So, yesterday evening I'm sitting in the garage waiting for the latest batch of wild thunderstorms to get finished (they've been spaced about perfectly - just as things dry out enough from the last ones to get some work done, along comes a new bunch ) and I get to looking at some oil jugs. One, Castrol Syntec 5w-50 is rated "CF". A jug of Rotella "T" 5w-40 has a CH-4 rating. So I start pondering - what advantage, if any, is there to using an oil with a '-4' rating in an earlier engine which only requires a CF, or CD, or one of the earlier rated oils? Do the '-4's' lubricate better? Handle soot and crud better?
/ What Real Difference does the Oil's Ratings Make?
The number 4 designates it is for a 4 stroke diesel engine, so don't use it in your old 2 stroke Detroit. As for the API letter ratings the higher the letter the better. The most recent upgrade in diesel engine oils was the CJ-4. The CJ-4 oil spec represents the most drastic improvement in diesel engine oil standards ever. Here's a link to the API's own chart that describes the different spec's.
Some local digger has one in an old Louisville. Sounds like a 6-71 inine. A local farmer has a 6v71 in an excavator without mufflers !!!! When he cleared the field by my house you were up at 7:00 am on sunday morning !!!!
/ What Real Difference does the Oil's Ratings Make?
We run some old 4-71's in mobile generators and have some newer 6V92TA's in some big mobile Air conditioners. we run the dog piss out of them. the 4-71's just keep chuggin away with 12,000+ hours but the 6V92's we have are only about 10 years old and <3,000 hrs and they are wore out. not too happy with them.
) and I get to looking at some oil jugs. One, Castrol Syntec 5w-50 is rated "CF". A jug of Rotella "T" 5w-40 has a CH-4 rating. So I start pondering - what advantage, if any, is there to using an oil with a '-4' rating in an earlier engine which only requires a CF, or CD, or one of the earlier rated oils? Do the '-4's' lubricate better? Handle soot and crud better? 
