Whats the thickest oil i can run 6.2L [Archive] - Diesel Place : Chevrolet and GMC Diesel Truck Forums

: Whats the thickest oil i can run 6.2L


jeffyboy
08-09-2010, 09:38 AM
I have an old 85 6.2L chev truck and recently it developed a slow oil leak coming from what i can see as the rear seal, not 100% sure thou. It loses a litre every 2 weeks er so. It didnt do this until I started running 15w50 rotellla. The previous owner ran crappy cheap oil and long intervals between changes. So i figure the oil got so thick/cruddy it didnt leak LOL. Whats the thickest/heavest oil I can run. I figure it`ll slow the oil leak so Im not changing it filling it up as much. This is only a temp fix for now until i can pull the motor an put new seals in i just dont have the time rite now to do it. Thanks in advance.

Diaric
08-09-2010, 01:39 PM
15/40 is the standard oil. not sure how 15/50 will affect it. if you've developed a rear main leak, check the CDR valve. excess crankcase pressure can make the seals leak

http://www.dieselplace.com/forum/showthread.php?t=11637

JLanzino
08-09-2010, 02:34 PM
Sae 30

zetan
08-09-2010, 03:41 PM
+1 CDR valve

jeffyboy
08-09-2010, 04:59 PM
Is there a way to test the valve? Ive heard a few ppl remove it should I do that or is it worth it?

zetan
08-09-2010, 05:52 PM
Do not remove it. It keeps a vacuum on the crank case preventing oil leaks caused by pressure buildup.

You can test the valve with a manometer to mesure the vacuum in the crank case.
Process described here
http://flashoffroad.com/Diesel/CDR/cdrvalve.htm

smackzed
08-09-2010, 08:58 PM
Cdr Cdr Cdr

Fred482`
08-10-2010, 11:57 AM
Recommended oils are 30 or 15-40 diesel rated, according to the '85 service manual.

4320Diesel
08-10-2010, 03:50 PM
if you replace your rear main seal, replace it with a lip type synthetic seal. i put one in my truck after my factory rope one started leaking and it stopped the leak and seals so good i can run it without a CDR and i have no leaks from the rear main seal lol.

Diaric
08-10-2010, 04:10 PM
seals so good i can run it without a CDR and i have no leaks from the rear main seal lol.

don't be talking about running no CDR , or you'll have to give yourself a warning :chicken:

4320Diesel
08-10-2010, 04:13 PM
i was a mod longer than you! and stop trying to derail the thread! :p: anyways, unless all your seals are 110% and your CDR doesnt work anymore. leave it in place.

JLanzino
08-10-2010, 11:45 PM
Recommended oils are 30 or 15-40 diesel rated, according to the '85 service manual.

In The 91 Manual It Shows 10-30 Diesel, 15-40 Diesel & 30 For Recommended Oils

Mikes85
08-10-2010, 11:59 PM
The sun visor on my 85 with hd engine says 30 above 60 degrees. 10-30 below 0 to 60. Or 15w-40 through the whole range.

Also says oil change at 2500 miles for severe duty.
5000 miles for light duty.

JLanzino
08-11-2010, 12:03 AM
Sounds About Right

jeffyboy
08-13-2010, 06:32 PM
Thanks guys this place is great!Everyone is so hopefull. Ill replace the CDR and if that doesn`t work ill replace the seals once I get time before winter.

Livelli
08-13-2010, 07:07 PM
they can be cleaned too. If its not broken, but malfunctioning, save your money and clean it out.

countryboy90
08-13-2010, 08:25 PM
maybe just try changing oil brands. i know this is kinda different, but on our farm using allis chalmers tractors our tractors would leak rotella but once we switched oil brands it went away. but i would check your cdr first.

gmtgmt
08-15-2010, 10:43 AM
would it hurt to use 10-40?

4320Diesel
08-15-2010, 10:54 AM
it says in my owners manual that ALL WARRENTY IS VOID IF 10W-40 oil is used. beats me why though.