[JimFB400HO]

Formulabruce, I think I would probably be fine with 10-30 like you mention and may have to go with it some day.

I do add ZDDPlus to the 30W to get the zinc and phosphorus back to the old levels. My '68's engine has never been rebuilt so I have to adjust the oil and gas to make up for the old cam and tappets and the original valves , seats and compression.

The straight 30W comes with a story: When I took my '68 (with the 400HO) into a dealer for warranty service in 1969, I mentioned the engine slightly "tapping" The service manager asked me what weight oil I was using. I told him 10w30. We got my owner's manual out and he pointed out a footnote to the recommended oils. I can't remember if the Service Manager underlined that in my book 52 years ago or if I did. Ever since then, (now with 183k on the odometer) I've used straight 30W in the summer. And, yes you are correct, the '68 Service Manual does not have that note.