[Rack776]

What do you guys think is a respectable M.P.G.
for a 455? Any improvements I can make?

I recently took a vacation day and put a few miles on my T/A
I decided to keep track of the Fuel used & miles driven.

The car is a mostly stock 1975 Trans Am with a 455, 4 speed, 3:23 rear,
no A/C, 068 RA/4 H.O. cam, MSD Ignition, hedders & 2.5" flowmasters
re worked 72' 455 HO quadrajet, stock 6H heads.

Over 318 miles driven thru Philadelphia to the New Jersey shore
75% Highway at about 55 to 65 MPH
and 25% stuck in Toll Booth & Philly traffic "stop & go"

I averaged the MPG and got 16.5 MPG

Is this pretty good or pretty bad for what I have?
range between fuel stops was about 90-100 miles to get there & home.
I used mostly 89 octaine, it does not seem to care what it runs on with the
big chamber 6H heads so I went with the "cheaper" gas

I really tried to go easy on it and pulled about 20-24 inches of Vac.
at a cruse speed, and about 2,500-3,000 at 60 MPH

I learned alot about saving some fuel with the vac gauge,
3rd gear at a slightly higher RPM pulls more Vac than 4th gear at a lower rpm,
the 455 has so much torque & pull its sometime hard for me to judge
when to down shift. I always assumed the Higher RPM is what used fuel
faster, Using the gauge works great so I'm glad I installed it.

I also learned its VERY hard NOT to put the pedal to the floor when doing
a long range M.P.G. test on a car with a 455 LOL!

[rohrt]

My 77 GP use to be set up pretty close. It got 13-17 so I would say your in the ballpark.

[Mark C.]

My TA gets 17 highway (70-75mph) and 14.5 around town. It's far from stock. Dynoed at 420hp and 520 torque.

Heck, my 70 Bonne w/360 horse 455 in it gets 18 and 13, and it's bone sock.

I wouldn't worry to much about it.

[1971/455/HO/4-SPD]

I would say you are doing quite well for that combination!

[x-bird2]

you're doing fine, i run on the smiles per mile meter. if i were to think in terms MPG, with mine in the single digits i'd never enjoy driving it!