1971-1979 Cadillac DeVille/Eldorado — MPG & Fuel Facts NO OFFICIAL EPA RATING

The EPA's public fuel-economy dataset only goes back to 1984 — the 1971-1979 Cadillac DeVille/Eldorado predates it, so there is no government-rated MPG number for this car anywhere, including here.

Estimated 8–18 MPG combined.

Big-block 472/500 CID 'land yacht' era cars (1971-76) tested at roughly 8-16 mpg — Consumer Guide's own 1973 road tests measured 7.5-8 mpg, and the EPA's 1975-76 guides rated the same cars 11-13 combined. After the 1977 downsizing to a 425 CID V8 and a lighter body, the EPA's 1977 Gas Mileage Guide shows improvement to 11-18 mpg. Real-world owner reports for both eras cluster near the low end of each EPA figure.

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.

Both DeVille and Eldorado used a 3-speed automatic exclusively (no manual was ever offered) with a 472 CID V8 (DeVille through 1973) or 500 CID V8 (Eldorado all years, DeVille from ~1974) in cars weighing over 5,000 lbs. Consumer Guide's own period-test-derived list, 'The 12 Worst Gas Guzzlers of 1973,' states the 1973 Sedan DeVille (472 CID) measured 7.5 mpg and the 1973 Eldorado (500 CID) measured 8.0 mpg, sourced explicitly to Consumer Guide's own '73 Auto Test magazine testing.

The EPA's official Gas Mileage Guide (which began covering new cars in the September 1974 edition, for model year 1975) rated the same DeVille/Eldorado 500 CID V8 at 11 city/16 highway, and the following year's guide (model year 1976) rated it 12 city/16 highway/13 combined (or 11/15/12 with the factory EFI option) — both consistent with, if a bit more generous than, the Consumer Guide test figures.

GM downsized the full-size Cadillac line for 1977, dropping to a 425 CID V8 in a substantially lighter C/E-body; the EPA's model-year-1977 guide reflects this by reclassifying the DeVille as a 'Large Car' (rated 14 city/18 highway/16 combined) and the Eldorado as a 'Mid-Size Car' (11 city/18 highway/14 combined) — confirming the size class genuinely changed, not just the marketing. A 1978-79 EPA guide could not be located to confirm the 425 CID figures carried through unchanged, so those two years are extrapolated from the verified 1977 data rather than independently confirmed.

Independent forum corroboration (Grassroots Motorsports) has multiple owners of 1971-72 472/500 CID cars independently reporting 8-11 mpg city and 12-14 mpg highway cruise — closely matching the EPA/Consumer Guide figures for that era.

Sources: Consumer Guide — "The 12 Worst Gas Guzzlers of 1973" · EPA Gas Mileage Guide for New Car Buyers, Sept. 1974 ed. (model year 1975) · EPA Gas Mileage Guide, 2nd ed., Jan. 1976 (model year 1976, fueleconomy.gov) · EPA Gas Mileage Guide, 2nd ed., Jan. 1977 (model year 1977, fueleconomy.gov) · Grassroots Motorsports forum — "Early 70s Cadillacs and fuel efficiency"

All classics Search Cadillac DeVille/Eldorado on FuelFacts (in case a later model year is in our 1984+ EPA data)