Kyle's 77 Cutlass

Hey guys, whats the guesstimate of fuel mileage for a 72 455 with Ga heads running 3:73?

Jerry the wrench

12.....what do I get if I win?

oldspackrat

I'd guess maybe 10?

Kyle's 77 Cutlass

Okay, just wondering. Thinking of swapping my 350 in tnx and transplanting a 455

oldcutlass

Around town 6-10... the fun factor is priceless.

DLaz70OLDS98

If your concerned about mpg than you shouldn't be thinking about a 455.

Bfg

Back in the day $2.00 worth of Ethel would let you cruise all night long!

oldstata

X2

8 hwy and 2 around corners is my guess

Kyle's 77 Cutlass

My 350 is making 10 now. So a 455 with more torque and hp, priceless.

dc2x4drvr

8

steverw

Depends on how you drive it, anywhere from 7 mpg if your trying to conserve to 7 blocks pg if your havin fun with it.

Steve

hullinger

My '73 Custom Cruiser with 2.93 rear gearing consistently gave me 11 MPG of spirited around town driving. I did get 14 MPG once when I burnt half a tank on the highway running consistently at around 70 MPH. I will say however that 11 MPG was a welcome improvement over 7 MPG, which is what I was getting before leaning out the carb.

It's amazing what the different metering rods will do for your mileage.

Chris

MDchanic

My 350 makes about 14-16 on the highway pushing a fullsize Delta that's crossed the scales at the local quarry at over 5,000 pounds, through a 3:08 rear and TH400.

You must be having a LOT of fun to get 10 out of a cutlass.

- Eric

Vandy

if your getting more than 3 gallons per mile your doing it wrong.






I think mine got 6ish?

nsnarsk65cutlass

5 at best

Kyle's 77 Cutlass

Okay thanks for the input guys

rjohnson442

I average 6-7mpg in my 72 (461 with a 850cfm carb) No vac advance and 2.7 gears car weight is 3720 with me in it and half a tank of gas. I get the best milage out of her @ speeds around 40-50 mph. Now if I stomp on the gas and do a nice pull just once that all goes out the window and drops me down to around 5 mpg, which usually has to happen a few times when I'm in the car

Oldzee

Man I gotta tell ya, I'm glad to read what everybody's getting for mileage. I'm new to this as I just got my '72 Hurst back in June and so far I've put about 170 miles on it. Used 2 tanks of gas to do it. Based on the 15 gallons I seem to put in each time, I figure the tank must be around 16 gallons or so? (The tank's never completely empty when I gas up). I figure I'm getting around 6 miles to the gallon with my open 3.23 rear (and open wallet). Love it!

twintracks

I averaged 18 mpg over 4,100 miles in the 2013 Great Race. Half of which was highway miles going to the start, and returning home from the finish.
'68 Toronado, stock 455 except for a Pertronics II ignition.

brown7373

As steverw said, it's according to how you drive it. My Olds is a 350, but I also have a 1970 Bonneville convertible 455 with a 2.93 rear. It's been off the road for a few years, but I came across a little book recording fuel mileage over a couple years. It showed mostly 13-14. Some of it down in the 11s, but some highway 15 to 16.


I know it is a heavy Pontiac with a much higher rear gear, but not much different than an Olds. Most of my cruising is done on cruise control, which helps the mileage.


Back in 1979-80 on a trip from Florida to North Carolina for Thanksgiving I got over 20mpg. Cool weather, no A/C running and the availability of leaded high octane fuel sure helped!

oldsmobiledave

I have a 0.060" over 455 in my 1980 GMC p/u. With T400, 3.73 gears & a 29" tall 235 75 15 tall tire on the truck I get 11 mpg cruising @ 65 mph. That is 11 miles per imperial gallon or 9.3 miles per US gallon. My truck weighs 5000 lbs.

BlackGold

Man, I can't believe how low some of you guy's mileage is. My '70 W-30 with 3.90 gears gets 10 mpg, whether city or highway driving. And it runs rich. Not that 10's great, but it sure beats 6 - 8.

76olds

I'd just drive er' and let the wife take it out when its close to E !!! Let her fill it up . Put-r-ther!!

Kyle's 77 Cutlass

Lots of input here. Wow

Kyle's 77 Cutlass

How much is it a hassle to transplant a 455 into a tnx?

Kyle's 77 Cutlass

Gmc

oldsmobiledave

It was a 5.7 diesel new so it was a breeze.

Gary M

Mines not for daily so I don't care what I get. Is yours for everyday use?

Kyle's 77 Cutlass

Ya that would make it simple.

Yes it is my truck I use spring to fall.

Gary M

Then I would find another 350 unless you are hauling massive weight. 350 has good HP and mpg. We need more info on this issue to help you further.

Fun71

A '72 should have a 20 gallon tank.

I mapped mine out back in the 80s and it's 15 gallons from F to E and 2.5 gallons from E to sitting on the side of the road.

oldcutlass

I guess you found that out the same way as the rest of us after saying "it's got plenty of gas left at E".

Oldzee

"A '72 should have a 20 gallon tank.
I mapped mine out back in the 80s and it's 15 gallons from F to E and 2.5 gallons from E to sitting on the side of the road."

Thanks for that info. I take it you weren't in a '72 at the time?

Fun71

'70 Supreme.

Magna86

My 71 was getting 13-14 city and 19-20 on the highway cruising at 60 with the 2.56 rear. Haven't driven it very far with the 3.08's since tires need replaced due to age and its sitting in storage.

jensenracing77

I was getting 15 in a 76 98 with a stock 455. How many of you are going by your odometer? That is not very accurate because most of them do not read correct anymore. Take a 10 mile stretch of highway and check it against the mile markers, You will find them off.

Kyle's 77 Cutlass

I pull my 7000 lb camper back and forth to work. When I do this, mileage drops to 5

Fun71

I had a speedo calibration box made for mine after switching out the 2.56 rear so it was just as accurate as when it left the factory. I guess that's just one more thing on my car that is not "factory original".