So my usual mpg for city driving is around 19.5 (more or less) and around 21.5 on the highway. I went on a little road trip to jersey from NYC last week and filled up in with 93 Octane at a Shell station in new brunswick. Over the next few days, I began to notice my gas mileage return to its normal 19.5 or so and then some. Now, for the past five days, my gas MPG has been decreasing by at least 0.1 daily! I figured it was probably the gas quality that I bought out in New Jersey. I then went back to my BP(Amaco) spot and filled up, hoping that my MPG would return to normal. Instead, it continues to decline.. Now I am at 17.8 MPG and still going down daily. I spoke to a friend of mine who is a mechanic and he says that I may need to change my fuel filter. He also suggested that the bad gas from Jersey may be a cause of the problem and that some remains of that gas may still be in my last tankfull.. so I should burn this current tank out again and full up and then see if I notice any positive effects. If not, then change the fuel filter.

..any other suggestions on how to get my 19.5 city MPG back?

 

6 speed or automatic? I know how you feel. I have a 6mt and my gas mileage is 18.5...but Im getting new spark plugs so hopefully that will do the trick!

 

Auto.. I just changed my spark plugs in may with NGK platinum.. so I dont think thats it.

 

Try some fuel injector cleaner, could be dirty injectors. I just started noticing bad gas mileage on mine not long ago, ordered some injector cleaner, hopefully that'll clear things up. Another cause for bad gas mileage is the winter grade of gas???

 

Try a Seafoam treatment.

 

Whats a good fuel injector treatment to use?
I've never done the seafoam.. do they sell it at say an Autozone?

..Any other suggestions on how to correct this?

 

Are you measuring MPG using the trip computer or by using a proper method of calculation?

 

I'm reading the trip computer.. it may not be as accurate as the proper MPG method.. but it is an accurate indicator in showing that I am losing gas-burning efficiency


..any suggestions puppet?

 

You can buy Seafoam at the big 3: PepBoys, AZ or Advance. Try anything with Techron.

I get 20 mpg around town and 30 mpg on the highway.

 

How are you certain it is accurate?

To be honest, I doubt the trip computer's ability to do even that. But maybe my trip computer is completely busted. I would still do MPG comparisons using how many miles driven divided by how many gallons used.

There are also many other factors like tire pressure, driving conditions, etc...

 

That much? I barealy can get 350 highway miles out of a full tank (16 gal) and thats about 21 mpg...

Something is wrong here....

 

You're right, something is wrong with your car. Quite a few people can get between 27-30 mpg on the highway. If I keep it under 80 and use the cruise whenever possible, I can get around 30. Some folks have even claimed 500 miles on 1 tank of gas. Now that's pushing it. What can I say, every car is different.

 

let me do the calc...

30 mpg x 16 gal = 480 Miles



I dont get it... car runs strong and I actually drive slower than my grandma... And I just changed plugs (twice actually), air filter, and i'll be changing fuel filter soon...



What the hecka is going on?!!?

 

I've gotten 440 miles on a tank... but remember, some of us 02-03s have the 6MT. 6th gear helps big time if you're just cruising on the freeway.

 

Are you going by the trip computer? The most I've ever got was 28 mpg and that was doing no more than 65 the whole trip. My trip computer read 32 but it's well know that those are inaccurate and always high. So if you are going by your trip computer your probably getting 26 or 27 hwy. If not then you may hold the record for 5.5 gens. Do you have a 6 speed?

 

To all the people in this thread wondering about their declining gas mileage, please take into account the modified winter fuel mixture that gas stations now use since it's getting cold. It will decrease your mileage.

 

19mpg is actually pretty good in the city....i'm only getting 16-17 in the city, with short trips...even if i granny it...you just can't get around the 3.5L displacement with constant stop and go...no matter the gearing!