1970-1981 Pontiac Firebird/Trans Am (Second Generation) — MPG & Fuel Facts NO OFFICIAL EPA RATING

The EPA's public fuel-economy dataset only goes back to 1984 — the 1970-1981 Pontiac Firebird/Trans Am predates it, so there is no government-rated MPG number for this car anywhere, including here.

Estimated 12–20 MPG combined.

Official EPA Gas Mileage Guides for model years 1977, 1979, and 1980 show a well-corroborated spread from 12 mpg city (400 CID V8, 4-speed manual, confirmed independently in both the 1977 and 1979 guides) up to 20 mpg (231 CID V6, automatic, confirmed in both the 1977 combined and 1980 estimated figures); the 1980-81 turbocharged 301 CID Trans Am came in at 14 mpg. No verifiable period-measured figure exists for the earlier 400/455 big-block years (1970-74), which predate EPA testing.

This is our estimate, not an EPA rating — built from the period road tests, marque-specialist guides and corroborated owner reports cited below, hedged where sources vary. Treat it as a ballpark for planning, not a spec to rely on.

Second-generation Firebird/Trans Am engines ranged from a 231 CID Buick-sourced V6 up through 301, 350, 400, and Olds-sourced 403 CID V8s over the run, with manual or automatic transmissions. EPA Gas Mileage Guides read directly from scanned government documents give, for model year 1977 (231 V6/automatic): 17 city/25 highway/20 combined; (400 V8/manual): 12 city/19 highway/15 combined. The model-year-1979 guide (which reports estimated mpg via annual fuel cost rather than separate city/highway) shows 231 V6/automatic at an estimated 18 mpg and 400 V8/manual at an estimated 12 mpg — matching the 1977 figures at both ends independently.

The model-year-1980 guide shows the 231 V6/automatic at an estimated 20 mpg and, notably, the 301 CID Turbo V8 (the famous turbocharged Trans Am) at 14 mpg. A useful negative finding: no 4-cylinder 'Iron Duke' engine appears in any Firebird-line EPA listing through 1981 — the Iron Duke wasn't offered in the Firebird until the third-generation redesign in 1982, so no citable 4-cylinder Firebird figure exists for 1980-81 despite that combination sometimes being assumed.

No EPA data exists for 1970-74 (predates EPA testing), and no period magazine road test with a quantified mpg figure for the big-block 400/455 could be verified — Car and Driver's SD-455 coverage from this era focuses on quarter-mile performance, not fuel economy. A Hagerty buyer's-guide snippet claims a 1971 455 HO Trans Am 'never pulled better than 12 MPG,' but the source page could not be directly verified (blocked to automated fetch), so this is noted only as weak, uncorroborated color and is not included in the sourced range.

Sources: EPA Gas Mileage Guide, model year 1977 (EPA NEPIS archive, scanned original) · EPA Gas Mileage Guide, model year 1979 (EPA NEPIS archive) · EPA Gas Mileage Guide, model year 1980 (EPA NEPIS archive)

All classics Search Pontiac Firebird/Trans Am on FuelFacts (in case a later model year is in our 1984+ EPA data)