what is the diff between, Multi-Grade Oils, and Straight-Grade Oils?

[Faze2183]

im wantin to know what is better?

Multi-Grade Oils, and Straight-Grade Oils?

and whats the diff?

[joe92k1500]

Better depends on the situation. Straight grade oil ( like SAE30W) are not commonly used in cars. Reason being is that they do not flow well in colder weather resulting in oil not being distributed in the engine when cold ( ususally below 50F). Multi grade ( like 5W-30, 10W-40) flow much better in cold weather but retain their viscocity when the engine warms up. Oils that are rated at 5w-? will be good for below 0F temps. Using straight grade oil instead would be like frozen ice cream through a straw. If you live in a southern climate, 10w-? are usually fine.
For me I would go multi grade because you get the same protection but through a greater temperature range. Almost all manufacturers recommend multi-grade

[Faze2183]

is 10w30 pretty good for a san antonio tx. truck? my truck is a 1996 chevy k1500, with 170k miles, i change my oil every 5k miles because im running royal purple, and or would 10w40 be better?

and im also running a AmsOil SDF23 oil filter, and a magnetic drain plug i just added that resently.....

[broughy84]

10w40 with that high of mileage

[Faze2183]

and what about winter time?

[joe92k1500]

broughty84-

Why would you use 10W-40 just because the engine has 170k mi? My engine has 184kmi ('92 k1500 5.0L) and I use 5W-30 because I live in Wisconsin, and that is what GM recommends.

[broughy84]

i guess just personal preference.

[cc rider]

I found a site that has WAY more info on oils and such than anyone could ever hope for.

www.bobistheoilguy.com

TONS of great info on oils, gas, additives, cleaners, you name it.

c.