Quote:
Originally Posted by thescreensavers
Hog wash, oil pressure will lower with temperature a 30wt oil will be thinner than 40wt at 230,270..pick any other hot temperature the 40wt will be thicker and thus higher oil pressure. Oil shearing is tested in an astm test called "ASTM D5481" HTHS values are usuallylisted on oils PDS . Dex 2 oils are 3.7+ range while dex1 being 3.0 range. higher hths the less the oil will loose it's viscosity with high temp high shear and return back to spec and not shear out of grade.
I would advise against what you have read but I'd like to take a look care to share a link?
I would follow GMs guidelines in respect to warranty and longevity.
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Here's the link.
https://540ratblog.wordpress.com/201...-test-ranking/
A long read, but definitely a lot of good info. I wasn't referring to oil pressure in the engine, but actually the psi value produced by the oil in terms of wear protection. I'm a huge advocate of trusting the engineers that built the car, but they often have to dumb things down for people who don't educate themselves like we do on forums. According to this guy 30wt oils have the best long term wear protection, you have to ensure it works for your application though ie high temps from track use.