Rotella T CH-4, CG-4

[mjoekingz28]

While picking up parts at AAP I came across some old Rotella and decided to pick up a gallon. I really wasn't thinking, but did think it should do no harm.

Not in the donut, but underneath is says "exceeds engine requirements of API CH4, CG4, CF4, SJ, SH.

Now, I have a Saturn and it is an oil burner (1qt/1500-2500 miles) and am concerned it may do my cat and/or oxygen sensor harm. I am concerned because I read how SM goes the extra mile to keep the cat safe and maybe SJ doesn't. SJ is good for 2001 and previous and my car is a 98 so I should be good, but maybe the engine wasn't burning oil back when SJ was around.


Am I worrying over nothing or should I use it in the mower since my Sat uses so much oil?

 

[widman]

You will get a lot of opinions. Some of the Shell formulations of that era were magnesium or high magnesium instead of calcium. Those have high ash content and continued use gives high cam wear (documented by Komatsu).

Yes, it could hurt the converter, but not in one oil change period. I'd use it. the extra cleaning over a straight SM should be a help in the long run.

The real damage to the converters is the oil burning and the formulations that have the cheaper, more volatile phosphorous compounds.

 

[m37charlie]

Actually I believe Shell has used Ca salicylate detergent technology for many years. Regarding ash, 1 TBN unit = 190ppm Mg but requires ~300 ppm Ca. (atomic wt of Ca 1.6 times that of Mg)
That means 1 TBN unit of Mg is ~.08% ash whereas 1 TBN unit of Ca ~.096% ash. (Multiplier ppm to ash for Ca =3.4, for Mg 4.25) Therefore, per unit TBN, Mg detergents produce less ash than Ca based detergents.
Of course this has little to do with the OP's question. I agree the real risk to the convertor is oil burning and the P in the ZDDP from the burning.

Charlie