4-stroke oil ?

scott craven

Well-Known Member
What 4 stroke oil do you guys run in your outboards ?
I have been using Castrol or Penzoil 10w-30.
it's not marine specific however, and wonder if that could be a problem ?
 
10-30 Castrol Syntec auto oil for many years in my Yam 150's.
Don't let those dealers tell you that their marine oil is magic.
My buddy is a chemist for BP.
 
once the warranty is up i will be going full synthetic.
 
I usually buy yamalube by the case. Most dealers will give you a decent discount if you do. Tightens up the price difference if you do this.
 
Just passing on what my Yamaha mechanic told me - He said the Yamalube is a synthetic blend. He said a pure synthetic put in the Yamaha which is not run all winter like mine would harm the seals. If run often no problem.
 
What ever the oil you use, castrol, quaker state, pennzoil etc. Just make sure it has the specs your engine requires. nuff said
 
They did a comparison of marine oils vs automotive oils. I believe the marine oils had much higher detergent and rust inhibitor levels. Otherwise the same.

Sorry I don't have a link but you should be able to find it with the google machine.
 
I do mine every 100 hours.
My Yamahas make oil so I should probably do it every 50.
I start with the oil level half way up the stick and it goes up about 1/2" in 100 hours.
 
I do mine every 100 hours.
My Yamahas make oil so I should probably do it every 50.
I start with the oil level half way up the stick and it goes up about 1/2" in 100 hours.

That would indicate your motor's are running too cold, incomplete fuel burn leads to fuel in crankcase.
check thermostats, they may be stuck open ?
 
That would indicate your motor's are running too cold, incomplete fuel burn leads to fuel in crankcase.
check thermostats, they may be stuck open ?

Thermostats are fine.very common with Yamaha 150's.
Most techs will concur.
All outboards run too cold up here.
 
My yamaha was making oil and the mechanic said it was normal. I ordered and changed the thermostat and the issue went away. It turned out the old thermostat wasn't stuck open, it just opened at too low a temperature.
 
ok 100 hrs ,well I put on about 50hrs a year in good year, try to change in fall.Have been using yamalube , maybe give the Castrol a go, save a few bucks.thanks for the info.
 
I would research that, fuel will contaminate the crankcase oil
breaking down the lubrication quality of the oil.

Done lots of research on the subject.
The advice came straight from one of the techs at SIM Yamaha.
Lots of 4-strokes make oil for the same reason (9.9 Yam and Merc).
Outboards are designed around a much higher average water temp.
 
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