oil for a marine 351w?

[Japanese]

Thank you for your vote of confidence here, I appreciate it.

You are welcome. You already got useful recommendarions on the first page by people who run the same engine and if not the same exact oil, it's at least the type (diesel) and viscosity.
If you have time and desire you can call Mobil and ask them how much zinc there is in the oil, if you think they changed the formula since 2021 (when are made the UOA from the link on my previous port).

 

[Zap1967]

Bearing clearances on the 351s are pretty tight as assembled. No need for a 20-50 but I do run vr1 20-50 in one I have. When the oil gets hot from extended WOT operation the pressure starts to get a little low for my taste (it’s probably just the 45 year old gauge).

Everything else ford wise gets 15-40. They aren’t hard on camshafts.

Big block Chevy on the other hand are know camshaft offenders. My main 454 drinks conventional VR1 and has 1200 hours on everything in the short block/cam and lifters. This one has a big oil cooler and gets ran to extremes. I had a used oil analysis done on it a while back after a hard 30 hour duty cycle. All wear came back as normal for universal averages. The oil had sheared down to a 40w but it did have some fuel dilution (likely a symptom of being carbureted and it needs to be worked very hard to get the oil up to 200+ with the big cooler).

 

[alarmguy]

if "high zinc" is needed, diesel oil is no longer ok.....there is much on this site and others about this...... out of the 5 choices I would go with VR1 or M1.

Yup. VR1 says it right on the container under the words "America's #1 Racing oil" if the image is blurry. designed for Push Rod and Flat Tappet Engines

 

[alarmguy]

I’m curious what the oat manufacturer calls for oil viscosity

 

[alarmguy]

Bearing clearances on the 351s are pretty tight as assembled. No need for a 20-50 but I do run vr1 20-50 in one I have. When the oil gets hot from extended WOT operation the pressure starts to get a little low for my taste (it’s probably just the 45 year old gauge). ….

I doubt it is the gauge.
Oil temperatures in a marine engine can easily exceed the temperatures of a normal automobile engine
The stress on a marine engine, pushing a log through water is for greater than in automobile engine rolling on four wheel wheels

 

[Japanese]

I’m curious what the oat manufacturer calls for oil viscosity

It looks like the OEM recommended oil is 5W-30. But for the older flat-tappet engines (prior 1993, like that in the boats) thicker oil with higher ZDDP content is desired.

 

[alarmguy]

It looks like the OEM recommended oil is 5W-30. But for the older flat-tappet engines (prior 1993, like that in the boats) thicker oil with higher ZDDP content is desired.

Wow, never thought it would be so low (the op hasn't stated the year)
I run 15/50 Mobil 1 in a 4cyl Volvo Penta (2008) this is the first change I did with it. Before that Mystik Semi Synthetic 15w50. At one time I think it called for a straight 30 but then was changed. I'll have to go back and look. I guess it's just me but nothing less than a 40 for me.

 

[OVERKILL]

Wow, never thought it would be so low (the op hasn't stated the year)
I run 15/50 Mobil 1 in a 4cyl Volvo Penta (2008) this is the first change I did with it. Before that Mystik Semi Synthetic 15w50. At one time I think it called for a straight 30 but then was changed. I'll have to go back and look. I guess it's just me but nothing less than a 40 for me.

Ours recommended 20W-40, but that was 1995, when oils were far lower quality. Newer engines do indeed recommend xW-30 grades, especially the GM LSx-based options.

 

[ammolab]

I've thought about VR1. It's not readily available at my local Walmart and I would really like a full synthetic oil. The VR1 full synthetic is hard to come by. Also, it comes in a 20w50 and 10w30. I don't want to play the mixing game and go about getting two different weight oils, too much work for me.

Work? Mix or straight oil change …you just pour 4 quarts of oil in the crankcase. How it that any extra work. Is the mental part of it all above you?

 

[MurkyAsparagus]

I’m curious what the oat manufacturer calls for oil viscosity

My manual from 1990 states SAE30. for engine and Dexron II for transmission. I've seen places say Indmar came out and said a 15w40 multi viscosity may be run.

 

[alarmguy]

Ours recommended 20W-40, but that was 1995, when oils were far lower quality. Newer engines do indeed recommend xW-30 grades, especially the GM LSx-based options.

Yes, I did a little bit of light research myself and I was surprised to see 30 grades as the specification. To the best of my knowledge, all newer engines now have catalytic converters, so for a newer engine one might want to make sure the oil they use is the recommended one.

I still for the life of me can’t figure out, keeping in mind. This is going back a couple decades. My brothers 270 Sundancer with twin V6s. One year for the first time he didn’t use 25/40 to save money and bought Castrol 20/50. Coming home from a fishing trip not too far off offshore through the back bays of the great South Bay he pulled up to his dock and I remember him calling me and said his valves were clattering like crazy. He directly blamed the oil change with the 20/50 and changed it back to 25/40 with no further issue.
Keep in mind he’s an avid boater in the sense his house was on the water and almost every evening they would be out, cruising and on his days off fishing. He would also do all the light work which included changing exhaust manifolds, but that would be the extent of it and oil, changes, tuneup, etc..

Sometimes it’s hard to figure out what someone did when they blame something but I know my brother well and was never even a thought to question what he was telling me.

I guess this is just one of those “go figure” things but I have to admit I always based my future oil choices with that in mind. So for decades, I stuck to Mercs quicksilver 25/40

This is the first boat now that I’m going off script to 15/50. Which is above the recommended weight, but I justify that with it’s all warm water boating now that we’re in the south and I just assume since I’m not running a straight 25/40 it’s fine. My brother’s experience is when we still all lived up in New York which is a slightly cooler boating environment.

Reading your post again I think that’s a good point that you make. The new oil formulations are far superior to that of decades ago.

 

[Japanese]

I rewatched this video today and learnd that diesel oils high in ZDDP are not always the better choice foe gasoline engines because alond with the ZDDP they also contain higher amount of calcium which to some degree cancels the benefits of the ZDDP.

My manual from 1990 states SAE30.

You can always try Valvoline VR1 10W-30 and VR1 SAE30. They have significant amount of zinc and phosphorus.

I may possible go the ESP 5w40 route like he did.

However, if you want to stay synthetic - yes, the Euro car formula of Mobil 1 will serve you more than well 0W-40, 5W-40 and even 5W-30. 0W-40 is widely available at Walmart, you can use it with a piece of mind. Тhe two 40 grade oils have MB, BMW, Porsche and VW approvals. The 0W-40 is Dexos R rated.

I don't think you need Mobil 1 15W-50 or Euro formula 5W-50.
ESP (emission system protection) is a different Mobil 1 oil (for modern engines) that you don't need and also it doesn't come in 0W-40 or 5W-40 grade.
Remember also, that you can order any oil on eBay and most of them have free shipping.

 

[LouC]

I've done used oil analysis on both the conventional Mercruiser 25/40 and the syn blend 25/50, the latter definitely has more zinc. Both hold up well as far as staying in grade. 1300 ppm vs about 950 or so. The Merc oils are expensive but for a once a year oil change, I think it's worth it.
My old '88 Chevrolet 4.3 V6 has a roller cam, so the zinc isn't critical per se, but a broken in flat tappet engine shouldn't be that dependent on zinc either. I have used Valvoline MaxLife 10w30 in my '98 Jeep 4.0 and it just turned 183,000 miles and the cam and lifters are as quiet as when it was new. The Valvoline MaxLife doesn't have unusually high levels of zinc, last one I checked was like 850-900 ppm.

 

[Japanese]

Here LSJ compares Mobil 1 15W-50 and the new formula of Valvoline VR1 20W-50 and their ZDDP content and their oil analysis as well:

 

[SOUNDMAN5000]

If it was me and my boat I think I would use a Penn Grade mineral based flat tappet designed oil from DRIVEN or Penn Grade 1 ( Green oil) or as a 3rd choice found local at Walmart Valvoline mineral VR1.

I would be sure to change fluids every fall before winter storage, Use ethanol free gas mixed with Sta-bil and Marvel Mystery Oil and ENJOY MY NEW BOAT!