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Old 09-23-2017, 12:53 PM   #21
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Thanks Ski,
That about sums it up IMO.
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Old 09-23-2017, 02:51 PM   #22
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Originally Posted by Ski in NC View Post
I've been through a few Ford Lehmans, can't remember once seeing ball or roller bearings.

Regarding the 90F ambient temp: It really does not matter. What matters is oil temp. On the Lehman marinization, the oil is cooled with a sea water cooler without any thermostatic control. Oil temp I have measured on FL trawlers is around the 160F range, WAY cooler than a typical diesel. Most diesels use coolant for oil cooling and oil runs around 190-220F. And many of these spec SAE 30.

I suspect the SAE 40/90F ambient spec was imported directly from the Ford literature, where these engines were run in ag equipment and road vehicles where there was no sea water oil cooler. Oil temps then probably a good bit higher than in marine and may be closely related to ambient air temp.

If your oil is running at 160F and your engine is healthy, there is no need to go to SAE 40. SAE 30 is more than adequate. And 15W-40 will not harm a FL.

Any modern oil is WAY better than the stuff they had to work with when the engine was built.
I believed Ski's info here is right on the money. A significant reason to use a certain viscosity is due to temps at start up to ensure proper flow. The other side is to make sure viscosity is ok when the oil gets really hot but that is not nearly as much of an issue with water cooled oil coolers. I believe that one cannot go wrong either with 30w or 15-40 in a FL. I would be resistant to going to straight 40.

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Old 09-23-2017, 09:40 PM   #23
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I don't understand the resistance to mono 40W. As long as one's engine cranks smartly at startup.

As to flow oil is probably close to totally uncompressable so the oil pump revolves so many times X amount of oil advances through the system. If the engine is running oil flow is insured and lower viscosity is not an advantage ... in this regard.

During the summer I often include a quart or two of 40W. Actually I don't think there is much difference in the thickness of 30W and 40W. Not as the numbers lead one to believe. 20W would seem to be twice as viscous (thick) as 40W. I don't think it's even near that. A small difference.
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Old 09-23-2017, 10:20 PM   #24
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I don't understand the resistance to mono 40W. As long as one's engine cranks smartly at startup.
Oil can be very sluggish and thick at startup, and it is imperative that the cylinder walls receive adequate oil to cool them. When oil pours like syrup it can not wash the cylinder walls and remove the combustion heat.

That is why they say wear happens more at startup than at any other time for a motor. Oil starvation. I have seen lots of dirt bikes suffer from the piston seizing up because they never let the oil warm before racing.

.............

That said, I have a good friend thats been grinding cams for better than 40 years and to this day he swears that his empirical evidence shows that a straight weight diesel (rotella) will protect the valve train much better than a multi grade.

.............

I run rotella synthetic in everything I can except the genny. It gets rotella 40w, easily obtained from oriellys. Its so much quieter running with it. To me the quieter running agrees with a straight wt oil being better for valve trains. At least for diesels.
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Old 09-24-2017, 06:36 AM   #25
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"There is a downside to heavy weight oils - It takes longer for the oil to flow on startup and in cold weather."

I am not so sure of this as oil in most engines is pumped with a geared pump , the days of a finger bolted to the end of a con rod for splash lubrication are gone..

In coaches and large trucks the thin winter oil is used instead of a block heater so the engine can spin rapidly enough for compression temperatures to get high enough to ignite the fuel.

Thin oil is considered safer than using an alternate fuel, Ether, as it is too common for a driver to attempt to start a warm run out of fuel vehicle with the Ether. This can cost the engine.

"Modern " oil usually just means more detergent , as since '96 many engines are fed their exhaust gasses for the air police , which is hard on the engines.

Single weight oil has less modifiers and additives so there is more oil , in the "oil".
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Old 09-24-2017, 07:36 AM   #26
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Ski's excellent #18 and #20 posts seem on the mark. I might add, use your laser gun to check engine oil operating temperature.
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