engine even with that I,ve never had less than 32 mpg on the highway and if I keep my foot out of it I get 40+ mpg driving at 100-110 kph/60-70 mph. I know our gallon is bigger but even so you should be doing better than that.


Thats Him Officer The WICKED One.

chris orr wrote:Did your car always get this kind of mileage or did it just start doing poorly? My 04 Sunfire GT with auto was rated at 43 mpg / 6.6 L /100 km. and 29 mpg / 9.8 L/100 km. city. I use 94 octane because I have a vortech supercharger on my engine even with that I,ve never had less than 32 mpg on the highway and if I keep my foot out of it I get 40+ mpg driving at 100-110 kph/60-70 mph. I know our gallon is bigger but even so you should be doing better than that.

Note that those MPG ratings on the Canadian cars use BRITISH gallons and are not the same as those used in the states. I think it's a scam. They only do it because people are accustomed to hearing MPG values from US advertising and they figure they can make them look better by using British gallons or something.

That 43 mpg is a little less than 36 mpg on the US scale.

well the thing is, before iw as getting close to around 37, then all of a sudden the rapid drop. My tires say 35 psi, so well before long trips (300 miles all highway) i make sure its at 35, but i still get around 28 mpg. wtf man!

I had the same problem. I ran injector cleaner through the engine(fuel additive), changed the oil to 5W30 synthetic, changed the fuel filter(TRY THIS), and then sprayed carb cleaner in the throttle body and the IAT sensor in the intake tube, and LAST but NOT LEAST cleaned my K&N filter. I am running 45 psi in my tires. Went from 24 mpg town 29mpg freeway to over 30mpg around town 37-45mpg highway

Biggest things are probably fuel and air filter