which kind?

[yaigottagmc]

I have a 99 sierra with a 4.8 (its my first truck and the first time to change the oil in it) the manul says to use either 5w-30 or 10w-30 i know climate does have to do with it i live in texas and today it hit 100 degrees and yesterday (Easter) it hit 95 degrees. So which would yall use?


Oh ya i bought a case of 10w-30 last night not knowing it said "prefered" next to the 5w-30 in the manul, but will i be fine using the 10w-30?

[gmtech]

Thats all we use in the dealer 10w30 and thats all I use and in texas thats what I would use so you did good

[bradrhale]

for texas, 10- 30 is just right, i remember that you have been looking at some modifications but until you do something drastic to your ride, i would stick with what you got.

[project88]

10w30 and 5w30 when both heated have the same consistancy. But where the 10 and 5 comes in is in the consistancy on startup, one is a little thicker than the other, in colder climates, 5w30 is recommended because it flows better when cold, however in texas 10w30 is good. Most garages buy 10w30 in huge amounts because they can get it cheaper and also 10w30 works well in any car. In high performance race engines, there have been reports where 5w30 oil is not good for start up, where 10w30 is thicker and protects the cylinder walls on start up. But thats high performance, (and as far as i know not proven scientifically) not most of us

[yaigottagmc]

THANKS for the help