Straight Weight Synthetic Oil (30 or 40 weight)

Strack

Veteran Member
Joined
May 10, 1999
Location
HAckensack, NJ USA
Does anyone know of a decent straight weight synthetic motor oil suitable for a marine application. Mercruiser recommends their 25W/40 mineral oil (CH-4 rated), but I'd prefer to go synthetic (against their advise)..
Sorry for placing this non TDI related posting here, but this forum is full of very knowledgable oil gurus!
 

car54

theGAME
Joined
Dec 5, 2000
Location
Woodbridge VA
TDI
2002 Jetta
more info... what type and year motor is it on your "marine application". you say mercuriser, so I'm guessing its gas. I use mormal 15w-40 shell Rotella-T in my boats. I have a mercruiser 170hp 4 cylinder (1983), and a wellcraft with dual 454's (1989). Marine engines are rudimentary car engines with no need for thin, ultra high quality oils (unless its new, Judging by factory spec, its not). A buddy of mine with a Wellcraft NovaII Spyder with dual 454's (same boat as mine) Used 5w-30 synthetic, he didnt develop enough oil pressure and burnt the top end of his motor up. If you use a synthetic, go with a top quality heavyweight, and watch your oil pressure. I would advise against using OEM oil, its the same stuff you buy off the walmart shelf, at a premium price.
 

TooSlick

Top Post Dawg
Joined
Dec 2, 1999
Location
Dixie
TDI
Audi 100S
Strack,

If this is a new motor ...I'd run it for 50 hours on petroleum oil and then switch to synthetic. The best Amsoil product for this would be their 15w-40 - the same stuff you sometimes use in your TDI.

If you want something off the shelf, I'd go with Mobil 1, 15w-50.

TooSlick
 

TooSlick

Top Post Dawg
Joined
Dec 2, 1999
Location
Dixie
TDI
Audi 100S
Strack,

Amsoil makes a straight 30wt PAO/Ester synthetic diesel oil (product code is ACD), in fact it was the first diesel oil they produced back in 1975.I generally recommend their 15w-40 Marine and diesel oil for these applications, however. My neighbor runs it in a 37' SeaRay, with twin 454 "Mercruiser" inboards. We did oil analysis of some after 125 hours (a full year) and it held up very well. The reason why they recommend a 25w-40 is for shear stability in a constant speed, high load application, BTW.

Please e-mail me offline if you have any other questions.

TooSlick

[ March 25, 2001: Message edited by: TooSlick ]
 

golfstream

Top Post Dawg
Joined
Jan 10, 2001
Location
Balmer, Hon
TDI
Golf, 2000, Black
Strack,

I also use Shell Rotella T 15W40 dino oil in my 1983 Perkins 6-cyl. diesel. Good choice for older marine engines.

Mel
 

Strack

Veteran Member
Joined
May 10, 1999
Location
HAckensack, NJ USA
Thanks Guys,

It's a new Bayliner Capri with a 3.0 liter gas Mercruiser engine. Mercruiser does not recommend synthetics for their engines, they sell their own brand (Quicksilver) of 25/40 mineral oil. They recommend using straight 30, 40 or 20/40 or 20/50 weights if their own spec oil is not available...

Interesting note, Merc's 25/40 oil does not use viscosity improvers and is CH-4 rated. But at $3.00@quart this is a pricey solution..
 
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