Trying to figure out which type of oil to run in older stuff has always confused me since API ratings have changed over 40 years. I have a set of Chris craft marine 454 engines and the original manual says to run SAE 30 or 10W-40 with an API SE. I see Volvo makes a 10W-40 that has an API SJ but I don’t know if that’s appropriate or not. I’ve heard of people running valvoline vr1 30 weight for the high zinc count in it. There’s obviously the people that run 15w40 diesel oil and merc 25W40 and apparently that works for them. I get all these numbers and letters in my head and then I get all sorts of confused so any help from what you guys have to say would be appreciated.
Thank you
-Grant Litynski
You can use SJ in an engine designed for SE, but not vice versa. SAE 30 might be hard to find, but 10W40 should be available. As for the zinc, if your 454s have flat tappet cams, get oil that has it or use an additive.
15W-40 diesel oil (or 5W-40 if you use the boat a lot in cold weather) would be my first choice for a marine big block. It's not the highest zinc oil out there, but it's got plenty for the relatively mild cams in stock flat tappet engines. My 454s have been running on either Rotella or Delo 15W-40 for years, originally the conventional version, then they got switched to synthetic blend because at some point it became cheaper and easier to find. Many of the diesel oils are dual rated for use in gas engines (the most current ratings would be CK-4 / SN) and pretty much any of them are good performing oils, so within the realm of diesel oils, I'd just get what's easy to find and at a good price and use it.
An xxW-40 is a suitable viscosity range for a 454 and there's no reason why a marine 454 is overly hard on oil, so realistically, anything in that viscosity range and with an appropriate amount of ZDDP for the flat tappet cam will do fine. If you want to know more than you ever dreamed about oil, do some searching on bobistheoilguy.com, there are people there that have done analysis on tons of different oils in different engines, etc. and a few actual oil chemists on the site as well.
With modern oils, outside of certain applications with very specific needs (like 2 stroke Detroits), there is no good reason to run a straight weight oil. The issues with multigrades shearing badly, etc. that people worried about 50 years ago aren't really a concern now in most cases.
I have been using Rotella 15W40 (1100-1200 ppm of ZDDP) in my CC454s. I like the multi-viscosity for the cold starts that we get in early spring (MI). I may switch to Driven GP-1 15W40 semi synthetic next oil change based on flat tappet testing by Lake Speed Jr..