what kind of oil to use...

right..use 30w detergent (HD) oil. lucas the mower man.

If it still has good oil-control (doesn't leak or burn much), I'd go for one of the higher-vi synthetics. Makes for a "happy" engine, IMHO.

I think Briggs reccomends a good brand of 10W30. Penzoil and Castrol are good.

Every mower I've had recommended straight 30 wt.

Bob

I will double on that. I switched to 5W30 Mobil 1 on all my air cooled engines. It can stand heat a lot better than conventional oils. Don't worry about the 5 rating. That is only when very cold. When warm it still has 30 weight viscosity and is a bit easier to start.

I have a 45 year old B&S engine that runs like new using it.

Not any more. They all say multi-weight is also good except that since air cooled engines run hotter than others the oil level should be checked more often. The solution for that is to use synthetic which will stand up even better than straight weight. Synthetic is really considered to be like a straight weight except it doesn't get as thick when it gets cold, therefore can meet the multi-weight classification.

Just everyday straight 30 will be fine. That's all i run in over 100 pieces of small eq, and 33 trucks at the landscaping co i work for.

small engines haven't changed. The only reason they are recommending the multigrades is for emissions ratings. Also, it is more likely someone will have a multigrade on their shelf than a straight weight. Small engines use straight 30.

But what I am saying is that synthetic multi grade such a 5w30 really is a straight weight. That is the way it is made. It doesn't get as thick when it gets cold and is far superior for small hot running engines. It doesn't have all or need those Viscosity Improvers used to make conventional multi-grade.

Just take a look at the manufacturers literature and you will see they even say multi-grade conventional is OK.