I have seen a product at AutoZone called Slick 50, which claims to do the same thing. It's supposed to cling to metal parts better when the engine is at rest so it doesn't get so badly hammered at startup.
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It is NOT a 25% change. Don't believe there is any percentage relationship between various oil weight ratings.
Oil viscosity changes with temperature. For straight weight oil each weight rating has its own curve visc Vs temp. With multi-visc oils the additives change the curve so they thin out with temp much less than straight weight oil, flatter curve. For something like 10-40, a thin base oil that has the same visc as 10 weight at the cold temp measurement point will thin out to where it is the same visc as 40 weight at the upper measurement point. (Can't remember what the temperatures are at the measurement points.)
Mickey
Right, so if it is really cold you want a number lower than 10, or if it is really hot you want a number higher than 20 or 30. Like say 5w30 for winter and 10w40 for summer.
We have hot summers and cold winters so I run 10w40 in the summer and 5w30 in the winter.
Apparently MoS2 is used in assembly lube, and may be present in high concentration in 5W-20 motor oils, as well as in gear lubes. What I gather is that the sulfur is corrosive to copper parts. I'm not sure how much copper/brass/bronze is exposed to motor oil though.
I would stay far, far away from supposed engine treatments from Slick
50, Duralube, or any number of snake oil vendors. BTW - Slick 50 was bought out by Quaker State, and is now part of Sopus (Pennzoil/QS/Shell).Check out the 1997 settlement of FTC complaints against Slick 50:
They made tons of misrepresentations about the effectiveness of regular motor oil regarding startup protection. The anti-wear additives in most motor oils actually form somewhat of a protective layer during startup. They've also never proved that Slick 50 (PTFE) actually bonds to moving engine parts. About the only application I can see for PTFE as a lubricant is in a grease or spray lube. They no longer make the claims, but a lot of people will likely buy it based on their previous claims.
I tried Slick 50 once, and the only thing I noticed was that there was some hard, brownish crud stuck to the filler cap and the threads of the valve cover.
I've never used any. As far as optimum starting protection, I use a motor oil with a temperature range suited to my climate zone. My Subie actually starts with fewer cranks than my Jeep did. That thing could crank for a solid 7 seconds before ignition. I've logged my Subie ~2 seconds of cranking.
Well, head gaskets are copper, aren't they? I guess they only touch oil "edge on" in the various passages through the gasket from block to head.
Except that 40-weight is *heavier/thicker/more viscous, than 10-weight.
Viscosity increases numerically, with lubricating oils.
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