oil viscosity and detergent

[Chet]

I am searching for information on the use of high detergent oil and the viscosity I can use in my 1947 and two 1948 year cubs. What are the advantages and dis-advantages of changing to detergent 30 W or 10W-30 oil?

[John *.?-!.* cub owner]

If the engines have been recently rebuilt, I would go with the detergent type oil, which I have done with all of mine. If the engines have not been rebuilt in MANY years I would stick with the non detergent unless you know they have been running detergent type. The detergent keeps the dirt in suspension so the filter can trap it. If you make a switch and there is a lot of dirt and sludge in the engine you will at the very least, need to change the oil filter pretty often for a while.