Hello Bezalel,

The 20 weight oil should work, it is just a bit thiner than 30 weight. You may
have more oil coming out around the bearing with the 20 weight oil. I would
think that the 40 weight that you've been using should work fine.

Fred Holder
http://www.fholder.com/

In article .com, bizHB
says...

so far i've been using wd40 but today i went to look for the oil
recommended by record(motor oil grade w30) but couldnt find it after
looking for a while. all they had at the gas station was w20 grade for
diesel and reg gas motors. whats the difference between the two and can
i use w20 grade.
thanks
~Bezalel