gas millage on 2004 Pontiac Grand Prix ?

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I have this 2004 grand prix since 08. I have never been impressed with the millage on the highway. It has always been around 23-25 and that is running around 77-80mph. I really like the power it makes.

In the city it seems that with my wife driving it we maybee get 250 out of a tank ?

It has 90k on it, i run AMSOIL 0w30 SSO with a drop in K&N

any ideas would help ?

thanks,

Steve
 
I have a 2007 Grand Prix. I get 25 driving to and from work-10 mile mix of highway & city. I usually get 30 on the highway running at 60-65 mph. Here my tips:

run tires at 35 psi vs the factory stock of 30 psi. Make sure your alignment is correct. GP's are notorious for the rear being way out of alignment. Most of all it sounds like your driving habits are causing low mileage. "Like the power it makes" probably means you are heavy on the gas pedal. Don't take this personally, but you have to use the gas like there is an egg shell between your foot and the pedal. 77-80 mph is never going to get good mileage. Slow down or live with the poor mileage. Women usually get lower mileage. They seem to "race" to the next red light and they are pretty heavy on the pedal. Quick starts and last minute stops kill your city mileage.

Just my two cents,

dave
 
If you 25 aronnd town & 30 on the hwy. You have nothing to complain about. Down sizing will increase your mpg.
 
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Originally Posted By: willix
If you 25 aronnd town & 30 on the hwy. You have nothing to complain about. Down sizing will increase your mpg.


Agreed. If you want better mpg slow down. 25mpg @ 80 mph is awesome.
 
Grand Prix's aren't known for good gas mileage. They're tuned and geared pretty aggressively for a "sporty" big car. 25 mpg going 80 is a lot better than some folks! Some other GP owners get that at 60 mph.

If you want a car built on the same platform with better gas mileage, find a young guy with a Buick Regal. They're not as aggressively geared/tuned as a GP.
 
Originally Posted By: sciphi
Grand Prix's aren't known for good gas mileage. They're tuned and geared pretty aggressively for a "sporty" big car. 25 mpg going 80 is a lot better than some folks! Some other GP owners get that at 60 mph.


Can't speak for other models, but my grand prix is geared very tall. Turns 1500rpm at 60mph. Gets better mileage than the ford contour it replaced.
 
I have had an 01 GTP and now the 98 Regal GS, both supercharged.
They get almost identical mileage and the tune just isn't enough to make a difference they ran almost identical 1/4 mile times. I just went on a 600 mile round trip from north of Seattle to Albany Oregon in the Buick. I averaged right around 65 to 70 mph on the higway and pulled down right at 29 mpg average for the trip.
I had a 98 N/A Bonneville that with even 240,000 miles on it would pull down 28 mpg going 65-70 mph on the highway.
 
Depends on what ratios are in the transmission. My Buick LeSabre with 2.86 gears turns ~1500 RPM at 60. Others with 3.06 gears turn ~1800 RPM at that speed, IIRC. The gearing will have an effect on fuel economy.

Also, when was the last time it was tuned up? The 3800 in my Buick had a noticeable improvement in power and fuel economy when replacing the plugs and wires.
 
A clean air filter, synthetic oil, an oversized filter and high pressure in the tires are about all you can do.
36-39 lbs. in the tires will help.
No junk in the trunk.
There is a 'sweet spot' for mileage on most vehicles. My 05 GP got over 30 at highway speeds-hit 35 a few times under ideal conditions.
Drive easy. Slow down a bit.
 
I LOVE THE INPUT, I heard a rubbing of a brake in the rear. My buddy did them back in September. I have to have it looked at. Also, I do need to clean that K&N it has been a year.

I just had new NGK plugs put in but no wires.

Can anyone give me some advice on good wires?

I use to love JACOBS but they are no more.

I do run the tires at 35-40psi.
 
With a diver and passenger, that vehicle is 2 tons.

I'm not a speed Nazi, but if you slow down on the highway you will make the gas mileage jump. You can get 3-4 more that way.
 
OK, everyone stop for a moment. I too owned this car, albeit under Buick clothing, mine a supercharged Regal GS. I got similar mpgs with the GS.

Before we go any further, which engine is installed in your GP? These GPs have come with three different, distinct engines -- the 60 degree 3.1L (the one known for the lower intake leak issues), the normally-aspirated 90 deg 3.8L V-6, and that engine's supercharged 3.8L relative.

I would fully expect different mpg outcomes with each different engine. Please elaborate on your drivetrain (or please tell me where I missed this info...). Thanks.
 
I really never saw a huge difference between my N/A Bonneville and my Regal GS. Both 3800 cars. The Bonney always got a little, might be due to the fact that is was about 250 lbs heavier when weigh on the scales.

He states his in an 04. The 3100 was dropped for that year, the base model car had a N/A 3800.
 
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