What weight oil is best for a rotary? The manual calls 10w-40, but most newer (piston) engines use a much lighter 5w-30 partly because the thinner oil causes less drag and improve mpg (I said partly!). Will the same thinking go for the rotary? My car has been pretty good with oil (2.5k since last oil change and down only about 1/2 QT.), so I'm thinking I should go with the thinner oil for the cold Wisconsin winters.

What say the experts?

Thanks

 

The FAQ has a chart from the factory service manual. Oil weight should be chosen by temperature range in your area.