I've had my car for more than a month now, and I've noticed that that fuel economy's not up to par with the average. I know that automatics generally use more fuel than manuals, but even so, the mileage should be about 29-36 mpg. I have the previous owner's maintenance records, so I know it's been taken care of before I got it. I don't drive aggressively at all; I cruise at 55 mph in highways and 25 mph on side streets. I've change the oil, the oil filter, and the spark plugs. I've also put fuel system cleaner in there. It's not the high mileage, either; it's still 120,000 when I got it. Not the wheels, either--I checked them before buying, and they're still good. I do have a CAI in the works, so hopefully that'll make it consume less gas. I checked with a mechanic about it, but he said it'll be a hit-and miss affair since fuel economy is determined by a ton of things. What else can I do to restore the fuel economy to what it should be? I'm at my wits' end!

 

Are you running the AC wide open all the time? When was the last time you had it tuned up? Air filter replacement, fuel filter, plugs and wires, cap and rotor, set timing? You might have a fuel leak, it 's not likely but possible. Possible stuck pintle on one or more of your injectors. That mechanic was right, there are about a million possibilities, but check these out and then get back to us.

 

Is your CEL on?


I keep wanting to say its the frist O2 sensor

 

check tire pressure too. it shopuld be pretty close to what it says on the sidewall.

 

umm lets see new spark plugs,cap, rotor, wire, fuel filter, air filter, pcv valve, 02 sensor. also check to see if you have a hole in like your exhaust, i bought a 98 lx 4dr 5 speed gets like 38-40 highway after owning it a week i told the dealer it should be getting at least 38mpg but i was getting 30mpg shifting at 3,000rpm a few days later all of a sudden the cars idle and over all running noise got louder took it in to the dealer he said in the middle of the B pipe there was a hole after that they replaced it for FREE under warranty. i got my 38-40mpg.

check out this awesome site any car it will tell you the gas mileage thats on the sticker when u buy it


http://www.fueleconomy.gov/ hope this helps out

 

OK. First, Thanks for the responses. I'm really trying to get my head around this problem, so having extra heads is a big load off of me.
I only use the A/C if I couldn't stand the heat anymore. I lived in AZ for a while, so the heat doesn't really bother me.
The receipts the seller had from the dealership said they did a 120,000-mile tune-up on the car just 4000 miles before I got it, and they replaced a whole lot of stuff (timing belt, water pump, PS pump belt, alternator belt, compressor belt, spark plugs, among other things). The car was taken for regular oil changes thereafter.
Then, after I got it, I followed sacicons' early advice to another guy by assuming that the guy didn't do any maintenance before they sold the car. I put fuel system cleaner in, and changed the oil w/ both oil and air filters and the spark plugs.
I also change the two front tires to add a bit more traction (and the fact that they were getting separated kinda made me say uncle). I check the air pressure every time I go to get gas, so that's shouldn't be a problem.
No CELs are up, so it's kinda hard to believe it's the O2 sensor. No hole on the exhaust, and I don't hear anything weird in the exhaust note. I did check fueleconomy.gov, but it just confirmed the EPA ratings I got from edmunds.com--29-36 mpg--and that I'm missing out on 5-12 mpg on this car.
Aside from that, I never overload my car. Unless I need it in the car, junk won't be in it. I also clean the car pretty often, so the car never gets heavy enough to affect fuel economy. I know it's a good car, so I never abuse it in any way. You might even say I baby the thing. That's why the low fuel economy is a mystery to me.
Thanks again for the info. I plan on having a diagnostic run on the thing to figure out what's really going on with the mileage, then I'll go from there. Until then, if you guys could give me more ideas on what's causing the drop in fuel economy, just keeping sending them. I'll know if I'm getting ripped off by the mechanic based on what you guys tell me (I've caught a mechanic ripping me by saying I needed to change my master cylinder even after the same exact mechanic changed the master cylinder with a new one earlier). More importantly, I just know somewhere out there, there's a guy who complaining about the same exact thing.

 

OBDII law didn't start until 96. All cars prior were OBDI, and I believe 88 was when OBDI became mandated. So if it were and O2 sensor ther is only one, and that's on the exhaust mainfold/headers

 

Interesting. If it's there's only one O2 sensor--and it gets messed up--then I'll definitely change that myself. But like I said, there's no LED saying anything about it, and I don't want to fix things if they ain't broke--unless those changes give me better performance and mileage.

 

O2 sensors get lazy after awhile, so they dont react fast enough, but arnt always bad enough to set off the light. also, check the ignition timing.

 

I see. I'll try working on the O2 sensor when I have free time; that CAI will have to wait. How easy is it to replace the thing? Do I really need that special tool or can I ghetto the thing out?