The results are nearly linear with Viscosity ratings. The outliers show the better products and worse products. Example is the Redline 5/40 bucking the trend, this is a very good score for that weight. The Shell 15/50 is very weak in comparison it should come in right after the 20 wt products.
A mulitgrade oil is intended to increase viscosity with heat, the more viscosity the more shear strength. THis is a room temp test.
Tests should fall in the the following order in respect to protection at room temp or above freezing.
0wt - Worst
5wt
10wt
20wt - Best
Straight 30wt.
The thinest weights allow the car to start in very cold weather and protect the motor. That is the old school formula. While thin, it is thin enough to pump quickly and prevent damage. A 20wt oil in sub zero would not protect as well at start up, taking longer to pump to critical components.
Mfg tolerances, multi-valve motors, hydraulic chain tensioners, etc all play a role in the oil weight selection for the OEM. Take a base 4.6 32v Ford, it likes a 5w -X for tolerances but also needs it to get the chain tensioner to pump up fast and avoid a ticking noise at start-up. But throw a 20W in it and if you don't blow the filter off, it will make a ticking sound in very cool weather. Anti-drain back filters are also more popular as they keep oil in the can and can feed those hyd tensioners quicker. Spin a filter without it on a 24v Ford V-6 in cool weather and listen for the tick, tick tick.
As your car warms up your viscosity increases. IMO the test just proves that reving a cold motor is NOT smart. Always get the car up to temp before hammering on it. We have a 50wt vis, simply the most protection in any traditional oil. The 5w beginning number is for tolerances, again, do not rev a cold motor and you should have no issues.
I have no clue what this magazine was trying to prove. This is oil 101. It does not sound like the author understands the concept. He should have been able to predict the finishing order by Vis. If comparing a 10wt vs. a 10wt, then you have something to show.
Tpraceman lines it up perfectly... Just compare the starting vis to a simlar starting vis. the durablend is a stand out as the test results should double with the doubling of the vis.
I think Royal Purple is a good product, I even helped them get a start on the retail side, but I seriously wonder if someone did not sneek in some straight 40wt and 50wt for this test or heat it up. I see no other logical reason for the psi to be that high.
