Oil choice in Volvo's

[NWpilot]

I recently purchased a 1979 Tolly with Volvo TMD40A engines with about 1600 hours on them. The owner's manual says to use 20W-30W oil at 50 deg F and up and 10W below that temp. The previous owner left a few containers of Rotella T 15W-40W on board, so I assume that was what he was using. Does anyone have an opinion or experience with running oils other than advised by the manufacturer?
Part of my thinking is that oils have changed considerably since 1979 and maybe the 15W-40W is a better choice. I am a synthetic oil fan but without any knowledge, I'm afraid of running it in them.

p.s. I live in Portland , Oregon so the temps here are not extreme and I probably won't make many runs with temps below 40 deg.

 

[RCook]

I used Delo 15-40 in my 1998 Volvo KAD44P, a little more advanced engine in their 40 series, for 18 years and 6500 hours cruising mostly on the Inside Passage. Worked fine.

 

[obthomas]

Right or wrong I run 15W40 Rotella in my TAMD40Bs. I do not go synthetic because I do not put enough hours on the engines between yearly oil changes to make it economical.

 

[Alaskan Sea-Duction]

I use Valvoline or Castrol 15-40 in my stuff. NAPA filters

 

[C lectric]

1976 Cummins V555M with 7,000 hrs approx. using 15/40 for the last 25 - 30 years. Good oil tests since I started about 1990.

I will make a plug for oil testing as it warned my of a building fuel in the oil problem long before any signs had shown up.

 

[Nomad Willy]

NWpilot,
Perhaps you could go to a place where they sell Volvo marine engines and dig up what the engine manufacturer recommends for engines that have out-dated specifications. The best recommendation will come from the engine manufacturer.

 

[ancora]

I've been using Delo 15-40 from Costco in my TMD40s for over twenty years.

 

[Ski in NC]

That engine has a sea water oil cooler, so cold-ish PNW water will keep oil temps pretty low. I'd probably use Rotella T4 10w-30. 15w40 is fine too, but probably a bit thicker than needed at the oil temps you will see. You can shoot the filter with an IR gun and see what oil temp you have.

Nothing really better with Rotella, all modern name-brand oils are fine, and way better than anything available in 1979. I just use Rotella as it is available anywhere and reasonably priced.

 

[koliver]

My boat came to me with TMD40s
I repowered to TAMD41s 2500 hrs ago
I use 15-40. over 4000 hrs so far and counting.
When I had to buy at the VP Dealer, all I could get was 15-40.

 

[NWpilot]

Thanks everyone. I received plenty of confirmation on the 15W-40W oil and some extra things to think about. I'm on my way to learning about diesels.