Hmm, the eighties. 69 GMC 1/2 ton with an inline 6 250 CuIn, Valvoline 40. Plymouth Roadrunner with built 440, Valvoline 40. Pontiac Fiero with inline 4, Valvoline 30. Never was a multigrade person back then. Dad always said 10W30 until it's starts using oil then 10W40 and finally straight 40.