New SM oils good for cats, bad for engines?
 

OK, I am just getting up to speed on this, so I am no expert, but it appears the new API SL oil standard has fewer anti-galling agents (Phosphorous and Zinc) which are good for metal-metal contact areas such as bushings, bearings, valve train, etc.

So basically, when Mobil 1 changed away from colored caps, they lowered our engine protection. Apparently it started before that back with the SJ-SL change, but the SM has taken almost all of these components out.

I am still researching this, but check out this thread and this link to start with.

Super Trucker... Can you get us a deal on some Diesel oil?

May have to go Red Line which is all the Stealth has had in it since I got it, though they don't appear to publish their numbers...

And if you can find any blue cap Mobil 1 anywhere, buy it.

Dean, Honestly, Costco has the best price on Chevron Delo 400, which is my favorite Diesel engine oil. Their price is usually even lower than the local distributor.

This is interesting though, I'm going to read up on it.

As far as I know Delo only comes in 15w40, 30w and 40w though. Might be kind of thick when it's cold, but should be OK during summer.