Best small engine oil

What is the best engine oil to run in air cooled side valve engines such as my 1999 model Briggs Twin II 17hp, 1996 Tecumseh 4.5hp vert shaft, and a 1986 era Briggs 3.5hp? Manual calls for 30W but I know there's differences in formulations with different additives? Any recs?

 

SAE 30 of any decent quality is generally best for all of them.

 

I have friends who claim Shell Rotella is best because it has more zinc in it which is better for older engines. I bought some Rotella T1 at Wally but it is service grade CF and CF-2. Is this oil OK to use in my engines?

 

As long as it's SAE 30. There are more fruitful things to worry about than oil brands. It doesn't matter, just don't buy some no-name cheapo recycled oil or non-detergent oil from the corner convenience store. Most of today's small engines don't last anywhere near long enough to take advantage of hair-splitting differences between modern oil formulations. The cheap store brand oil is still much better than the oils we had years ago. I don't recall seeing an engine that failed due to not having a "good enough" oil in it for a long time. I have seen plenty that failed from not having enough oil, however. The ones that have regular oil changes and upkeep usually last about as long as the rest of the mower is usable.

The air filter and the seal around it... now that's a place to spend your concern. That's what causes the rings to disappear.

 

Thanks Cheese! I like to get max life out of all my stuff. The 3.5 Briggs I'm running on a 1972 model Snapper V21 that my folks had since new. I've patched a couple holes in the deck and replaced the wheels but it runs, bags clippings like a champ!