I have 3, m-18's I use detergent as the engines have oil filters, if they didn't I would use non detergent.
Detergent tends to keep particles in suspension that a filter removes
(or that is what they say anyway)
30 W dino oil is just fine.
These are not high compression or turbo/supercharged engines that would benefit from synthetics.
Kohler likes them to use 30W oil in warm temps, if one is using them to blow or push snow, that would benefit the ease of starting by using a multi-weight like 10W30.
Now if one wanted to use the most expensive oil available, no problem.
if one keeps the snow equipment in a heated building, 30W would perform just fine,
or if all one had to use was 10W30 in summer because it was all they had at that moment it would work, although they would experience increased oil consumption, and it would thin out more at the higher operating temps of the aircooled engine in warm/hot weather, so for those reasons they recommend 30W.
It is more important to change the oil regularly than anything else, along with giving the engine time to warm up before puttin' the spurs to it!
I change the mower oil every spring (about 80/100 hours)
depending on the cutting season, and if I do neighbors that can't seem to keep their new junk operating.
Now this is my opinion and I'm sticking to it.
Other conditions or people's wants/ needs will vary and is just fine.
