Bad gas mileage

[captain nismo]

Well just recently my 1989 240sx with a 5-speed transmission started to get bad gas mileage. I just filled up, and after a little math i figured my mileage to be 16.76mpg. Is this bad? I only got 310km in 43.5 litres, when before i would have been over 400. I replaced my o2 sensor when i first noticed this, but i dont think there has been any change. My car has 164,xxxkm on it. Any ideas of what to check next?Chris

[CanadianCoch]

that isn't great, I average around 22. Check your fuel filter, clean your injectors, make sure they aren't leaking, replace your spark plugs, your air filter, if it's an s13 check the AIV, check your timing, your wires, thats all off the top of my head.

Dr.

[iamaprofessional]

if it still sux after that...or before, buy a gallon of Toluene. You can find it in the paint thinner section of your local hardware store for somewhere around $15 CAD. At your next fill-up put 1/3 to 1/2 of the gallon in your tank before you fill it. Do this a couple times (maybe even with a couple gallons) This did wonders to my gas milage! It will clean EVERYTHING out it will also boost your octane a lot more than some $12 octane booster that is a fraction of the size.

You WILL want to change your fuel filter after you run it all through tho, it will be FULL of gunk.