Theres nothing wrong with the mobil 1 15w50. I used it in my springer for over 30,000 miles and never a problem. Currently have over 10,000 miles on my road glide with it also. I think their 20w50 formulated for v-twins is more a marketing ploy to justify the extra $3.00 a quart over the 15w50...

 

just talked with a good friend and a local indy yesterday as I was picking up my filter and primary drain plug o ring. I told him I was using Mobil 1

he mentioned a rebuild he was doing and referenced the parts tank to prove his point.

They have a used fluid parts tank and a fresh fluid parts tank

All parts go into the used fluid first - then the fresh

The rebuild was due to a customer not happy with another shops head work and had less than 2000 miles on the fluids

the Mobil 1 was so sticky to the parts, it would barley come off after 30 min in the dirty tank and an hour in the clean tank

he was so convinced by what he saw, he immediately changed all the fluids out of all of his bikes (he has over a dozen)

 

I use the following in my '06 Road King Classic:

Motor - Mobil 1 20W50 synthetic
Primary - HD Formula + dyno
Trans - Mobil 1 75W90 synthetic
HD Chrome filter

I just finished changing my engine & primary with the temps in the garage running around 60 degrees F. Man was the 20W50 & Formula + pouring thick! It was like honey!

Edmo