1972 dodge dart with oil light flicking

Green1:

Oil is oil, is oil ,is oil. Straight weight? Wonder why engine builders like it. Wonder why it is recommended for inboard-outboards. Wonder why your lawnmower wants it.

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Is this a fresh built engine?

Is this a marine engine cooled by water intake never below 32 degrees, generally operated in waters 50 degrees and above?

Is this a fresh built engine on first start for break in, where oil will be drained in twenty minutes, and replaced with fresh multi grade?

Is this a small displacement air cooled, 3.5 hp. constant rpm engine with splash lubrication?

Oil is oil?

No, no, no, no, and no.

Just for the record, the last lawn mower and snow blower I purchased in 2010 recommended 10W30 & 5W20 weight oil.

A 1972 engine is not a pre fifties babit engine with huge bearing tolerances, which use to require single grade oil.

Reading list:
http://www.nordicgroup.us/oil.htm#How Sludge is Prevented