I'm lazy about doing a UOA so I have no scientific backup other than sound wise, the QSUD has the slight edge. When I ran Amsoil 0w30, it was with a Wix XP filter. That filter in my opinion was a game changer as I started the OC with an Amsoil filter and didn't like the start up noise I heard. Changed to the XP, major improvement. The guys at BITOG hate on that filter big time due to its efficiency rating. That made me nervous so this OC I have an Ultra installed.
My guess is the flow of the XP is simply better due to its low efficiency. That being said, how much efficiency do you need?
Buddy , I'm in the same boat as you are my friend , I've only 1ea uoa under my belt with my oil of choice ( which gets HAMMERED ) here on a regular basis ?
I'm mainly going off of feel and sound as well .
For MY RAM 5.7L , it sure Like's the Redline oil , others not so much .
I've never bashed on their oil to my knowledge ? If I have I'm sure someone will chime in with a copied post of mine .... I would congratulate them .
Thing is with Blackstone Lab saying I should exceed 10,000 miles with Redline oil then everyone crying about the added cost just shouldn't imo , it cost me $101.00 filter and oil to do my last oil change , that's $50.50 each 5k , most people are scared to death to go beyond grandpa's 3k RULE much less 5k and even fewer would extend to 10k + like me and many others based on lab results.
I do max of 2ea oci a year and I feel with what REDLINE OILS bring to the table , I'm in better shape than anyone getting it done @ the dealer with their bulk oil out of date , full of condensation , mixed with whatever the 10$ per hr guy said ( uuhh yeh put that in that 500 gal container dude ) .
You never know what your getting ( Quality wise ) at the dealer or oil change shop .
I suggest everyone pours their own .
I've worked @ quick oil Chang shops ! 30 yrs ago ... Wow ! I'd never let them or the dealer change my oil again , especially after what I delt with at a local dealer of mine .
well , I'm stepping off my soap box now ..... let the Redline bashing begin