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Hello and thanks in advance for any help. I've searched for this first and didn't find any specific info so here goes. My Case 448 with an Onan B48M is burning 1 quart of oil every tank of gas. We did a valve cleaning job 6 months ago and based on some forums advice have been running 15w-40 Rotella since. Now the mower is doing this. Both cylinders test out at 120. Some posts say we should be running straight 30 oil. I am lost since I am not a mechanic. But I do know one who can do the work needed. Can someone give us an idea where to start?
 

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Rotella 15W-40 is used in the hydraulic system and is added to to hydraulic reservoir. SAE 30 is used in the engine.
 

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One of the most hotly debated topics is oil.

I just consulted two Op Manuals produced by Case for the 446 models. The early one specifies only 30W for temps above freezing. The second one also specifies 30W but shows 20W40 as being acceptable. Of course, 20W40 is a multi-grade oil that has almost disappeared from the scene and 20W50 is the replacement for it.

Both Onan and Kohler state that higher oil consumption is to be expected whenever a multi-grade oil is used. Since your oil consumption is very high, my advice is to switch to 40W to see how much of a difference that grade will make to the consumption issue.

You can have good compression in an engine but if the oil rings on the pistons are not what they should be, then you will burn more oil than what is normal for these old technology engines. Bad valve guides can also cause increased consumption.
 

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One of the most hotly debated topics is oil.


Both Onan and Kohler state that higher oil consumption is to be expected whenever a multi-grade oil is used. Since your oil consumption is very high, my advice is to switch to 40W to see how much of a difference that grade will make to the consumption issue.

I`m onboard with that ^
My ONAN manual ( not Case/Ingy) specs 40w above 80 degrees and 50W above 90. And it bears repeating, the manual specifically states the multi wt oil will INCREASE consumption
 

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Also keep in mind that when you burn oil it will lead to carbon deposits, if you don't know when the heads and piston was last decarboned now would be a good time.
 

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Maybe the breather assembly is dirty and not working properly. Does the air filter have oil on it ? Could be sucking oil through the carburetor and burning it.

:trink39:
 

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Thanks everyone. It was de-carboned this spring. We are going to a heavier oil and will post with an update.
 

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At one point when I had my rental business, I had three Performer 20's on stump grinders, the worse thing you can do with an engine. They are very easy to re-ring. You can probably reuse the original pistons. All you'll need is the rings, a pan gasket, and two head gaskets. A light honing, clean it up well, (don't worry about every little piece of carbon, it will burn out once the engine is running clean), and put it back together. It's much cheaper to do it now than after you run it out of oil, but I've seen that done too with no ill effects. Curious thing about those engines, though, the oil never stayed clean even when they were new.
 

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My 224 was using about that much oil, I've flushed the oil with seafoam, changed it twice now within 15 hrs, with a couple different oils. I just used 50w penzoil gt racing oil I had on hand for my old Harley. I just ran through 3/4 of a tank, and no oil consumption, so thats a plus. I also used a little lucas in the oil.
 

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Update #1. We changed the oil to Valvoline SAE50 (the only 50 in our town) and also discovered oil in he air filter. It seems that someone had removed the steel wool in the past thinking it shouldn't be there. We mowed several hours Saturday afternoon and when we get to the end of the tank of gas, we will measure for consumption and repost. It is running stronger but still has some smoke.
 

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You need to work on the breather system ...... The metal wool transforms the oil mist into droplets that return to the crankcase. Without the wool, the mist goes into the carburetor and gets burned.


:trink40:
 
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