SG rated diesel oil

[bchannell]

I was at Tractor's Supply today, and found Traveller 30st diesel oil, SG rated, and made by WPP, same as Super Tech oil. Looking at the specs I was wondering a couple of questions.
1) SG is a pretty old spec, how much does it differ from today's SN? Is it like SL and has more zinc and all the other good stuff, or is it worse by some measure?

2) How can diesel oils meet both SN and CJ4 specs? I mean diesels need higher zinc, and SN limits zinc. Is it because diesel oils are different weights and don't have to meet a certain spec for the S rating?

 

[bullwinkle]

1. SG is an obsolete gas spec, not a diesel spec. The Traveller straight 30 is only for old gas tractors, etc., or really old gas engine cars, possibly a power transmission application.

2. SN, in a 40 weight or higher, has a higher zinc (ZDDP) limit than 30 weight or lower. That's why a 15W40 may be dual rated SN/CJ-4.

 

[Ramblejam]

Originally Posted By: bchannell
2) How can diesel oils meet both SN and CJ4 specs?


https://www.infineum.com/media/80723/api-engine-oil-classifications.pdf

 

[bchannell]

It is a labelled Diesel rated oil, but also carries the SG rating. It is NOT the standard HD30 Traveller oil. My bad for not being more clear. I actually don't remember the diesel rating on it, just the gas rating.

 

[bchannell]

Rotella T5 10W30 is an SN rated diesel oil with more zddp than a 10W30 PCMO, SN oil of the same grade?? ~1200ppm opposed to ~850ppm respectively.

 

[bullwinkle]

Originally Posted By: bchannell
It is a labelled Diesel rated oil, but also carries the SG rating. It is NOT the standard HD30 Traveller oil. My bad for not being more clear. I actually don't remember the diesel rating on it, just the gas rating.

I'll have to look next time I'm in a TSC, I wouldn't think the spec would be CJ-4, more likely CF or CG-4. Last diesel engine I've seen recommend SAE 30 is my '93 6.2, although newer ones could probably run it.