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Discussion Starter #1
I noticed recently that the 351M in my wagon has started losing quite a bit of oil. Since there's no evidence of a leak, it seems most likely it's burning it. I think it's likely since often quite a bit after startup, when it's running really rough after starting there's often a cloud coming from the exhaust. On these motors, is there a most likely culprit to be the cause? If so, is there an easy fix or way to at least partially mitigate it? Or am I just going to have to deal with it until I can get the motor/heads rebuilt/replaced?
 

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You could switch to a thicker weight oil but imo its a bandaid. Ive heard people talk about Lucas and Seafoam but I dont buy into it.

Do you have a vacuum gauge or compression tester. I recommend hooking up the vacuum tester and take readings at idle, quickly snapping the throttle open and holding the rpms at 2k rpms for 30 seconds. If all checks out then go to the compression test.
 

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You could switch to a thicker weight oil but imo its a bandaid. Ive heard people talk about Lucas and Seafoam but I dont buy into it.

Do you have a vacuum gauge or compression tester. I recommend hooking up the vacuum tester and take readings at idle, quickly snapping the throttle open and holding the rpms at 2k rpms for 30 seconds. If all checks out then go to the compression test.
Well, I'm using 15W40 most of the time, since I can get it with zinc already in it without spending top dollar ($20 for a bottle of zinc for one oil change). Now that you mention doing a vacuum test, it makes me think I'll need to do that. I'm now a bit suspect there's a leak. Don't think I've ever done a compression test on it, but I have the tools for it, so I'll check that. Poor compression could indicate too much oil getting around the rings, right?
 

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Check engine PCV valve is o.k . Could be valve stem oil seals . Carry out a wet / dry compression test .
Well, I replaced the PCV valve in 2016 shortly after buying the car. But I can imagine it couldn't hurt to see if it's soaked in oil. Valve stem seals were something I was suspecting, but have no idea how to check for.

Also, what's the difference between wet and dry compression tests?
 

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The thing is oil can only get into the combustion chamber from pcv, worn rings and worn valve seals. A compression test will reveal this.

Im a big proponent of vacuum testing because its non invasive, simple and very informative. Not only can it show mechanical issues but it can show things like clogged exhaust and timing being off. I would still do a wet and dry compression test afterwards to verify rings and seals are good or not like Logan suggested.
 
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