Mineral 20W-50 Vs Fully Syn 15W-50

[R.Bingham]

Here is some interesting reading straight from the horses mouth.

Using Mobil 1 15W-50 in Harley-Davidsons

As I said before there is absolutely no problem using Mobile 1 15W50 in the engines of big twin Harley's.

 

[glider]

Here is some interesting reading straight from the horses mouth.

Using Mobil 1 15W-50 in Harley-Davidsons

As I said before there is absolutely no problem using Mobile 1 15W50 in the engines of big twin Harley's.

Answer: As long as the primary and tranny are separate sumps and there is no concern for clutch performance, then Mobil 1 15W-50 can be used in a Harley.

Doesn't mention the use in the engine in there reply. I wonder how much testing Mobil has done on the clutch system in harleys to give an answer like that. I'll still stick with the 20/50 V Twin engine oil with the proper additives for the engine that is air cooled as opposed to water cooled as per manufacturer recommendation. I'm sure that HD has tested the different weights of oil with their bikes more than Mobil has and why they recommend the 20/50 for their engines with the exception of varying temps.
I also wouldn't use the 20/50 engine oil in the trans either like Mobil says here.

In actuality you can use any grade oil in any component but using the suggest oil weight that the manufacturer recommends is the way I go with this rather than a "he said she said" approach. I'm sure that 10/30 would even work in an air cooled engine (for a while) but that doesn't mean I'm going to use it either.