15w50

[SkiDad]

Hi There, certainly don't want to start a which oil is best thread - i know they are all good these days

My question is simple - is 15w50 Mobil 1 a lot thicker than most 15w40 ? It's what the PO put in and seems to run fine. I'm not worried about the cost of oil. I'm questioning if it's too thick and should go back to 15w40. I boat from 50-95 degrees.

 

[Scott Danforth]

15w50 is a bit thicker than 15w40. however since many motor companies recommens 20W50 I have no problem saying use either the 15W40 or 15W50 or 20W50

 

[MH Hawker]

the oil for a motor is rated for the motor tolerances

 

[Chris1956]

Gee, I would recommend you use what is recommended by the manufacturer. Some years ago a new standard for oils used by :Four Cycle Water Cooled (FC-W) motors was created. OEMs usually specify an oil that meets this certification. I would recommend you use that versus what the PO put in.

Automotive motor oils are not always the right choice for a marine engine.

 

[Scott06]

I'd use what ever weight gives you 10 psi per 1000 rpm what hot and under load. As an engine wears you may gave to go thicker to keep the psi up.

 

[SkiDad]

thanks guys for the advice. The engine is a V8 direct drive with 405 hours. The owners manual says 15w40. I don't think Mobil 1 comes in that weight, so I think that is why they went with the 15/50. I do know they ran conventional oil the 1st 100 hours and then switch to synthetic after that.

Anyhow, i know i have good PSI but i have to monitor it better to see what the numbers look like, just had a the boat out a few times so far this year. Seems to get oil pressure in 5 seconds after starting. Is there such a thing as too much oil pressure ?

it's all new to me, i had 2 stroke outboards all my life and no oil to change - ha ha

 

[Mischief Managed]

Assuming the oil meets other requirements and regarding viscosity only, you cannot go wrong with the smaller number being smaller or equal to the recommended rating or the larger number being larger or equal to the recommended rating. Thus, 15W50 and 5W40 are great replacements for 15W40, but 20W50 and 5W30 would not be good replacements for 15W40.

 

[BRICH1260]

I think you will be fine with the 15-50 synthetic.

 

[Mischief Managed]

. Is there such a thing as too much oil pressure ?

Indeed, too much oil pressure is bad. There is a pressure relief valve that will prevent over-pressurization; if it sticks, the oil pressure can build enough to blow out the oil filter seal. Had that happen on a car once.

 

[SkiDad]

I've been watching my oil pressure the last few times out - with the M1 15w50 this is what I have

Idle Cold: 45
Idle Warm: 35
Ski/Cruise: 50
WOT: 60

good, bad ?

 

[R055]

I've been watching my oil pressure the last few times out - with the M1 15w50 this is what I have

Idle Cold: 45
Idle Warm: 35
Ski/Cruise: 50
WOT: 60

good, bad ?

Looks good, only psi readings I'd be concerned with is less than 10psi.

 

[ondarvr]

Don't stress over it, people all kinds of oils and different weights in their motors, put the correct product in next time and go on with life, one session of a slightly higher visc oil isn't going to create a problem.

 

[rallyart]

I use Mobil 1 5W-40 in my boat. The upper number is what you are at while operating for any length of time. The W number is the viscosity at startup. A 5W oil will get the engine lubed faster than a 15W and not create any operating issues in a boat. The 50 weight just means you are working harder to pump the oil. There is no problem running 15W-50 but your power is down a bit as a result.

You need to have 35 psi, or above, in a small block chevy at 5000RPM. 60 is a bit high but it won't damage the pump shaft.
So, to answer the question it is not bad, but not ideal. I have run many dyno tests on race engines checking various oils. Mobil 1 is my favourite but most major company pure synthetics are good. Conventional oils are fine too, in a boat, but I use synthetics exclusively.

 

[SkiDad]

I've actually been thinking of switching to Mobil 1 5W-40 - glad to hear someone else is running is successfully. My engine at WOT is 5500 - my operating range is 5200-5600 at WOT (it's an Chevy 350 LS1 engine)

 

[bruceb58]

I wouldn't use 5W-140. As noted in the following Volvo recommendation, they don't even recommend 10W-40. Last couple lines in the last paragraph on the right.

 

[rallyart]

It is interesting that Volvo makes several of those recommendations. Almost every study in the last 40 years has indicated that multigrade oils are at least as good as single viscosity and I've never seen one that rates conventional over synthetic. In a boat running only in summer conditions would be the just about the optimum for Volvo's recommendations as the engines should run cool and the ambient temperature should be high.
Following those ideas is not what I would do, even if I had a new Volvo. But that is my personal opinion.

 

[oldjeep]

Indmar says 15w40, so that is what I would use. If you want synthetic, you can get that weight in rotella , Delo or royal purple - just make sure it is sn or Sm rated.

 

[bruceb58]

It is interesting that Volvo makes several of those recommendations. Almost every study in the last 40 years has indicated that multigrade oils are at least as good as single viscosity and I've never seen one that rates conventional over synthetic. In a boat running only in summer conditions would be the just about the optimum for Volvo's recommendations as the engines should run cool and the ambient temperature should be high.
Following those ideas is not what I would do, even if I had a new Volvo. But that is my personal opinion.

In any case, I wouldn't use 5W-50. No reason unless you boat in a very cold climate.

 

[H20Rat]

Mobil 1 is my favourite but most major company pure synthetics are good. Conventional oils are fine too, in a boat, but I use synthetics exclusively.

You have better luck with M1 than I did... I religiously send my used oi samples out for testing, and M1 is consistently one of the worst oils I've ever run. It sheers badly, 5w-30 quickly ends up out of grade. Rotella T6 is one of the better ones, M1 extended protection oils aren't usually too bad.

(Disclaimer, this is with engines far more abusive than a typical marine engine, think high revving high horsepower turbocharged 4 cylinders)