For many decades, most American cars were equipped with inline-six engines driving the rear wheels, and the straight-six remained the base engine in many models even after the V8 became King of Detroit, then these cars became more compact, easily packaged V6 engine. However What was the very last rear-wheel-drive American car with straight-six power?
Assuming that only cars built for the United States market by major companies headquartered in the United States qualify for this distinction (that’s right, South Carolina-built BMWs don’t count, nor do trucks, nor do kit cars or single-digit-production-run cars, nor does the all-wheel-drive AMC Eagle), you might still feel that a BMW-engined Lincoln doesn’t make the cut. In that case, several 1983-model-year cars do qualify, among of them, the 1983 Dodge Diplomat and its Plymouth Gran Fury sibling, which could be purchased with a 225-cubic-inch Slant-6 engine.
The 1983 Ford LTD and its Mercury Marquis sibling were available with the “Thriftpower” 3.3-liter/200-cubic-inch straight-six, and a four-speed manual was the default transmission in these rear-wheel-drive cars (though most customers sprang for the automatic). The last year for a straight-six Mustang was 1982.
1983 was the last model year for the AMC Spirit, as well as the bigger AMC Concord, and both these cars had standard I6 power and rear-wheel drive. The AMC straight-six engine stayed in production into our current century (and no, rear-wheel-drive Jeep XJ Cherokees don’t count as cars). It’s possible that some fleet/taxi versions of some of these cars were built with straight-six power after 1985.