C5XTASY

Title pretty well says it. I've read so many opinions on this I'm not quite sure whether to use 5W-30, 10W-30, 0W-40, 10W-40, 15W-50, or whatever. Thanks for any responses and reasoning.
Ed

jimcork1

10w30 gives a little better protection than 5w30 and doesn't give much in low temp starting. I live where it is 95+ for 3 or months each year and with traffic congestion and high underhood temps I stay with 10w30. But that's just my $.02,, Mobile 1 of course. vettdvr

C5XTASY

Thanks. I know several of the tuners use heavier oils than 5W-30. I was just wondering why. I wasn't sure if that was somewhat because that's what they had grown up doing (i.e. using petroleum cased oils) or because even with the much greater protection afforded by synthetics, there is a significant advatage to the heavier weights.
Ed

vettenuts

I use German Castrol 0W-30. The first number is only an indication of low temp pumpability. The 30 weight viscosity "range" actually runs from 9.3 - 12.9 Cst. Mobil-1 is a 10 Cst oil at 100* C while German Castrol is 11.7 Cst (Numbers from memory). So, even though they are both 30 wt oils, the Castrol actually has more viscosity at temperature. Castrol also meets ACEA A3 specifications, the Mobil-1 5W-30 and 10W-30 do not but their 0W-40 does. This is not called for in the owner's manual, but this is also a very tough standard to meet. I also have done oil analysis on every change since I bought the car and have had it reviewed by Terry Dyson, the best analysis results have been with the German Castrol.

Now just to caveat everything, I am not knocking Mobil-1 or saying it will cause problems if you use it. But everything I have experienced and read seems to indicate the LS1 likes a little more viscosity than 10 Cst. Since German Castrol is the same price, I am using it until I can't find it anymore.

HRDTOPC54FUN

Interesting post.

For what it's worth, at the advice of my tuner Amsoil 10W-40 High Performance. H/C 435 rwhp.

cST @ 100c = 14.9
cST @ 40c = 90.5

I'm thinking I need to research this a little more myself.

C5XTASY

Karl,
I cleared out my PM inbox. Sorry about that.
Ed

AFBombdude

The GC Gold is also showing good results

Dirty Howie

I used mobil 5-30 even though many suggested going thicker when I did the H/C ....... my engine failed.

Now with new engine (402) I will do what my tuner (A&A) recommends and use 15-50


DH

Dan_the_C5_Man

Well, let's be fair; you had a sticking pressure relief valve in your oil pump; that's a far cry from "Mobil 1 caused my motor to blow".

TSDuke

AMSOIL 5w40

FKING1

Royal Purple 5W30 in my head/cam 2000 , over 3 years.

Fred

Dirty Howie

Well I really don't know what caused my oil pump to fail except that there was crap that caused it to stick......this might have been spun bearings or who knows.....and maybe thicker oil would have prevented it or not........all I really know is that engine is toast

I guess the 15-50 is now being recommended due to the 402 stroked short block not having the same tolerences. I think one needs to evaluate their engines age/oil consumption/warrantee considerations/ambient temps and if its going to see heavy performance/track use.


DH

Darkness

I use Mobil 1 15w-50 on my 408, I just dont like how thin the 5w-30 feel it in your fingers, the 15w-50 was much smother because of the the thicker feel to it.

WKMCD

I'm running Royal Purple 10-40 in my H/C engine. I may go lighter when the weather cools but I doubt it. It gives me about 4-5 more lbs of oil pressure. The higher compression makes more heat and I drive my car harder than most.

bcseitz

Royal Purple 5-30

C5XTASY

There certainly appears to be no particular pattern. I find that interesting and wonder if it's because of the improved synthetics nowadays, over the old petroleum based oils of the 60's and 70's. I'm thinking that, assuming like tolerances to a factory engine, most any good synthetic might work fine. Now, an engine with wider tolerances, such as boring may produce, may very well require a heavier oil, petroleum-based or synthetic.
Ed

6Speeder

When you do heads and cam you aren't changing any of the critical tolerances, i.e. bearings to crank or rods, piston rings to cylinder wall. Why would you change the viscosity of oil?

If you are putting together a looser tolerance race engine, sure, go thicker.

But with the fine, factory, tolerances, the 5W-30 synthetic will work better than a thicker oil. It will protect better at startup and still be the best choice at the elevated power levels because you are still running the stock crank, bearings, rods, pistons, pins, and rings.

BTW: I've been running heads/cam from Sep 2000, allways with Mobil 1, 5W-30.

John Shiels

I ran Mobil 1 for 1500 track miles of hard use. That consist of either full throttle or full brakes for 90% of the time. I had the oil tested and was told I could run it 2500 miles next time. I did go to heavier 20/50 now and the oil pressure may be a bit better. No testing yet. I don't run it in the winter and do have the Accusump to prelube it before start up. I think 10/30 is fine.

Idavette98

Alisyn 15-40W. Slightly higher oil pressure, cooler oil temps, and my crane gold's are quieter. Was running Mobile 1 10-30W.

Sigforty

15W-50 mobil here!! I am running a heads and cam setup that pushes out over 450 rwhp and 425 rwtq.