What sort of gas mileage on GM 3.1 or 3.8

[va3ux]

I'm *thinking* about a Grand Prix to replace my aging Intrepid next year (if I don't get another Intrepid or perhaps a 300M).

What sort of gas mileage are you getting on the GM 3.1 and 3.8's ?

Thanks...Phil

 

[Clyde65]

Well my Buick with the 3800 averages 19.6mpg between city and highway driving. That at least is what the computer says. I haven't driven it on a long highway trip yet to get a straight highway figure, but I suspect it to be somewhere between 26mpg and 29mpg. I wouldn't recommend the 3100, especially since the 3800's are readily available in the Grand Prix. Also, depending on how tall you are, the Grand Prix might be a little tight. I have heard that the 300M is very roomy.

 

[dwendt44]

2005 Grand Prix GT 3.8.
Mostly hyway miles, (85%), now broken-in.
Mobil-10W-30, getting in the low 30s.
Best mileage was 38, but that was two lane, fill up and go, 55 mph,20+ mile trip.
often in the 32-34 mpg range. Summers, of course.
This by the DIC computer.

Edited to add: the 3.1 would not do better, IMHO, it works harder moving this heavy car.
EPA ratings are very close and the extra power, what there is of it, is needed.

 

[Matt_S]

2000 Monte Carlo 3.8.

I get 24 in rush hour commuting involving a fair amount of stop and go. On highway trips, 29 - 30 if I average 70 mph, 27 - 28 if I push it higher. I've seen up to 36 on a highway trip where I had the wind at my back.

I'd also definitely recommend the 3.8 over the 3.1. It'll get you 30 more HP and a lot more torque with very little penalty in gas mileage.

 

[eljefino]

Had a 99 Olds Intrigue (same as grand prix) 3.8: 25 MPG driving around town, 30 with the cruise at 65. My Saturns get the same in town or on the highway so I figure the weight of the Intrigue holds it back.

Car was well put together, 197k miles and still felt like an almost new rental.

 

[Matt_S]

The 3.8's have had some intake manifold gasket leaks. The newer ones have a redesigned gasket and fasteners that should solve the problem. Dexcool has never REALLY been a problem, but it will turn muddy if the coolant level is constantly left too low in conjuction with the manifold leak. The coolant issues are more of a symptom than a problem in their own right. If you're buying used, which it sounds like you are, make sure the car has had any recalls attended to and that the coolant is a nice clear orange color with no muddy deposits on the radiator cap. If you're buying new, you have no worries with the 3800.

 

[dwendt44]

Get the GT; more goodies and it will be worth more at trade-in. The 3.8 is/was standard in the GT. Only option I didn't get was the sunroof, which I don't care for and the supercharger which requires(or it did)premium fuel. I don't do high test. It's a rip-off.

 

[Pat M.]

My 94 buick century(3100) gets 24mpg...80% highway.


My dad's 99 park ave(3800) gets 22mpg as per the computer...40% highway.

 

[tsmay51]

My wifes 2000 malibu gets about 24mpg in the city and about 32-34 on the highway. That is the 3.1 or 3100 motor.

 

[Shaman]

My 97 GTP would get about 22-24 on the street, and between 30 to 34 on the highway. It was the car after my Honda that got 27-29 on the highway.
If you are looking for used, go with a 98 up GT or GTP. The GTP will have lower numerical gears, but you should run premium in it because of the SC. I used to pull the belt on highway trip and run 87 without a problem, confirmed by a scan. It has knock sensors that will pull timing, and it doesn’t have a faulty Intake manifold to worry about.

I would recommend a Grand Prix. It is the only car I have owned that I would own again.

 

[Clyde65]

quote:

---

Originally posted by Shaman:
I used to pull the belt on highway trip and run 87 without a problem, confirmed by a scan.

---

Are you saying that you unhooked the drive belt to the supercharger and were able to run it that way? You're kidding me right?

 

[va3ux]

What's the difference between the GT and GTP ?

Are there any other general problems that these cars are known for ?

Thanks again folks. I really appreciate all the info.

Phil (2001 Intrepid 2.7 V6 w/ 249,000 km 0r 154K miles)

 

[dwendt44]

No serious problems.
The 97-03 are a little more driver friendly.
The new series 04 and up, are pretty trouble free as well.
The GTP(supercharged) require premium fuel; the 05-07 models can run regular with some loss of performance.
the 01 was re-called for warped intake manifold,(brittle bolts), only real problem I've heard of.
Some of the used GTPs may have been hopped up, and driven hard, if your looking at used.

 

[JavaMan]

We've have a 1999 and had a 1995 Buick Lesabre. They've both been between 34-36 on the road. City driving hasn't been shabby either. While I never think to check the mileage around town, we don't have to fill up very often.

 

[va3ux]

Thank-you-Gents !

You've all given exactly what I was looking for.

Looks like the 3.8 is the way to go, and gas mileage is right around the same (or a bit better) as my Chrysler/Dodge 2.7 V6 in the Intrepid.

I really like Intrepids; been driving them 12 or 13 years. But I had a Grand Pricks as a rental twice recently and I really liked it too.

Thanks again everyone.

Before I go....any bad stuff with the 3.8 ? Is this the one with the coolant leak at the intake manifold gasket and the issue with Dexcool ?

Phil

 

[va3ux]

I'm impressed with the gas mileage figures you guys are reporting. I was not expecting numbers this good. I get mid 20's city and a solid 30-31 mpg Hwy with my 2.7 in the Intrepid. I didn't think I would be able to see that kind of mileage with any other mid sized car but it looks like I'm wrong.

Thanks again guys.

Phil

 

[va3ux]

Another "bonus" with getting away from the Chrysler 2.7 (if you want to call it a Bonus) is that I would no longer have to worry about breaking one of the 3 timing chains ( a frequent cause of destroyed 2.7's), or worry about high temp sludge which also leads to lubrication related failure of the engine. The 2.7 runs hotter than most engines and cooks oil on the heads.

 

[ATS-V]

In my 97 GTP I average ~22mpg commuting. On a all highway trip I can get 29mpg. I have 130k and the car runs as good as the day I bought it. I would get the GTP over a GT, the torque added by the supercharger surpasses some V8's. You can also mod the L67 quite cheaply.

 

[dwendt44]

The Grand Prix can now be had with the 5.3 liter V-8(aluminum block). Lose a couple of MPG, but gain a big grin factor.

 

[Racerjk]

We just averaged 29 MPG in my wife's GTP driving 77 to 78 mph. The car was fully loaded down and the a/c was blowing cold.

We've gotten as high as 33 mpg driving between 70 and 75. In town driving is another story though!