How to Choose the Correct Viscosity of Oil for your Classic Vehicle

Ken Tyger and Nick Dixon, with PennGrade 1 high performance oil, talk about how to choose the correct viscosity of oil for your vehicle.

The engines of classic cars were designed for the viscosity of oils available during that time period. The engines of the 1950s - 1970s had much looser clearances than any of today's counterparts. Today's engines are built around fuel economy and emissions standards.

With a 1970 Oldsmobile Cutlass, you are without a catalytic converter. You should look at the engine in the ideal ambient temperature environment, between 60 and 100 degrees. For this vehicle, Ken would recommend a SAE 30, a straight weight monograde/linear viscosity oil.

In relationship to drain interval, it is dependent on how and when you use the application. Because PennGrade 1 is mostly conventional, mineral-based oil, we recommend users adhere to a 3,000 mile oil drain or once per year, whichever comes first.

For those who only drive their car for a few months per year, it is recommended to change the oil and filter at the end of the season, before the car sits in a garage for several months.