Oil Change

[Piledriver]

It's not _quite_ Government required, but it depends on how it's marketed.

Shell Rotella T6 I run is rated SM etc but is still 1400 PPM... 800 PPM is only required for the API "starburst" symbol.
Same for VR-1.

It's strictly a marketing thing, as in if marketing or engineering is running the company.

If it's labeled heavy duty or racing oil or 40+ weight there is absolutely no requirement to be at 800 ppm... although Castrol GTX (all grades) is ~800 ppm and is thus "Liquid Death" to flat tappet equipped engines.

You have to buy Castrols "expensive" Syntech oils to get flat tappet safe oil.
(and not all of those are sure to be safe)

This unannounced change in oil//policy is why I will never buy another Castrol product again. Ever.

Gasoline engine only oils can have the additive package changed on the whims of marketing.
"Commercial" (diesel) oils cannot, they require a hideously expensive re-certification for all the engine manufacturers requirements for virtually ANY change.

Commercial oils primary downside is the killer detergent and anti-foaming additive packages they must run.

[rockerarm]

I personally use the diesel rated oils. I broke in my engine with an easily available Shell Rotella 30wt. This was ok'd by the cam grinder, Web Cams. After a few thousand miles I changed to the Chevron Delo 15W-40 oil. I agree with piledriver that Castrol aint doing us any favors. Damn, I met a east coast traveler, here in Los Angeles, who had broken down, had a motor built up to a 1776 and engle 100 cam with scat lifters. Shop said to use Castrol gtx 20w-50! Tried to school him but I aint warranty'n this engine.
It is interesting to see that when the aftermarket crowd had determined the oils were at fault with all these flat and pitted parts, diesel oils were the savior! After a certain period of time many new boutique oils appeared to remedy this issue. One thing I read was that diesel oils were now taboo, stating these oils foamed up and had too much detergents! But, Chevron, Shell, Valvoline, Mobil, and others have these oils as dual rated.
Ya know, my opinion is if one has a daily driver car, which I have, and demand the easily available maintenance items I need, I'm gonna pursue that. As a tech, working on folks cars, on the side, I demand easily available maintenance parts/supplies. I'm in Los Angeles.
If one is shocked at the use of a diesel oil, motorcycle oils and the high mileage oils have the additives our flat tappet motors need.
If someone thinks diesel oil don't work in our mild engines, let me know. My bus was built about 4-5 years ago, driven daily, and at times thrashed around town and freeway.
Hope this helps, Bill.

[Piledriver]

Modern diesel oils have outstanding anti-foam packages, as common rail injector pumps really hate bubbles.
Probably ~equal to any racing oil in that regard.

The only (possible) legitimate reason not to use a modern diesel rated oil is they also have brutal detergent packages, which may slow down ZDDP building up that initial protective layer, so perhaps not ideal for break in.