Help! Gas mileage just went from 30mpg to 17mpg!


I have a 98 Acura and just had a full service. The car is running better then ever but the first tank after the service I got 20mpg - I always get 27-30mpg - and this last tank yesterday I got 17mpg. I took it in to the mechanic this morning and he found nothing wrong and said it had to only be the gas I was using!

I set my trip odometer at 0 when I fill the tank and then check the amount at the pump- i usually fill when empty=10 gals.

I thought maybe my trip odometer was running slow, but I wrote down the actual mileage and I drove 140 miles round trip yesterday and had filled up when I left. I re-filled (not completely empty) and the tank took 8 gals. That is 8 gals for 140 miles!!!

I can’t keep this up I will go broke : (


he found nothing wrong and said it had to only be the gas I was using!

That’s BS. While there are times, like winter, when the gas can cause a reduced mileage as they use a different less powerful mix in winter, they are not doing it now and it does not make that much of a difference.

Was that the dealer, a chain outfit or an independent that did the work?


he’s independant and usually very good - my friend said it could be a faulty oxygen sensor

i guess i was wondering if thiscould have been caused by something the shop did because it happened immediately after i got it back from them


Do you have a check engine light?

What was included in the “full service”. Full service can mean a lot of things, look at your receipt and list all the things on it, it may give us a clue.


Someone may have “borrowed” your gasoline.


One possibility. Make sure your temperature gauge is staying at the specified level. If your engine temp. is slightly above or below normal, it can kill your gas mileage. Could be a faulty thermostat or sensor, a relatively easy fix.


Does the car appear to be running as well as it did before and does it idle smooth?

I would think a gas mileage drop this severe (if real) would show some symptoms such as a CEL illuminated, slightly rough idle, black smoke out the tailpipe, and slightly sluggish running.

Who performed this service? Since the vehicle is distributor equipped I wonder about the possibility of someone altering, incorrectly, the ignition timing. Retarded timing could easily cause this problem if someone failed to use the test plug when checking and setting the timing.