Hey guys.i did a trip readin in my 99 si and turns out that my tank gets approximately 200 mi on a tank (city miles).the fuel gauge fluctuates within 3 bars either going up or down.i was told by the previous owner that the check engine light was on because of a o2 sensor.would an o2 sensor effect gas milage that much?? 200 seems pretty low..makes me feel like im driving a V6.any other possible ideas?
horrible gas mileage?
- Thread starter Milano_SI
- Start date
could be just the simple fact that its city mileage not highway mileage. still seems a little low though, check to make sure tires are inflated, the simple things like that
200 is pretty damn low. i get 330-350 on a boosted 1.8. sounds like yours needs a tune up. which o2 sensor is bad? the downstream o2 sensor does not effect your engines performance at all, only the upstream
200 miles on how many gallons? 200 miles on a "tank" doesn't tell much since you could never run it bone dry.
So are you running the tank dry?
Because according to you you're getting 18 miles per gallon. That's V8 gas mileage for sports cars. You'd have to be throwing a lot of codes in the rare event that happened. Driving this car would be uncomfortable and the car would probably be bogging.
Here's what I want you to do (just want to make sure you're really doing it right).
Reset your tripometer each time you gas up.
Gas your car up and get a receipt.
Write down the miles recorded on your tripometer on the receipt.
Now look on the receipt for how much gas you just pumped in.
For example, say the other day I gassed my car up. I gassed it up far before the tank was empty, but I can still tell exactly what my gas mileage is, even without looking at the gas meter.
So I drove 188.9 miles (from tripometer).
I put in 5.179 gallons of gas.
So 188.9 (miles driven) divided by 5.179 (gallons put in tank) equals 36.47 (mpg).
So (miles driven) divided by (gallons put in tank) equals (mpg).
So 36.47 is my miles per gallon.
The tank capacity means NOTHING unless you ran the tank totally dry.
i'm surprised you're not throwing codes. you'd be throwing a code if your O2 sensor was faulty. I wouldn't recommend driving that low on the gas tank either. How do you drive?
i'm surprised you're not throwing codes. you'd be throwing a code if your O2 sensor was faulty. I wouldn't recommend driving that low on the gas tank either. How do you drive?
yeah.it has a CEL like i said before.previous owner said it was the o2 sensor.i need to scan the codes to actually see if theres somethin more needed.besides that the motor runs fine.
i'm surprised you're not throwing codes. you'd be throwing a code if your O2 sensor was faulty. I wouldn't recommend driving that low on the gas tank either. How do you drive?
No, not dry.just til the E because i wanted to see how much the trip read.
maybe its just your mods and/or driving style. i only get 20mpg in the city but 42 on the highway. in the winter its way lower tho. summer means warm air with less O2 so the ecu dumps less fuel in and you get better mileage 
try to drive shifting below or at 3k rpms if possible. this helps a ton.
try to drive shifting below or at 3k rpms if possible. this helps a ton.i been kinda in the same situation. Last fill up I only got like 20.1mpg ( i always calculate my mpg each time I fill up) normally im around 23-24 city, and 30 highway, but this time I didnt even hit 200 on the trip, I used to get 250-300 when I was in florida driving on base. Same mods in both states, Intake and catback, with no CEL's. It boogles my mind, replaced the air filter, replaced the oil, replaced spark plugs and I still cant figure out what it is! Sorry, didnt mean to thread jack
Is that really to 11 gallons though? That's beyond E.
18mpg is REALLY low though.
Autozone and other parts stores will read codes for free on '96 up (OBDII) vehicles. They'll also print out a little slip saying what the most common causes for those CELs are.
Do you guys think my gas mileage sounds bad?
Mods: SMSP 4 - 1 with 2.25" collector, 2.25" high flow cat, and 2.25" magnaflow piping with oval muffler.
From Full to pretty much almost empty I'm getting like around 350 - 380 miles to a tank. It's really all highway mileage, with very little city. Sound about right? I have a CEL from a crank positioning sensor, but I don't think that would affect too much. You guys think a tune up is in store? Motor currently has around 130k.
Mods: SMSP 4 - 1 with 2.25" collector, 2.25" high flow cat, and 2.25" magnaflow piping with oval muffler.
From Full to pretty much almost empty I'm getting like around 350 - 380 miles to a tank. It's really all highway mileage, with very little city. Sound about right? I have a CEL from a crank positioning sensor, but I don't think that would affect too much. You guys think a tune up is in store? Motor currently has around 130k.
Figure out EXACTLY what your gas mileage is, not just about where your odometer is when you fill up normally.
Lets say you do do what you said, how do I know I used 5.179 gallons of gas?? I mean I could put 5.18 gallons of gas, drive around and USE 6 gallons of gas from gas that was already in there. Wouldn't that throw off the gas measuring too???
I think I dropped to 24mpg. Time to change my oil, I think im at the 3000mile mark.
I always fill up the tank all the way and then reset the tripometer.
Then I can wait and fill up with 10 gallons or with only three gallons. It doesn't matter.
The pump at the station and the receipt will both tell me exactly how much I just put in my tank, then I write down how many miles I've traveled since I last filled up and reset the tripometer.
So I could fill up and reset my tripometer.
Then the next time I'll fill up when I'm around half a tank. I put in 5 gallons of gas so the tank is now full. I reset the tripometer. I write down my mileage on my receipt so when I get home I have everything I need to do the math (gallons used and miles traveled).
So XXX miles divided by 5 gallons equals my miles per gallon.
The next time I run almost dry. I put in 10 gallons of gas so the tank is full once again. I reset the tripometer again. I can still tell what my gas mileage was on this tank by taking the miles traveled and dividing by how many gallons I used.
So XXX miles divided by 10 gallons equals my miles per gallon.
Or you could just record it all on GasSavers.org and it will do the math for you.