What kinda MPGs witha stock 3.8 2v? UPDATED

[shotgun]

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.

 

['Bu-Camino]

Re: What kinda MPGs witha stock 3.8 2v?

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.

 

[shotgun]

Re: What kinda MPGs witha stock 3.8 2v?

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.

 

[t5montecarlo]

Re: What kinda MPGs witha stock 3.8 2v?

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?

 

[bukweet]

Re: What kinda MPGs witha stock 3.8 2v?

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.


8)
bukweet

 

[t5montecarlo]

Re: What kinda MPGs witha stock 3.8 2v?

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

 

[shotgun]

Re: What kinda MPGs witha stock 3.8 2v?

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?

 

[t5montecarlo]

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.

 

[dragonmaster093]

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

 

[Darwinskeeper]

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