Oill Grades and additives
I have an Atomic 4 (1977) and usually use regular 10W30 automotive oil. I was advised recently that being an older engine I should use an oil with some of the additives present (eg: zinc), meaning an API of SL or lower (the "ell"). Most regular oils I see are SM or SN I think because of the effect of the additives on catalytic converts. I see many motorcycle oils (4 stroke) with SF or SG so I wonder what anyone here thinks about adding a few quarts of this to the crankcase? Also whether mixing 10W30 with something like 10W40 or other grades is ok?
Thank you very much and sorry for deviating from the topic of this thread