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What kinda MPGs witha stock 3.8 2v? UPDATED

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shotgun
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What kinda MPGs witha stock 3.8 2v? UPDATED

Post by shotgun » Sat Jan 01, 2011 5:43 pm

I put a deposit on a car finally.

The plan is to drive it and see what it needs and then build from there.

What kindas MPG can I expect?

It is a 85 Bonneville 4 door.
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'Bu-Camino
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Re: What kinda MPGs witha stock 3.8 2v?

Post by 'Bu-Camino » Sat Jan 01, 2011 6:00 pm

Well.....just for reference I had an 81 g-body in college with that engine. The rear gears were something in the 2.90 range and I kept it under 70. MPG was about 18 or so if I remeber correctly. Lots of variables though in these age of cars.
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Re: What kinda MPGs witha stock 3.8 2v?

Post by shotgun » Sun Jan 30, 2011 7:27 pm

Ran the codes , this has a 2.41 rear . The trans upshifts way early so she is a dog in drive.

Tried just leaving it second and feels pretty good, engine is in it's power band.

Does not feel likes it's revving cruising at 45.
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t5montecarlo
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Re: What kinda MPGs witha stock 3.8 2v?

Post by t5montecarlo » Sun Jan 30, 2011 7:58 pm

2:41 would have been my first guess.

I would expect the rated mpg was about 20/24. Have you been able to find any documentation citing original mpg ratings for the car?

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Re: What kinda MPGs witha stock 3.8 2v?

Post by bukweet » Sun Mar 06, 2011 9:06 am

My longroof had 2:73's from the factory.

Was a pretty good gear for the 3.8 buick V6.

I put 3:42's in it and while it woke it up, it was way to tight at highway speeds with a turbo 350 transmission. Overdrive or a lock up convertor would been a great thing to have.
Put some 255-60-15's on it and took a few rpm out of it.

If you do nothing but city driving, 3:42's would be cool.


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Re: What kinda MPGs witha stock 3.8 2v?

Post by t5montecarlo » Sun Mar 06, 2011 9:20 am

Are you considering changing the gears and using the wagon T5?

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Re: What kinda MPGs witha stock 3.8 2v?

Post by shotgun » Fri Apr 29, 2011 11:07 am

Finally got my 85 Bonnie inspected and on the road.
Ran a tank of gas threw before started keeping track of MPG , had to fix the trans etc.
Anyway , getting a hair under 17 mpg.
That is suburban, drive to work, driving, rarely sees over 50 mph. Did get the a/c working and used that 1/2 the time.
What are you other 3.8 V6 guys getting?
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Re: What kinda MPGs witha stock 3.8 2v? UPDATED

Post by t5montecarlo » Fri Apr 29, 2011 7:20 pm

I used to be able to squeeze about 18 in the wagon on 35-45-mph roads going to work and back. A lot of time was spent in 5th gear.

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Re: What kinda MPGs witha stock 3.8 2v? UPDATED

Post by dragonmaster093 » Sat May 19, 2012 10:53 pm

i get between 16-18 depending how i drive and what roads i take (ie. flatter ones or hills/mountain roads)

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Re: What kinda MPGs witha stock 3.8 2v? UPDATED

Post by Darwinskeeper » Mon May 21, 2012 2:43 pm

The last time I checked, Darwin's anything but stock 4.3 was getting 16-18mpg in mixed driving even with a leaky 4160 and 2.41 gears.

Her best mpg was recorded during my only major road trip back when she had 2.73 gears, a Comp 252H camshaft and a freshly rejetted Holley. I saw mileage in the low 20s running 65-70mph with the windows up and the AC running. My best mileage was 24mpg at 65mph
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Darwin, a 1979 Malibu Wagon with a 3 speed Manual box and 2.41 gears in back
Engine is a '85 4.3 V6 topped by an Edelbrock Performer and a 465cfm Holley 4160. The heads have a 3 angle valve job and the cam is a Crower Level 1 240HDP grind with Comp Magnum 1.52/1.60 rocker arms. Full headers with 1 1/2 primaries dump into duals with 2 1/2 tubes and turbomufflers.

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Re: What kinda MPGs witha stock 3.8 2v? UPDATED

Post by toyodajeff » Sat May 26, 2012 9:00 am

when my el camino still had the chevy 3.8 I got 21mpg's on on the highway going 55. It had a rebuilt 229 with all the emissions equipment removed, a th350 and I'm pretty sure 2.73 gears

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