[1Mike2]

What weight oil do I put in my 20 horse power riding lawn mower ?

[Dr1757]

I have a sears 21.5 hp rider and sears recommends 30wt. Be sure to check the oil level before each use.

Hope this helps.

[KISS]

Non-Detergent oil. Typically 30 W ND.

[MOWERMAN2468]

It depends on the manufacture. Different engines use different weights. Perhaps I should not say it depends on the mfg, because some mfgs will use different wts. For similar engines. Take Kohler for instance, they use sae 30 AND sae 10w30.

[Northern Mike]

1Mike2,
Different manufactures list different weights for different outdoor temperatures.
I use mostly sae 30 in summer. Use 10w30 or 5 w 30 in winter.
Mike