On 26 Apr, 11:39, zzapper wrote:

I've just bought a new petrol mower after my old one died after 18
years service, and find it specifies LawnMower Oil. Is this a con and
will any good quality Motor Oil 20/50 be just as good?

I would not put multigrade motor car oil in an air cooled engine. It
is likely to get very thin when the engine gets hot.

I would recommend the specified oil - a one pint bottle will last a
very long time, and I don't think that motor oil is particularly cheap
now anyway.