I just thought it was odd. What percentage of oil is a 25w and I really don't see the point considering boat engines tend to have excessive cooling. On top of that it's a synthetic blend for a 4 stroke. Who is the one person that runs this? I can't imagine the production costs for something so benign
Odd duck of an oil
- Thread starter FlyingTexan
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4wd
$50 site donor 2026
It could pretty much be a mono that won’t shear …
That was Merc’s goal per their tribologists …
It would be interesting to know the amount of VM.
4wd
$50 site donor 2026
Tuna Pro is low zinc so the cats like it
4wd
$50 site donor 2026
I'd have no issue using it in a mower or gen. set. Boat motor runs a long time at higher RPM's than OPE at 3600.
Only issue would be cold weather starting with the heavier oil.
Only issue would be cold weather starting with the heavier oil.
I run 25w40 in my Mercruiser 4.3, that's the standard for stern drive engines.
With a pour point of -36C it shouldn’t be a problem….unless you’re ice fishing
There´s A LOT more there than just bass fishing stuff. I´d never be able to escape with just oil. But for the savings, I might come out with what ammounts to free ammo, a couple lures, or something else that catches my fancy.
A good example of how a low pour point doesn’t automatically result in a superior winter rating.With a pour point of -36C it shouldn’t be a problem….unless you’re ice fishing
It's not an Odd Duck of an Oil.
Quite common, Mercury Marine has had this 25w-40 oil for at least the past 40 years.
Pretty much it's a straight weight 40 with a 25 pump-ability rating. Im sure over time there has been some changes to the formulation but not to the 25w-40 rating.
Japanese
$50 site donor 2026
So, you had nine 4-stroke boat engines and neither of them was spec'd for 25W-40 oil? Have you read their owner's manual? What were those engines and what oils have you usually run in them?
Seems like it was probably 15w-40. I’ve never personally seen a 25W40 either… because if an engine is that lax on its cold requirements… it probably just says, “throw any 40 grade you have in it”
4wd
$50 site donor 2026
Lots of the outboards call for FC-W in 10W-30 or 5W-30Seems like it was probably 15w-40. I’ve never personally seen a 25W40 either… because if an engine is that lax on its cold requirements… it probably just says, “throw any 40 grade you have in it”
The stern drives are where these thicker lubes wind up …
Ha the good pcmo oil is around $25, the better oil at that store is usually around $30.
Diesel engine oil can be had for even cheaper.
It usually always ends up on the clearance shelf in the fall.
I don't have hard data on this but given Mercury and Mecruiser's recommendations over the years, they may have found that sterndrive engines (old school inboard designs) shear down oil faster than modern outboards do. That may be why they recommend 10w30 for outboard but for inboards, it's always been 25/40. They also sell a high performance syn blend 25/50 for the Verado outboard but that is a special case (supercharged engine). Their consistent recommendation for many years has been either the mineral 25/40 or syn blend 25/40. So the Pennzoil in question is just matching up with Merc's long time advice. And it is cheaper!
Most likely because you have outboard engines.
25W 40 oil was the main state of MerCruiser in board and I/0 engines for decades. This also includes the commercial category.
Going out on a limb, it might’ve been the same for at the time OMC and some Volvo engines
You’re not understanding what a 25W rating is.
25w is not the weight of an oil. It is the winter rating of how an oil will flow in cold weather. (pumpability)
I can speak for Mercruiser Quicksilver 25W/40 oil
It is a straight weight 40 oil. It does not use viscosity improvers that can break down.
The cold rating pumpability is 25
That might actually be for many straight 40 oils but Mercury is specifically engineered to that specification 25w/40.
What part of my statement said otherwise?
