I switched oil from 30w to 15w 40 Delo (diesel rated), per the discussions here and in TW magazine,in my '64 Daytona 259. I noticed a slight improvement in oil mileage, but I am really sold now that I switched out the oil in my Ford 9n tractor!
I ran straight 30w oil, and several days ago mowed 1/2 of my neighbor's pasture (3' tall grass/weeds)using a 5' mower. This really works that high mileage Ford 4cyl. pretty hard. Anyway, yesterday I finished the job after switching to Delo 15w-40, and the oil pressure actually stayed 5-8 lbs. higher, and I used very little oil, compared to approx. 1/2 quart before!
To me, this is a good enough test to continue using the diesel rated oils in my Studes, regardless of the sightly higher cost!
I ran straight 30w oil, and several days ago mowed 1/2 of my neighbor's pasture (3' tall grass/weeds)using a 5' mower. This really works that high mileage Ford 4cyl. pretty hard. Anyway, yesterday I finished the job after switching to Delo 15w-40, and the oil pressure actually stayed 5-8 lbs. higher, and I used very little oil, compared to approx. 1/2 quart before!
To me, this is a good enough test to continue using the diesel rated oils in my Studes, regardless of the sightly higher cost!