I think the new rating for four stroke outboards is the FC-W which replaces all the other SAE grades. I would run any brand that had the FC-W rating . Not sure auto oil has all the additives the FC-W has. Just another $.02
http://www.bobistheoilguy.com/cms/
Below is from Yamaha:
Yamalube® 4-M FC-W® (SAE 10W-30)
4-Stroke Engine Oil For Outboard Motors:
Re-formulated to provide outstanding protection for all four-stroke outboards.
World Leading Lubrication:
This improved formula is designed to provide extra protection during the critical cold-start period, as well as during the extended operation under heavy load that four-stroke outboards so often face.
Rust, Corrosion, and Deposit Protection:
The additive package is formulated to fight corrosion, varnish, and wear for longer engine life.
Boat owners wanting the best protection for their four-stroke outboard should look for the NMMA FC-W® rating. With FC-W®, the protection gains are:
Far superior rust and corrosion protection, thanks to additives not available in today's passenger car oils.
High levels of bearing protection, far more than in passenger car oils.
High resistance to foaming under high engine speeds, foaming that can break down the oil's ability to provide lubricity.
Superior lubrication even when fuel dilution potential is present. This is particularly important when boating in cold water under low-speed trolling conditions.
Designed and tested by the marine industry for the marine industry.