10w-40 motor oil in lawnmower engine?

[old1]

Yes, that IS what Tecumseh used to say. I was to factory schools, and they stressed that, and the reason was because in those days the 10w40 would sheer down pretty bad and pretty fast in air cooled engines especially in hot weather. Of course this was 30 years ago you must remember. They even showed us how to tell if an engine was using 10w40 by the color of the plastic governor gear. Non of which holds true with todays oils of course. And of course Tecumseh is no more.

 

[bubbatime]

This thread is like 8 years old, so I dont think the original poster even cares any more.

But YES, modern 10W40 is fine. They used to put that warning in the manuals back in the 780's and 80's when the 10W40 of the day would turn into goop.