Originally Posted by BigCahuna
My 1997 mower calls for straight 30 wy oil. But over the years it's had alot of different brand and weights in it. And it runs the same. By looking at what eveyone else uses, from used oil from their cars, to special "mower use only", to specific API grades, it's obvious you can use any oil you like and whats handy, and the mower motor will outlast the rest of the mower. The biggest danger would be hitting that hidden rock or tree stump and bending the shaft. Then all that special mower use only oil won't mean much to you, as your rolling it out to the curb on trash day.,,,,
This.
The most common killer of mowers from what I've seen are:
1. low oil (usually no oil)
2. Mice nests (see #1)
3. stumps/rocks bending crank shafts
4. wheels rusting off the deck
The most common situation is the mower sits outside or in a shed over winter, mice build nests in the cooling shroud, and the mower overheats which burns up all the oil in the crankcase after a couple uses. This process is sped up by a engine that is either already low on oil, or an engine that already burns oil.