Posted by Ben on September 10, 19100 at 12:54:35:
In Reply to: Mobile 1 Weight Question posted by #1 Son on September 10, 19100 at 10:47:07:
: K-Mart now has Mobile 1 at $3.79/qt. on sale, the cheapest around here. I went to pick up some and found that they only have 5W50 Wt. The truck calls for 5W30. What happens if I use 5W50 instead here in Houston where Summer temperature is, well, you know! Will someone please reply and explain? Thanks, guys.
: #1 Son
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First, I'm not a chemist, these just from my street education & opinion on the subject.
The weight numbers in relationship to lubrication oil tells us the "thickness" of the oil.
First number is the thickness at ambient and the second number when hot. There must be ranges listed on some specification chart, but I'm not aware of it right now.
You want lower first number to allow the engine to crank over with less drag from the oil. You want a reasonable higher second number so that the oil will have enough film strength when hot. *BUT* if the number is too high and the engine is in good shape, it will be *TOO* thick and may build up too high a pressure, which *WILL* cause harm to the engine (usually blow out some of the gaskets...I've done that on two engines).
#1 remember that your Sub is relatively new so going to a 50wt engine oil is not recommended. Higher weight oils can prolong a worn engine a while.
We've all heard/seen/etc some racer using 50wt oil and it works for them, as they are running at much higher engine temps, which requires a higher weight oil.
Higher weight oil also increases the drag on the engine and will cause additional wear (it takes more HP to do the same amount of work) and lowers MPG.
-Ben