Hi.What should be gasoline for cadillac1965

Back then, gasoline had a lead additive that protected the engine's valve. That lead was bad for the environment and catalytic converters, so it was no longer used after about 1978. However, you can go to the auto parts store and ask for an additive to use in your vintage Cadillac. Ask your friends, who have older cars, what they use.

I would run premium with a lead substitute additive. There are a number of products that are marketed for use in older cars so do your research. I would also use ZDDP in the oil.