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Old 15-09-2019, 18:04   #1
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2gm20F Oil Consumption

My new to me, 32 year old Yanmar 2gm20F is burning what I consider excessive oil. I added 10oz after about 100 hrs of running. I'm using Rotella T4 15w40.

The only indication of burning oil is a little puff of blue white smoke when I increase RPM after idling for a short period.

If I remove the oil fill cap while running at the dock, there is considerable blow by. There are no oil leaks. No oil in the bilge. No sheen on the water.

The engine starts immediately when cold and idles smoothly.

I'm guessing I have a ring problem yet the engine fired up immediately when cold and turns up to 3400 rpm I neutral or in gear.

Should I be planning an overhaul sometime soon or should I continue running the engine and closely monitoring consumption till it gets really bad and i chase all the mosquitoes out of South Florida with the smoke?

Would changing to a single grade oil like 50 weight help or harm? I live I South Florida so cold weather starting is not an issue. Anything below 65 degrees Fahrenheit 0, we stay home!
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Old 15-09-2019, 18:45   #2
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Re: 2gm20F Oil Consumption

I have a 2GM20F. You don't say how many hours this thing has. As for oil consumption, they do burn a little, but in my experience, not that much. HOWEVER, my engine only just has a thousand hours. If yours has been used hard, and has say 5,000 hours or more, that might be acceptable. Somebody with more specific knowledge will chime in soon.

But again, often it's the hours, not the years.
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Old 15-09-2019, 19:03   #3
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Re: 2gm20F Oil Consumption

I have no idea how many hours this engine has. My guess is it's original and gas never been overhauled.
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Old 15-09-2019, 19:09   #4
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Re: 2gm20F Oil Consumption

I would not worry about it.
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Old 15-09-2019, 19:56   #5
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Re: 2gm20F Oil Consumption

10 oz in a hundred hours is not that bad. 10 ounces in 5 hours is bad.

The smoke out the oil fill is of some concern. I would check to make sure the crankcase vent to the intake manifold was not clogged. This is fairly small orifice in the brass Fitting that the hose connects to. Also make sure the metal mesh in the valve cover at the vent is clear.

Other things to check is to make sure the discharge elbow is not mostly clogged. That the engine starts cold easy means there is not much wrong with it.

If the engine gets to be hard starting, that is the first sign you might need Rings replaced. An engine with bad rings does not actually smoke that much. It will use a lot of oil. When it gets to 10 oz in 20-30 hours, then it's time to check the Rings.

But 10 ounces in a hundred hours is not at all bad.

Edit: I prefer to run straight 30 weight oil in the engine. That's Shell Rotella T1, Tractor Supply carries it.
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Old 15-09-2019, 20:06   #6
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Re: 2gm20F Oil Consumption

I'd say that's not bad at all as previous posters have said.
You could use 25w-70CF or something similar if you wanted to slow it down but I don't think you have anything to worry about. Sounds normal for a 32 yr old engine.
For the rest Sailorchick has it covered
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Old 17-09-2019, 05:35   #7
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Re: 2gm20F Oil Consumption

Quote:
Originally Posted by sailorchic34 View Post
10 oz in a hundred hours is not that bad. 10 ounces in 5 hours is bad.

The smoke out the oil fill is of some concern. I would check to make sure the crankcase vent to the intake manifold was not clogged. This is fairly small orifice in the brass Fitting that the hose connects to. Also make sure the metal mesh in the valve cover at the vent is clear.

Other things to check is to make sure the discharge elbow is not mostly clogged. That the engine starts cold easy means there is not much wrong with it.

If the engine gets to be hard starting, that is the first sign you might need Rings replaced. An engine with bad rings does not actually smoke that much. It will use a lot of oil. When it gets to 10 oz in 20-30 hours, then it's time to check the Rings.

But 10 ounces in a hundred hours is not at all bad.

Edit: I prefer to run straight 30 weight oil in the engine. That's Shell Rotella T1, Tractor Supply carries it.
Theres no smoke out of the oil fill...only air..theres alot of pressure under the valve cover. But I think youre correct...it might be a good idea to pull the breather cover of and make sure that its open all the way from the engine, through the tube, into the intake.
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Old 17-09-2019, 05:58   #8
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Re: 2gm20F Oil Consumption

4 or 5 oz of oil in 50 hours? That sounds normal to me.
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