Best oil wieght for high mile engine

[pearsont74]

I am sure this subject has been beat to death but I want to get suggestions as im doing a full oil change and tune up this weekend.
What weight should I use on a high mile engine? also should I go with synthetic??

[Wyley87]

what year, make, model are we talking about here? how many miles on engine? any oil leaks

[pearsont74]

1996 GMC c1500 5.7 Vortec engine Auto with bout 100,000 mile ( i know its not as high as some LOL) no oil leaks (thank god)

[Wyley87]

have you always used conventional? i ask because in my experience that if you go with a full synthetic they can clean the junk from in between your seals and cause leaks. But if you are comfortable you wont have any leaks full synthetic should be ok. As for wieght synthetic only goes up to 10w-30 unless you get amsoil.

I use Mobil 1 Full synthetic with a Mobil 1 extended performance filter.

[pearsont74]

I have read about that...I havent had a chance to look but I can bet its reg oil and not full synthetic so not sure if i wanta risk a leak with switching. Thanks...that answered my question, might as well go reg. I know my dad has always used 10w-30 as well

[Wyley87]

no problem I have new engine with less than 25,000 on it. First oil change was at 600 miles after putting it in with conventional. After that its always had full synthetic. But since your going to use conventional and live in Florida I'd use 10w40.

[BernieB]

Originally Posted by Wyley87

no problem I have new engine with less than 25,000 on it. First oil change was at 600 miles after putting it in with conventional. After that its always had full synthetic. But since your going to use conventional and live in Florida I'd use 10w40.

I wouldn't go as high as a 40 weight in that engine, even in Florida. 10W-30, yeah, I could see that, but only the very southern tip of Florida has temps during the winter that stay high enough to justify a 40 weight. Unless you live down in the Keys I'd stick with 5W-30 or 10W-30.

[Wyley87]

Well GM recommend 5w30 for my engine but i live in Texas so i use 10w30. I heard that if i use 5w30 i can get better gas mileage but im averaging 17 now. Thoughts?

[Crmzendrgone]

Well to add more info than needed YOU SHOULD USE WHATEVER THE CAR MANUFACTURER RECOMMENDS at least on NEW engines cause with all this Variable Valve Timing and Variable Cam Timing and all, they use the oil to control a lot of it and if it is to thick than it can not perform as designed. Yours being a 97 though I would only recommend 10w30 but me I in the summer run 10w40 but I live in AZ and I have much higher miles so I want a little bit more protection and better sealing of the rings I say that cause the older the engine the more wear there is, smell what I am stepping in. But I do notice that the engine runs a little more smooth or just a little quicker on Accel. with the thinner weight.

[Wyley87]

you know something. i just thought about this here in texas the lowest temp i can remember was 17*F so i think i'll be ok with 10w30. ive never had any problems with it except when i ran out last summer when my rear main was leaking but thats another story.