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..
I used Rotella 15W40 in my Chris-Craft 454s in my 381 Catalina without issue. For years Crusader recommended 15W40 for their GM V8s based engines and Mercury specifies their own brand 25W40 for the MerCruiser GM V8s. Read between the lines and a multi viscosity 40W high quality oil is what you want either way.
Hey Guys. We have a 1972 41' Commander. It was repowered quite awhile ago with maybe late 80's early 90's Mercruiser 454's (carbeurated) from a salvaged Searay. I don't have any history other than that. I've decided to go with Quicksilver 25W40 as I don't want to change the recipe...everything has been going good. However, I'm trying to determine if adding a zinc additive would be a good idea. I've talked to several people on this and gotten as many different opinions. I don't know if I have flat tappet cams or not....not sure how to determine that? So should I add a zinc additive? If so, which one and how much?
Hi Joe, This is Tom from D Dock at the Shore Club with the 69/35SC. A late 80s early 90s CBB would at the latest be a Mk V motor which would still have flat tappets. I have not seen a recent oil analysis on Quicksilver 25/40 and they don't publish their ZPPD levels. I would guess, since it is formulated for modern boat engines with catalytic converters, it is probably in the 800-900 ppm range. If you have been running it in your motors, I would probably send a sample to Blackstone labs for an analysis - then you would know for sure and the analysis would tell you if you have any other issues. It is a relatively inexpensive piece of mind.
Thanks Tom! I order the test kits this morning. We shall see...