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Mobil 1 question

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Hopefully this doesn't become a "hot topic".....anyway, since purchasing my boat, I have continued to run Mobil1 15-50....as that was what the original owner was using. As I'm soon to be doing the season end oil change, I've noticed that it has become very hard to find.

I will continue to use a synthetic (preferably M1), but the question is....what available viscosity is best suited to transition to for my monsoon... here in the northeast?


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I have good luck with 5W-30 M1, works well. For a boat you really don't need the lower (first number) end viscosity since we don't start them in cold weather. The SBC engine is validated for a 30 wt oil. I do think that most weights are actually offered at Sam's or Costco, you might check there.

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M-1 also comes in 0-40 and 10-40 viscosity. The 15-50 is still readily available, check the diesel truck section of the oil displays. If you have the monsoon or carbed engine, I don't see why you are running 50 weight oil.

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sorry, still a bit confused....here is some more info....

-confession...I don't really understand what the viscosity numbers mean

-I checked three Wally Worlds (where I always used to get the 15-50)...yes, checked the diesel section....seems like the available (diesel) offering in M1 now is 5-40 or 0-40.

-usage temperature range (in my parts) are highs in 90s F in peak summer to lows of 45 F in Spring & Fall.

Sticking w/ a full synthetic, am I okay going w/ the M1 5-40?

would 0-40 be any better?

I don't recall seeing a Synthetic 15-40 (but possibly was a Rotella T6)


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Dave, viscosity means resistance to flow, the higher the number the more resistant. Oil has to flow to lubricate and flow uniformly. The higher the viscosity number, the more uniform the flow but it is slower. So being that you want uniform flow and good flow, the engine manufacturers had to find a good midpoint and, for our engines, picked 40 weight oil. 50 weight flows more uniform but slower, and 30 weight flows faster but less uniform. Hope this helps.

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I found it only in qts at auto part stores ... in that weight. The cheapest I found it was a 6 pack in qts from Amazon, just got mine 2 weeks ago. I search and search for it in Gallons.

FYI and will believe it when I see it:


Edited by MalibuNation
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I was golfing with the technical rep for a local Exxon/Esso oil distributor who has the same boat as me (08 HH etc). He runs Mobil Delvac (which is synthetic) 0W40 in his HH. If you look at the shear stability and and viscosity rating at temperature (100 C); it is better than a straight 40 weight Pennzoil marine as speced for HHs. If you warm up your boat properly (like you have to with straight 40 weight anyway) you are in a better spot at operating temperature with the 0W40. Side benefit is quicker lubrication at cold start (70 F is still a cold start when all the oil is in the pan) and less wear on starter (minor benefit). If you run 15W40 in monsoons and earlier the 0W40 is an option. You need make up your own mind but I run 0W40 Delvac in my 08 Duramax year-round and have switched over to 0W40 in my HH after reading and comparing the literature. I used to ship 40W Pennzoil marine from the US but that dance can thankfully end.

Edited by G-Mack
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I am planning on running the Shell/Rotella T6 synthetic 5W40 in my boat. It is pretty cheap for a synthetic and readily available at my local Wally World. I am running it in my Cummins and "seems" to be doing it's job in that motor. The 5W40 really lets it start up easier in the winter when temps get cold around here, so I figure why not let the boat motor start up easier. Plus, I only have to buy 1 oil for both the truck and the boat.

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Just a quick FYI........Autozone has Mobil One oil change kits on sale right now for $33. That's 5 quarts of what ever weight and the M1-302 filter. That saved me $24. Almost a 2 for 1 oil change. Not bad. :yahoo:

p.s. I bought 5W40 diesel oil.

Edited by gorilla
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