N/a mpgs?

91dime

Drop & Destroy
Joined
Mar 8, 2007
I know this is a topic that most guys don't worry about when it comes to their 231, but I'd like to know about it. I'm looking at buying a 1978 Buick skylark 4 door to be my everyday driver. I understand this car isn't made to be a high mpg car, but i'm thinking it won't do terrible, and it will be super easy to fix comparerd to my current dd. So you guys out there driving your n/a 3.8s, what kind mpgs are you getting?

This car has super low miles, and is the right price so I'd really like to buy. It's also a perfect canidate to turbocharge and make the ultimate sleeper!
 
If you're gentle on the throttle then you should be able to get 20 MPG on the highway. As far as street MPG I'd have no idea.
 
I'm hoping to get a little more than that. I have read that people claim 25 mpg, bit that seems high.
 
The car in my sig and avatar got 21 mpg on my 700 mile trips back to school....25 years ago. Ran a best of 19.72 @ 72 mph in 2nd gear at the time. GB
 
Mine gets 19 going 70 down the road and up to 21 at 55. That is a 3.8 bored 40 over with a carb turbo and an unknown rebuilt carb. Wouldnt be suprised if I could get 25 with a carb running the PECV valve and 84/85 headers and my new DP. Should take out some restriciton.
 
There would be some modifications I could do to get better mpg. Can you guys recomend anything in particular?
 
There would be some modifications I could do to get better mpg. Can you guys recomend anything in particular?

Leave the two barrel carb on. Remove as much metal off of the car. Replace with aluminum drums, bumpers, trunk, hood or custom fiberglass if these things are available. There are no mods you can do in the mechanical area for better MPG. Reduce the weight and your MPG will go up. Mod with HP upgrades and your MPG will go down.

My 1981 Regal OEM, 20,000 miles on it @2700 LBS, dueljet, max @55MPH highway 20-21 MPG. Best I can do now is 18 highway. Local streets is at best 15 and with A/C on about 12.
 
What do you think a trans with od would do to the mpgs? I dot know what the car has in the rear end stock, but I could possibly get a higher ring and pinion set for the rear end. I hate to pull off the original panels because this car is mint, but your right, that's probably the only way to get bettter mpgs.
 
The stock transmission is a THM-350C, which does'nt have OD. Stock Gears were 2.41. I beefed up my trans and replaced the rear gears to 3.23. The higher spin on the highway would suggest more fuel usage.
The higher the gear the more the car needs an OD transmission.

My spin @ 70MPH before the higher gear was 2800-3000. Now she's spinning 3800 @70MPH.
 
Thats what I meant by a higher gear, I have my terms backwards. I thought the car would have 3.23s stock, but 2.41s are even better. What about those 2.41s with an od trans? It be sweet if I could afford a mpfi setup, that wouldn't hurt.
 
SAY WHAT? Fred I've swapped my gears for 3.42's and I'm using a three speed and I'm under 3000revs at 70mph
 
Tire size makes a difference Adam. He probibly has smaller tires on it.

It just occured to me that it should have a mechanical advance on it. You can squeeze a little more mileage out of it by using MrGasket advance weight kit and recurving the distributor some. A little more advance in the curve and it will get better throttle response and better mileage.
 
I had an 84 Regal LTD 4.1 with Quadrajet and 200r4, 2.xx gears (don't remember). Car was all stock (except shift kit to firm up 2-3), but kept it tuned and in good order. It would get excellent mileage, almost always above 20 and even better on the highway. I wish I remembered exactly, but got mid 20's many times I checked it. You'd need the OD for the highway though, but I guess you could swap if you really wanted to. I took it to the track once and it ran 17.8X for like 10 hot laps and would bark 3rd gear, but not 2nd :D. I actually still have it, parked close to the 83 for parts. It was my mom's car and looked great with my TType. I'd think your 3.8's mileage would be acceptable and could be improved with gears and an OD swap.
 
I forgot Ill need to get a 200r4, not a 700. How hard are 200r4s to come buy. Yeah I do alot of highway driving to school and work so od will make a difference. Ill look into that weight kit, how do I select the right one? Are there different kits for different rpm ranges?
 
You could also get a TBI(Tuned Barrel Injection) to replace you Carb and also the 200r4 trans would both help... that`s what I plan to do with my 78 Regal when I get it running again. It was my DD too. It has a N/A 4b carb right now and it wasn't the greatest for MPGs... but I`m also a LED foot though:biggrin: If your soft on the gas(slow) than it isn't too bad, but its not my style:biggrin:
 
I forgot Ill need to get a 200r4, not a 700. How hard are 200r4s to come buy. Yeah I do alot of highway driving to school and work so od will make a difference. Ill look into that weight kit, how do I select the right one? Are there different kits for different rpm ranges?

There only one kit. It has everything you need in it as well as instructions. I've always used the lightest springs in it to get the earlyest advance out of the distributor. You'll also need to retime the engine to get it back to stock timing but that's minor. If you experience any knock just cut the initial timing back slightly and you should be ok. On a late 70'd engine I doubt that you will but you never know.

And Jase, it's throttle body injection.:biggrin:
 
SAY WHAT? Fred I've swapped my gears for 3.42's and I'm using a three speed and I'm under 3000revs at 70mph

Oops! :eek:....meant 2800 RPM's, (3.23) and 2000 with the 2.41's. :biggrin:
These are 215/65R15 tires.

Owning four stock 3.8's with Dueljets and the best mileage I've ever had was 21 MPG's. Anything more then that I would consider extraordinary!
 
200r4 shouldn't be hard to find. The BRF's (stronger for later GN and T)are hard to find, but not necessary. I've got a couple and just rebuilt one (the one out of my 84, still shifts hard to 3rd) for under $150 and am using it as a temp in my GN until I get the BRF finished. My 83 T had 'one and most all 84 up regals I've seen or owned had 'em, so there should be many of them around in other applications just sitting. I'm sure one of the experts can give you a complete application list. Or you could use the 700 with BOP or get adapter if not I would think. You're in WV, so like in KY there should be alot of inexpensive options.
 
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