Topic: Pontiac Grand Prix 1998, 3.8 L - fuel consumption

[ssagar78]

Hi Everyone, I am new here so I would appreciate any information you can provide.  I have a 1998 Pontiac Grand Prix GT, 3.8L and I have been trying to get my fuel consumption down to 13.5L/100 km and below.  I first bought the car in 2003 and the fuel economy was consistently at 13.5L.  I have an indicator on the car that lets me know what kind of fuel economy I am getting.  Recently I have been noticing over the past year that it has risen and stayed around 15.5/16L for every 100km. 

I use GM spark plugs, use the good oil for high mileage vehicles (194000kms) Castrol, cleaned out the fuel injectors, replace the air filters (checked regularly Fram), oil filter (fram).  I try and stay between 1 and 2 RPM and stay at 60km.  I use regular gasoline primarily from Petro Canada.  Is their anything that I am missing that should be checked. 

Thanks,

[articsteve]

Recently I have been noticing over the past year that it has risen and stayed around 15.5/16L for every 100km

Don,t rely on that device.  You may be getting better mileage than what it says.  The only method is to record odo reading and compare to info from gas receipts.

[kevlar]

i say sell your car and buy a honda fit.  you will save the price of the car in gas and repairs.

[Baron von Raschke]

Hi Everyone, I am new here so I would appreciate any information you can provide.  I have a 1998 Pontiac Grand Prix GT, 3.8L and I have been trying to get my fuel consumption down to 13.5L/100 km and below.  I first bought the car in 2003 and the fuel economy was consistently at 13.5L.  I have an indicator on the car that lets me know what kind of fuel economy I am getting.  Recently I have been noticing over the past year that it has risen and stayed around 15.5/16L for every 100km. 

I use GM spark plugs, use the good oil for high mileage vehicles (194000kms) Castrol, cleaned out the fuel injectors, replace the air filters (checked regularly Fram), oil filter (fram).  I try and stay between 1 and 2 RPM and stay at 60km.  I use regular gasoline primarily from Petro Canada.  Is their anything that I am missing that should be checked. 

Thanks,

Hmmmm....I have a 2000 Grand Prix GTP and I'm averaging 10.8 with mixed driving. Aside from the supercharger, which would make mine a bit thirstier, the only other thing I use is a K&N air filter.  I also change my fuel filter whenever recommended by the mechanic, but not sure that would make that much of a difference.  If you're doing a lot stop and go driving your consumption would increase.  I was averaging about 13.0 when I lived in Toronto. 

[Zoo]

Have you ever had your compression tested? I wonder if the piston rings are starting to get more worn and you are getting some blow by. I wonder if your valve seals are suffering from the same fate.

This could partially account for higher fuel consumption.

[Honda Owner]

The car is old and getting worn out. It is simply not worth spending money on. If you are interested in cutting your gasoline bill, a new car that gets 8.0/100km would pay for itself pretty fast.

[Car_nut]

It is not unusual for older car to have worse fuel economy. My 1996 Plymouth Voyager with 3L V6 was getting 13L/100km when new and decline to about 15L/100km for 100% city driving for the past few years. I did change spark plug and air filter every 2 years, oil change every 3 months.

I guess as the car aged, mileage get worse. I doubt you can get significant improvement on gas mileage for such an old car. If it is still reliable, keep it, gas probably cost less than a new car payment.

If you drive a lot, then may be look into a newer compact car with better mileage.

[maritime_storm]

Couple things I noted. you didn't mention changing your fuel filter or O2 sensors, both of which can account for fuel mileage increses. Tire pressure, extra weight carried in the car, type of driving done, ambient temperature of operation all make a difference.

[barrie1]

You have a very fine car with a great engine design which should not be worn out with this low milage at all. Some import brands I would suspect that of but not a 3.8. The only way I would suspect your engine to be getting tired would be if you are not good on changing your oil. The gauge on your dashboard is basically a vacumn gauge and its possible some of the rubber hoses under the hood are getting cracked and tired which will make them leak giving false readings.