Logic would dictate that, but there seems to be more going on with the way different oils of the same viscosity behave. I really don't have the answer for it. I used to think oil is oil at one point , but that is no longer the case. What's needed here is a fluid dynamics expert to chime in and explain why for example Amsoil although is rated at the same viscosity as HD 360 20/50 seems to behave as a slighty thinner oil at normal operating temps even though it may not be thinner. The explanation I gave is something I whipped up on the spur of the moment.
Ron

 

Viscosity and film thickness/strength are seperate issues with oils. The trick, as I've been learning so far, is to find the balance. I use a 5-50 engine oil, and am often critisized for using something so low as a 5w. I've been researching this, and as I've mentioned to KBFXDLI, I know it works, just not WHY it works. I've put together a couple of pages on it, and sent it in to the expert who's been schooling me for final aproval. I don't want to mis-state anything in my conclusions. What I'm lacking to date is the realationship between viscosity, film thickness and heat (all three). The oil I'm using has a film thickness of about 2X that of a dino oil, so even at a 5W, I'm getting adequate protection. That's why I suspect that the thickness is the key to the bleed down issue, amoung others. When I get this all together, I'll offer it up for consideration.
I'd only be guessing about Amsoil, but if they claim a 50W, then their oil MUST flow at the given test rate, at temperature. Film thickness/strength could easily vary some, but here again, I'm still waiting to find out how heat affects that thickness as the oil travels through it's various viscosities.
Frank

 

I broke my 95" build w/ H/d 20/50 and bike made all kinds of noise.. Went back to Mobil 1 syn. now my bike purrs again. My bike knows the better oil.. Steve