General Motors 3800 V6 gets good mileage?

A few years ago, I read an article in Motor Trend about a man who drove a 1989 Buick LeSabre that got 30 mpg! All he had to do was drive it.

My mother in law had a 1988 Chevy Monte Carlo with the 3800 V6 and she said her mileage was also 30 mpg. So that got me thinking, why aren't people on these forums discussing these engines/cars?

When my Lebaron's tranny went (may it rest in peace), I bought a 1995 Oldsmobile 88 with the Series II 3800 V6. This car is huge! My family of five can fit in it comfortably.
The car only had 73,000 miles on it and it looks brand new!! It has a 4 speed tranny with lockup torque converter. It floats down the highway as it takes me to work. (25 miles each way) All I have to do is set the cruise, turn on the a/c (I live in Texas, a/c is a must) and float my way to work. All the time getting.......... 33 miles per gallon!!!

This car has no mods except acetone in the gas.

I get a real kick out of some of the other gas saving sites with their Honda lovers bragging about the little soda cans, I mean Civics, getting 31 Mpg. What is the deal here?

If an American car can get such good mileage and delivery some luxury too, then why aren't we shouting it from the rooftops?

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Comments

General Motors 3800 V6 gets good mileage?

Pinhead's picture

You know what, I completely agree!!! Every single mid-to-full size GM car with a 3.8 has gotten ~30mpg. They've got excellent power, last forever, and get great mileage. IDK why we aren't crazy for them. It's probably because they're usually put in "grandma cars" that don't have the subconscious appeal and therefore get overlooked.

If I was driving an S10 instead of a Ranger I'd consider trying to get a 3800 to put in it. They run so good and get such good mileage, I'd love to see one with grooves, lynz, & ringz in it.

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General Motors 3800 V6 gets good mileage?

Al's picture

The 3800 is also a bullet proof motor. One of the best engines out there for reliability.

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General Motors 3800 V6 gets good mileage?

BMac's picture

I agree! My V8 Dakota is starting to show me some gains on the hwy in the mid 20's. I saw 24 - 26mpg but it was a hellish windy day and netted 22 one way and 20 the other. I just put a new tranny in it now I have a pinion bearing going out in the diff. Another $300+ to throw at it.

I advanced the cam, put Halo's in it, Amsoil and built me an Aero Cap! When the hwy mph surpasses the Soobie's, I'm taking it on vacation!

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General Motors 3800 V6 gets good mileage?

E=mc2's picture

a quote....

"Another real small project evolved around finding a vehicle that
would qualify as 'almost full size' and still achive mileage
comparable to the majority of the small cars now sold. We knew that
the 3.1 GM engine had a good record and tryed a few 4drs to suit our
needs. We settled on the Century, a nice 2000 model with mostly
standard equipment and maintenance. This vehicle is normally rated
at 31MPG Hiway from the factory. Prior to mod, average hiway was 28
MPG.

We changed the oil to 5W30.

Added 4 oz of energy release.

Reset the computer.

New tires, proper size.

Installed two Neo magnets on the fuel line. 1/4 x 3/4 South Pole
facing line.

It took about 200 miles of hiway driving to get a
good result from these mods.

Now getting a little over 36 on hiway.

We wanted to install the Neos before we added the Acetone/Colemans,
which is next.

I feel that just about anyone can get small car mileage with one of
these GM vehicles if properly fitted.

BTW, the buick seems to achieve better mileage than the Chevy or Pontiac versions."

I know of someone with a Chevy Lumina (streamlined minivan?) that claimed 35 mpg on the highway...has the 3.1 L.

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General Motors 3800 V6 gets good mileage?

RoadWarrior's picture

Seems to me to be a combo of the ECU the 4 speed auto they use and those 60 degree V6 motors. I had a S15 Jimmy with the 2.8 and the 4spd auto and had good highway figures from it. Sucked around town, but it was a TBI on that one.

Had "something to do" with a 3.1 in a Corsica/Tempest a while back which also was pretty reasonable on the highway.

Buicks I have also heard to have better mileage, their aerodynamics often look a bit better to me, so maybe that's significant.

Despite the good mileage though, both those vehicles had a lot of problems and were full of incurable "GMism" due to which I have ~'86 to mid 90s GM vehicles down on my "avoid like the plague" list. If you've had good luck with GMs of that era, you're lucky. My particular beefs with them are.

i) Absolute pigs to work on, tight engine bays etc.
ii) Excessive use of stamped parts where machined or cast would be more appropriate. You often have to beat and shim parts to fit.
iii) "Failnasty" design, as opposed to failsafe. One component or system failure seems to cause cascade failure in other components very rapidly and dangerously. Not under particularly high stresses either, normal driving conditions. Examples of that would be a "Titanic" design in the dual circuit brakes, meaning the good circuit can drain all it's fluid to the compromised circuit.... also 2 aquaintances who've have had a wheel fall off while driving. Only cars I've heard of it happening on.

Anyhoo, seen enough to tell me I don't wanna trust my life to one. Okay they feel okay to drive, those folks who just get everything fixed that the guys at the kwik-e-lube says needs fixing would never realise how much of a slender thread they were or might find themselves dangling by. Solid drivetrains, sucky everything else IMO, I'd rather have to baby the drivetrain and not worry about whether my next attempt to stop or turn would be my last. If you wanna drive one and be safe, replace all suspension joints and bushings yearly, ditto all brake parts. Maybe there were better quality bits on the olds and buicks.

That aside, there was a bit of an improvement in them in the mid-late 90s, and some models hold up pretty well, the Lumina/Transport for instance. I'd consider one of those I think. I did all the figuring for finding a vehicle that was good on gas but could tow 3000lbs and ended up with the Pontiac Aztec of all things. (You'd be surprised how few vehicles other than fullsize trucks can manage over 1000 these days) Jeebers is it ugly but you'll note a similar roofline to the Prius however.

An interesting project in that regard, for FE and some towing ability, might be to get an '84-86 Jeep Cherokee (Yes I know it's not a GM) that had the carbed 2.8 V6 in it, and retrofit that with a EFI 3.1 and GM 'lectronics. However, since some of the benefit appears to be in the tranny, then might need to figure out a way to make that work in there also.

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General Motors 3800 V6 gets good mileage?

diamondlarry's picture

I have a '92 Gran Prix with the 3.1 and 4-speed auto that I got 34 mpg on a trip from St. Louis, MO to Elkhart, IN. I even drove 70 mph between St. Louis and Indianapolis. If I remember right, I made 2 trips and got about the same both times.

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General Motors 3800 V6 gets good mileage?

E=mc2's picture

Interesting specs on a 1990 Lumina APV:

3.1L V6 gas

Horsepower: 120 hp @ 4200 rpm

Torque: 170 ft-lbs @ 2200 rpm

.....torque peak at cruising rpm?

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General Motors 3800 V6 gets good mileage?

fltcoils's picture

I've missed out by being away.

Buicks have been built for old farts (and I like an old fart car)

My 2004 LeSabre will do 22-23 city, and 32-39 highway (65 vs 50 mph)

The 3.8L is a 90 deg v6 derived from a v8 back in 1963. iron block, heads, pushrods, 2 V /cyln.

What's special about it?
1) CD =.31 for the car, it is slippery.
2) RPM = 1400@60
3) Cam set for low end torque.

As mentioned in other posts,
Engine friction increases with the square of engine speed
Engine efficiency at wide open throttle, full air charge is over double that at vacuum (pumping losses and combustion mechanics)

Designing for old farts one can:
Gear cars with a multispeed tranny (especially an automatic) to run low rpm (like 1000) on the road.
Cam engines for low speed efficiency (sacrificing "power" at the >3000rpm operation)
Shape the car based on 100 year old knowledge on streamlining (raindrop shape, blimp shape) rather than square back.

And the buick has plenty of zoom.

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General Motors 3800 V6 gets good mileage?

diamondlarry's picture

It's good to see you back again.

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General Motors 3800 V6 gets good mileage?

Al's picture

Plus the 3800 doesn't have the intake gasket problems the 3.1 and 3.4 engines have.

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General Motors 3800 V6 gets good mileage?

bobkrack's picture

fltcoils wrote:

I've missed out by being away.

As mentioned in other posts,
Engine friction increases with the square of engine speed
Engine efficiency at wide open throttle, full air charge is over double that at vacuum (pumping losses and combustion mechanics)

Fitcoils,
Good to see you back.

Can you point me to a descriptive definetion of "pumping losses"?

Thanks,
Bob

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General Motors 3800 V6 gets good mileage?

fltcoils's picture

I posted some links to the UMICH engine lab last year. They did some tests on efficiency etc.

Last I read, on discussions of the miller cycle or Atkinson cycle, pumping losses were claimed to be 20% loss or so. The engine test stand results included other efficiency boosts, to get that doubling.

The inspiring point I'd share is that efficiency in the "normal" IC engine is possible. The buick century does even better than the Lesabre using similar design but with the 3.1 L and a 60 deg V6. typ 35 mpg on highway, even going fast... And the Chevy Cobalt I rented did 42 on the highway at 65mph in LA traffic, 50 on a 2 lane going 50 mph. So there are mainstream cars doing well. Ernie Rogers gets 60-70 in his diesel VW, no heroric efforts either. he wrote it up at max-mpg. Slippery car, with good efficient engine.

The Killer is all that energy flushed into brakes everytime you stop. Larry avoids this problem by coasting to a stop, or not stopping (I think). He also runs the pulse and glide, to avoid pumping losses. Eventually we'll all have a motor/generator on the flywheel and capacitors to retain that energy. Of course a "mainspring" would do (I know that sounds dump, but I believe in K.I.S.S.). Ford/Eatons hydraulic launch attempts this, now being fielded for garbage trucks I think I read.

How do I get my avatar of my dad and his service truck back up??

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General Motors 3800 V6 gets good mileage?

SyntheticShield's picture

As the current owner of a Series II 3800 L67 motor, I'll have to say that I am impressed with the mileage you can get out of the thing. When I first bought the car it got around 28mpg all highway runs.

I have played with it a little (read: modified) and Im up to around 34 mpg all highway now. If I drive sensibly (read: no jack rabbit starts or WOT runs say from like spirited driving or track days) I can get a combined city/highway mileage of around 28 - 29, about 65% highway and 35% city.

I keep very close tabs on the mileage and fuel useage. I hope to soon be able to hook up with mpgmike and get some groovy heads, power lynz and so on and see if I go over 40 mpg which I dont think would be all that bad for a supercharged engine.

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General Motors 3800 V6 gets good mileage?

SyntheticShield's picture

I should add that I had an '89 Grand Prix with a 2.8L motor in it (V6) and I consistently got 36 mpg out of in on the highway.

With my current Grand Prix (2001 GTP) I fill up on Monday and I can drive all week to and from work and in town and still not trip the fuel warning light and fill back up on Monday. On weeks I get a little spirited I may be at the warning light. I had around 330 - 340 miles on the tank this morning when I filled up and I hadnt even hit the 1/4 tank mark.

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General Motors 3800 V6 gets good mileage?

MADDSCIENTIST's picture

I just wanted let everyone know that my mileage last week was 39 mpg in this big Oldsmobile. :shock:

I couldn't believe it. I am burning acetone and xylene in it but no other modifications.

Does anyone have any other easy suggestions to increase mileage? :wink:

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General Motors 3800 V6 gets good mileage?

Pinhead's picture

Holy cow, and I'll bet you that thing'll downright move down the highway.

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General Motors 3800 V6 gets good mileage?

SyntheticShield's picture

MADDSCIENTIST wrote:

I just wanted let everyone know that my mileage last week was 39 mpg in this big Oldsmobile. :shock:

I couldn't believe it. I am burning acetone and xylene in it but no other modifications.

Does anyone have any other easy suggestions to increase mileage? :wink:

What ratio of acetone are you using. I went up to 5oz/10gal but never saw any change at all in mileage. Though I have the L67 motor which requires premium gas and I have suspected that acetone doesnt have the same affect with higher octanes. Ive tried Acetone in two vehicles now, both required premium gas and I never saw any changes in mileage.

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General Motors 3800 V6 gets good mileage?

E=mc2's picture

MADDSCIENTIST wrote:

I just wanted let everyone know that my mileage last week was 39 mpg in this big Oldsmobile. :shock:

I couldn't believe it. I am burning acetone and xylene in it but no other modifications.

Does anyone have any other easy suggestions to increase mileage? :wink:

* engine/trans/diff additives

* front air dam

* larger tires

* Condensator

* EFIE

* special plugs

* hot air

* intake air temp sensor mod

* warmer thermostat

* blocked grill openings (Not rad or AC)

None all that easy...but doable.

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General Motors 3800 V6 gets good mileage?

diamondlarry's picture

E=mc2 has a good list there. I would like to add airing the tires to max sidewall(at least) to the list as well. This one is free. :)

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General Motors 3800 V6 gets good mileage?

E=mc2's picture

On the other hand...if I saw those kinds of mileage figures with a big car like that I might be afraid to mess with it...might jinx it? :lol:

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General Motors 3800 V6 gets good mileage?

MADDSCIENTIST's picture

Thank you for the list of easy mods. I will try some of them.

I have inflated the tires to 60 psi, but blew out the front 2 tires due to dry rot. The car was only driven
2000 miles a year for the last 5 years.

My acetone/xylene mix is: 2oz of each per 10 gallons. I added some boric acid to the mix a few times to see what would happen.

Thanks to everyone who replied for making this an interesting topic to discuss. :smt024

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General Motors 3800 V6 gets good mileage?

Al's picture

I have inflated the tires to 60 psi, but blew out the front 2 tires due to dry rot. The car was only driven
2000 miles a year for the last 5 years.

Don't the tires have a max pressure of 44 psi printed on the side of the tire?

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General Motors 3800 V6 gets good mileage?

MADDSCIENTIST's picture

I checked the side wall max pressure 68 psi.

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General Motors 3800 V6 gets good mileage?

diamondlarry's picture

I'm currently running 60+psi in my Prius tires.

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General Motors 3800 V6 gets good mileage?

ilikenwf's picture

I am a Tire Technician...it really isn't a good idea to go over the max PSI, and you should loosely follow the guidelines of the factory, give or take 5-10 psi. Its a big problem mpg-wise if you are running below 35 psi for most cars and light trucks, but I don't think I would run 60 psi in a prius, as those aren't very high load-range tires, and as it heats up in the summer, and your tires get hot on the road, PSI can go up 20-30 lbs.

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General Motors 3800 V6 gets good mileage?

diamondlarry's picture

In my Saturn I ran 60+psi in Goodyear Assurance Comfortread tires for nearly 10K miles with no ill effects. The tires were rated at 44psi on the sidewall. Some of those miles were at freeway speeds. I have heard that tire manufacturers have built in at least a 50% saftey margin for max psi ratings. I have checked tire pressures on my Prius right after driving in 85F temps and have found, at most, 2-5 psi difference from the cold pressure even after 10+ miles.

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General Motors 3800 V6 gets good mileage?

RoadWarrior's picture

What makes tires hot though is rolling resistance and a big part of that is sidewall flex. So actually they stay cooler if you run them at higher pressures.

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General Motors 3800 V6 gets good mileage?

E=mc2's picture

I would be very careful with the higher pressures and some tire/wheel combos. Generally the higher the pressure...the less contact surface. Get into a furball and you might find yourself skating on asphalt?

I'm generally running close to the max the sidewall. But I always test for traction...this is the FUN part.

With some 75 series on a truck I found that getting up near the sidewall max gave better traction as the tires on the front were slopping on the corners. Now they do the corners much cleaner.

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General Motors 3800 V6 gets good mileage?

RoadWarrior's picture

I've twice had to make emergency manoeuvres on tires inflated to sidewall maximum at highway speeds. In both situations, contact was avoided by mere inches. I think if I had had them at squabby stock pressures the delay in steering response could have killed me. You think that's exaggeration, but at 60mph 1/10 of a second is 8.8 feet. They also break traction more gracefully and predictably, with a smoother transition. With less pressure, you can have the back wheels juddering so bad that the front break traction also. Anyhoo, personally I prefer the handling on harder tires. When the sky poops they're back down to stock though.

Back to the topic, I'm always getting confoodled between the 3.8 and the 60 degree V6es, I guess because the bolt pattern is the same and they can be swapped 'tween vehicles easily. Noticed the other day that Lumina APV and TransSport with the 3.8 get better highway mileage than with the 3.1.

Was wondering actually whether one could put a 3.8 in something like a Buick Roadmaster in place of the V8. Not sure what the bolt pattern diff is between those apps.

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General Motors 3800 V6 gets good mileage?

apgrok1's picture

I think this trend goes across the board on all cars. For crying out loud, I have a Cirrus with a 2.4L engine in it and have never been over 30mpg even on the highway! Twenty years ago, a car that size would get 35mpg. It is a high revving, 4 valves per cylinder engine that has a final drive in the tranny of 3.94!
The 3.8 liter engine probably has 3.23 gears with a .75 overdrive, ending at a 2.42 gear. It is becoming obvious that you need as much torque at the lowest rpm possible to increase the engine's efficiency. Its so sad for me that my wife's Kia van has a 3.8 L in it and can get 24mpg at 65mph. It runs about 1900rpm at that speed. AARGH!

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General Motors 3800 V6 gets good mileage?

SyntheticShield's picture

The Grand Prix GTP I have has 2.93 gears. I dont recall at the moment what the 4th gear overdrive ratio was but it seems like it was in the 70's.

However, the 4T65E tranny had gearing different depending on the trim level. GTP's got 2.93's (and I still have traction issues. I'd love something in the 2.70 range), GT's got 3.29 gears and the SE's got 3.93 gears if I remember the numbers correctly.

I turn a tick over 2000 rpm at 70mph and Im pushing 34mpg. Not too shabby I think for a supercharged car. Definitely more than I expected to ever get and if I can ever get the funds together, I will be having Mike do some head work for me, my goal being at least 40 mpg but I would love to be in the mid 40's if not higher.

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General Motors 3800 V6 gets good mileage?

MADDSCIENTIST's picture

I just wanted to update on where I am with the Olds today. I recently installed a cone filter to draw in warm air from under the hood.
The original setup had almost a ram air thing connected to the inside of the grill.
I reset the ECU for this mod. Is there anything else I should do?

Michael

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