Can 15W-40 Rotella T oil be used in 8.1 gas engine

M

Markd52

New Member
May 6, 2015
10
Wildwood, New Jersey
Boat Info
2002 380 Sundancer
Engines
Twin 496 (8.1) EFI Horizon inboards with V-Drives
I have been advised that 15W-40 Rotella T diesel oil can be used in a 8.1 gas engine. Has anyone heard anything on this topic.
 
For 9 seasons I used 15w40 in my 1989 7.4s, in spite of Merc's recommendation. Since buying this boat in 2013, I have been a good boy and followed Merc's recommendation of 25w40. I'm probably spending almost double per gallon but I'm doing it myself so there's no labor charges. Curious what others here will say about 15w40 in the 8.1.
 
I used 15W-40 Rotella before in some of my older engines 5.7 carbs... and it was fine... These are new engines and still under warrantee so i use what they call for... The 25-40, Spent so much money on this thing why cheap out on the oil....
 
In the grand scheme of things it's not that much more money. But I wonder why Mercruiser engines are the only ones on earth that call for 25w40. Maybe b/c they (and Sierra) are the only ones that sell 25w40 oil ??

Quick glance at Crusader's engine manual for the 2010 8.1 (and for that matter, all of the gasoline engines they sell) rec 15w40 for temps above 50*F and 5w30 for temps below 50*.

I will continue with the 25w40 but I'd like an explanation as to why I must.
 
Any major brand 15w40 is a good choice for that motor, with the T4 or T5 15w40 Rotella being a very good choice.

The new Merc oil is catalyst compatible, which means they must limit the Zinc and Phosphorous additives in it. Because of that, it is actually not as stout of an oil as the Rotella. Zn and Ph are high pressure boundary layer protection additives, and limiting them is not a great thing. I would choose the Rotella every day over the Merc oil.
 
Can't sea any problem with using the Rotella 15w/40. I've switched to aussie blended Penrite Racing 15w/50 and no longer have to top up from time to time during the season compared to when I was using the Merc 25w/40. As a plus its loaded with Zinc and Phos, contains no viscosity modifiers and claims to be shear free. Being a "light" 50, oil pressure is also similar to the 25w/40.
 
FYI, Mystic makes a synthetic blend 25w40. Its a Citgo product. Midland hardware website and the shipping isnt bad. You can buy it by the case(12 quarts) or gal jug. I had 3 quarts leftover from last fall so I ordered 2 gallons. $47 delivered. I think the case was $62 last year. No problems with it. My efis didnt burn any in 44 hours this season. I ran Amsoil in the past but it was over $110 a case.
 
I ordered from Midland last year - good deal.
 
Another Rotella 15w-40 user in my 7.4s for the last 10 years. The stuff was made for the harsh environments diesel engines create, so plugging along in a gasser isn't an issue.
 
Siboatguy said:
I used 15W-40 Rotella before in some of my older engines 5.7 carbs... and it was fine... These are new engines and still under warrantee so i use what they call for... The 25-40, Spent so much money on this thing why cheap out on the oil....
Click to expand...

That’s what I did in my old boat. Rotella is great. I only switched to the Merc oil when I repowered it because of the warranty.
 
I use Rotella T-6 in my Honda Goldwing. A lot of other Goldwing owners have used it for and have logged over 100K on their bikes. Check the ratings for the oil and if it meets your engine specs, than use it.
 
My new engines actually recommend Rotella 15/40. I've used it for 20 years in all my diesel trucks and off road equipment with no issues.
IMO it is a great oil
 
It is fine for gasoline vehicles that do not have catalytic converters. They left the zn and ph in it so it does not meet API SN as a result. It is a very good oil and great for marine engines without catalysts.
 
It is fine for gasoline vehicles that do not have catalytic converters. They left the zn and ph in it so it does not meet API SN as a result. It is a very good oil and great for marine engines without catalysts.
 
I have never seen the wrong oil hurt anything, but no oil, that's another story!
 
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