Harley Davidson recommends 20w-50 oil and possibly 60 wt if ambient temps are above 80F, according to their website FAQ page.

The oil manufacturers tout high viscosity oil for use in high mileage engines, but all that does is delay the inevitable rebuild.

Last edited by klhansen; 10/24/2025 6:21 AM.
Kevin
1951 Chevy 3100 work truck
Follow this saga in Project Journal
Photos
1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.