Hello, everyone.
It's getting to be time to do an oil change on Number Seven. So, seeing as I don't know much about oil (aside from the fact that it's slippery and goes in the engine), I did a forum search and asked around. After reading the various threads (and there are lots), talking to my mechanic, and talking to my FLAPS guy, I am left with the following conclusions:
1) Multigrade oils are easier to pour when cold, and pump easier in a cold engine -- which reduces engine wear.
2) Multigrade oils never actually physically thicken to what a single weight would be, which can be hard on your engine once it warms up a bit.
3) Using an oil that is too thin is bad -- it pumps easy when it's cold, but it is too thin to lubricate well.
4) Using an oil that is too thick is bad -- it doesn't pump easy until it warms up, at which point it lubricates well enough.
5) The shop manual says to use SAE 20 oil when the external temp is 32° - 90° F. SAE 30 is what I should be using, should I ever run the truck heavily in weather that is over 90° F, because it's thicker and will lubricate better.
6) SAE 20 is "really thin".
7) The winter rating on multigrade oils only comes in when the temp is 0° C or below, which it never actually gets to up here except on rare occasions when I call in and stay home.
8) It seems that most of you guys that use single grade oils use SAE 30, but also, you aren't in the "Frozen North", where it only gets above 90° F about 30-60 days a year.
9) Don't use synthetic if you've been using regular oil for any amount of time.
10) Most new oil won't work in anything that I own. It has been reformulated to not gunk up in the dinky little engines coming to us from the east. Anything with a steel/iron cam should not use anything with that little "For use in gasoline engines" sticker/seal/graphic on the front of the bottle.
11) Most (if not all) of the oil at the FLAPS has that stupid little sticker/seal/graphic on it.
12) The oil with the sticker/seal/graphic would probably work fine with the addition of some sort of 3rd party anti-wear additive (which the FLAPS has)
13) Shell Rotella T is the way to go, because they still put that additive in there that keeps your camshaft from wearing out.
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Okay. Now that you have a fairly good idea as to what I've read/been told, here're my questions.
1) If SAE 20 is "really thin", why would the shop manual say to use it for most operating temps? Is it too thin? What was Chevy's reasoning?
2) If SAE 20 will work fine, but I cannot find any, is there a vendor that will sell me some Rotella T SAE 20 oil over the internet or by mail order?
3) If SAE 20 is unsuitable or unprocurable, will SAE 30 work fine? It's thicker, and doesn't pump as fast when it's cooler. Will this make a difference? Will this make a difference in the winter when I fire the old girl up periodically?
4) If SAE 30 won't work for me when it's colder out (I drive it April - October or November), then which multiweight oil should I get? I've seen some 20w50 kicked around, as well as 15w40. Will those multiweights be bad because they're thinner?
Any facts and opinions will be appreciated.
