I have a 1987 Mercruiser 350 in my 23 ft ski boat and I am thinking about using Mobil 1 0w-40fs as I have it in all my older Toyotas and seems like a great oil overall. Would this be a good choice with enough ZDDP etc for this application?
Mobil 1 0w-40fs flat tappet mercruiser 350
- Thread starter AzFireGuy79
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M1 FS Euro 0W-40 does have higher amounts of ZDDP than typical API oils, about 900-1000 Zn/P. If this is a stock camshaft with stock rocker ratio, and stock springs, you'll be fine. Upgraded springs and rockers, and even some mild aftermarket cams, would also likely be fine. If the cam is more radical with high lobe intensity and high spring pressure, then I'd want an oil with more ZDDP.
By 1987 Chevy had the cam problems sorted out. As long as it's a stock build any decent oil will work fine
mercruiser specs a 25W-40 grade (Basically similar to a mono-grade 40) for those engines.
Id run a 15w-40 HDEO in it.
Id run a 15w-40 HDEO in it.
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0w-40 is my favorite 30 grade. I'd wager it would work but it is on the thin side, especially if OE is a thicker, or possibly a more shear stable/hths 25w40
I'd consider Mobil1 15w50 or maybe the motorcycle racing 4t 10w40, and also need answers on the build.
Another option is to thicken the 0w40 with some V-twin 20w50. A quart or 2 will add a little z/p/s and some visc
I'd consider Mobil1 15w50 or maybe the motorcycle racing 4t 10w40, and also need answers on the build.
Another option is to thicken the 0w40 with some V-twin 20w50. A quart or 2 will add a little z/p/s and some visc
Though M1 FS 0W-40 is formulated on the edge of the 30/40 grade boundary, and often shears out of grade slightly, it is actually quite stout for a common shelf oil. I'd trust it before I would any common conventional or syn-blend 25W-40.
You have to think, FC-W is a rather pathetic spec. It allows up to 50 ml of foam with 10 minutes of settle time, the minimum HTHS is just 3.3 cP, an SAE 40 can shear by 30% and still pass, and allows up to 22% Noack volatility. The only thing somewhat stringent about it is the saltwater rust prevention test which I don't think matters much to the OP living in Arizona.
You have to think, FC-W is a rather pathetic spec. It allows up to 50 ml of foam with 10 minutes of settle time, the minimum HTHS is just 3.3 cP, an SAE 40 can shear by 30% and still pass, and allows up to 22% Noack volatility. The only thing somewhat stringent about it is the saltwater rust prevention test which I don't think matters much to the OP living in Arizona.
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Sae 25w40 minimum hths is 3.7
Mercruiser labels their 25w40 as a synth blend, so I doubt its the worse oil out there. I've also never seen a problem with merc fluids... motor oils, gear oils, and 2-stroker oils. All seem to work extremely well around here.
Mercruiser labels their 25w40 as a synth blend, so I doubt its the worse oil out there. I've also never seen a problem with merc fluids... motor oils, gear oils, and 2-stroker oils. All seem to work extremely well around here.
I agree 100%. I have never run the crappy mercruiser 25w-40 in any marine motors(I’ve built quite a few including a 700hp BBC). A very outdated recommendation IMO. Boat in question is stored inside and on sees lake duty here in Arizona. Has freshwater cooling.
For those who asked about the build it’s a Mercruiser 350 with a Dennis Moore (Moore performance marine( custom flat tappet cam, factory gm lifters, new gm Vortec heads, Vortec intake, Holley marine carb and stainless Marine manifold system/thru hull. Boat is a 1987 Mirage Intruder 23ft with mahogany swim platform and built alpha one out drive. She is alot of fun! Appreciate all the input!
Run Motul 8100 5w40 in the family's 1995 flat tappet 351 boat these days...along with a Purolator Boss oil filter. It seems to maintain the oil pressure best at idle. Mobil One 0w40 was used for eons before that, (and Rotella 15w40 before that), but probaby 8 years ago they switched the formulation and it seemed to have slightly less oil pressure than it did before. I arrived at the Motul, primarily because it was 'thick' cSt at 100C, comes in 5 quart containers, and supposedly it's a really truly synthetic base. If Rotella 5w40 came in 5 quart containers, it'd probably have that!
I used to run 15w40 in my VP 305ci. If I still owned it, it would have either Delo or 1300 in the sump. Not that I have anything against running 0w40 in there, I just have more HDEO stockpiled.
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I'm a HUGE fan of M1 0W-40 and have used it in a ton of older engines for the same reasons as you. However, I'm running Delvac 1 5W-40 in our 351W GT40 due to it being a bit heavier and PCM spec'ing a similar viscosity to Mercruiser, which is a heavier xW-40. I don't need the added phosphorous, since the engine is roller.
I think many use a 15W40 gas engine rated oil.
Most people put less than 50 hours a summer on their boat engine so they don't really wear out the oil with respect to TBN or viscosity.
Most people put less than 50 hours a summer on their boat engine so they don't really wear out the oil with respect to TBN or viscosity.
Stock valve springs? Is the cam already broken in? One would think in a marine application is not too radical, but how intense? (what is the advertised to .050 relationship)
Chevy started using roller tappets in 1987. Would that not be the same for the Chevy - Mercruiser 350 Chevy engine. Maybe I’ve missed something. If that’s truly the case use whatever will pour in it. If it’s still flat tappet I’d go with a healthier dose of zinc - oil.
I use the M1 0w-40 in many engines similar to the OP’s (vintage Shelby’s and Cobra’s, e-type Jags, Triumphs, Sting Rays, Galaxies, etc). As well as more modern engines in Fords and Jaguars, LR’s, etc.
It would be a good choice. I don’t think the M-1 15w-50 will offer many (or any) advantages.
Z
It would be a good choice. I don’t think the M-1 15w-50 will offer many (or any) advantages.
Z
Mobil 1 15w50
Mercruiser actually didnt offer roller small blocks until the later 90’s. The 87 block has the bosses to covert to roller but my engine is a factory flat tappet black motor.
There was never a roller Windsor used in marine engines. I’ve been inside several GT40 PCMs myself. The blocks were roller capable but ran flat tappets (like the 351 in the lightning truck).
I have the same engine albeit a bit older in our Century Resorter and I run VR1 20w-50, a conventional as I run a mix of unleaded and leaded aviation fuels. If I didn't run a leaded fuel (synthetics don't, or at least didn't suspend lead deposits), I'd use M1 15w-50 or Delvac 5w-40.