20W40 Yamaha Oil Recommendations

[seahorse5]

A while back there was discussion about Yamaha recommending 20W40 grade oil for Southern warm water engines. Here is an excerpt from a Yamaha publication about E-10 fuels and it mentions 20W40 oil use.


...And speaking of oil changes, if you live in the southern region of the country—the hotter states—one of the things that Yamaha has recommended for four stroke outboard owners is going to a 20W/40 four stroke oil in their motor over the 10W/30 oil. The higher viscosity of the 20W/40 allows the engine to run cooler in those hotter regions of the United States.

So if you live in South Texas, Southern California, Baja, Southern Louisiana and Florida, you might want to remember that the 20W/40 oil is going to give you cooler engine temperatures when operating the outboard and also last longer than the 10W/40 oil. Since oil is essential to engine lubrication, you’ll also want to pay attention to the suggested oil change maintenance for your outboard and have it changed on time.




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[robert graham]

Seems like if the cooling system/thermostat is working correctly, the motor will run about the same temperature regardless of geographical area....but if Yamaha says heavier oil is better then go with it!....

[boscoe99]

Seems like if the cooling system/thermostat is working correctly, the motor will run about the same temperature regardless of geographical area....but if Yamaha says heavier oil is better then go with it!....

It does seem strange. As you note, if the thermostat(s) and the cooling system is working correctly then the motor should not be running any hotter in summer time, or at higher latitudes, than it does in the winter.

Now let's take a look at automobiles and pick up trucks. They run much, much hotter than outboard motors do. What does Ford specify for my F150 pick up? 5W-20. It is almost as thin as water.

Some studies report that the majority of engine wear occurs at start up. The quicker that oil can get through out the engine the less wear there may be. A thinner oil is used for just that purpose, amongst others.

Finally, compare an outboard power plant positioned vertically versus horizontally and the way that the oil pan is positioned. It is a much further distance from an outboard motors oil pan pick up tube to the top of the block than it is from an automobile motors oil pan pick up tube to the top of its block. Would seem that the quicker that oil could get flowing throughout the outboard motor (using a thinner oil) then the less wear there may be.

Strange indeed.

[wlewis11]

I've seen that Yamaha publication. Since I live in GA, I have been looking for the 20w 40, but no one seems to even sell it and I couldn't even find it on Yamaha's website.

[boscoe99]

I've seen that Yamaha publication. Since I live in GA, I have been looking for the 20w 40, but no one seems to even sell it and I couldn't even find it on Yamaha's website.

Yamalube

[wlewis11]

Boscoe to the rescue again! Thanks. I see it now.

[wlewis11]

Reading Yamaha owners manual, they actually recommend 10w40 for higher temp ranges (5-105 degrees) whereas the 20w40 (68-105) is the only one available through Yamalube. For those of us in the South, 10w 30 (5-95) might be best all around if 10w40 is unavailable. What do you recommend Boscoe?

[boscoe99]

Given the fact that the operating temperature of the motor is more a function of the thermostat(s) and the water temperature I think either grade of oil will work just fine.

My automobile is not concerned with water nearby lake/ocean temperatures. I fail to see the outboard makers' concern with ambient air temperatures.

If I am fishing below Hoover damn in Arizona, the air temperature may be 105degrees F while the water temperature might be very cold. Which is going to have the greatest effect on the operating temperature of the motor?

[wlewis11]

Good question.