Schaeffer's 7000 vs. T5/6?

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Looking at doing some PM on an '89 Chevy G30-based RV (TBI 350) that a friend just acquired. I've been running Schaeffer's 7000 10w30 in my '85 GMC (454) for about the last 10,000 miles (first OCI was 6,400) and am very pleased - it seems to hold up exceptionally well in the big, old, flat-tappet engine. But to save a bit in materials and have a more common oil when it comes to make-up, I'd feel just as good about using Rotella T5 or T6, probably in a 10w30 or 5w40 weight - not so much from prior experience with that oil as by reputation and the opinion of the BITOG collective. Any opinions yay/nay on either?
 
For ease of purchase nothing wrong with a HDEO in 10w30 the CJ-4 formula has plenty of ZDDP for the camshaft. My 350 in my 76 K10 currently has Delvac 15w40 in it. No harm in running that either.
 
True, 15w40 won't hurt it. From hearing it cold start the engine sounds good and healthy (78K on the odo) and my truck was substantially more limber when I switched from 15w40 to 10w30 so I'd like to use 10/30 if the engine seems tight enough, upon further inspection, to allow it.
 
Originally Posted By: Alex_V
Why?


T5 is not a high zddp oil.
Neither is the latest version of T6.
Higher zddp in HDEO's are not necessarily best utilized because higher detergent content inhibits the effectiveness of the zddp.
Valvoline VR1 is a high zddp oil designed for gasoline engines.
And in general, GM recommended against 40 weights for their engines of 30 years ago.
 
Last edited:
This was Schaeffer 711 10w30 CJ-4




This was Mobil Delvac Extreme 10w30 CK-4 Yes, CK-4, not a typo.




And this was Schaeffer 9000 5w40 CJ-4




Currently have Schaeffer 15w40 CK-4 in the truck now and will know what it looks like when I do a UOA on it.
 
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