95 dodge ram 5.9L 240,000 miles. uses quart oil every 650 miles. no exterior leaks. here are the compression test results:


cylinder# dry wet
8 140 160
6 140 165
4 135 152
2 115 150
7 140 120 (did the wet test twice to confirm) weird result
5 150 180
3 135 150
1 115 155


looks like I have a ring/cylinder wear problem. what do you guys think?
7 spark plugs were a dry grey color on the base
#8 plug was wet from oil (plug is nearest pcv hose to intake location)
truck runs smooth, cranks good, no noticeable loss of power

 

Check out the plenum thread in the stickies. You probably have a bad plenum and working on a clogged cat.

 

+1 Do the plenum fix then monitor your oil consumption. Did you remove all spark plugs for the compression test or leave them in? I would test again in the near future just to confirm. Sometimes you get a bad reading depending on how the test is performed. (like the battery getting drained and engine not cranking as fast) If you get same results it gives you a good picture of how she's doing and how much wear. But since it's running good I'd not worry too much, just something to monitor over time.

A cylinder leak down test will give you a better picture of ring and valve wear.

 

I did the test with the plugs out.
I replaced the plenum gasket about 24,000 miles ago. the gasket was blown but did not notice much improvement in oil consumption after the replacement (about 1300 miles per quart of oil at that time).
HOWEVER, I did the "poor man" version of the repair: I used the original plenum plate and bolts, so I suppose the gasket could have quickly failed. I will probablely soon remove the throttle body and check inside the intake manifold for oil pooling.
thks for the comments.
Has anyone successively used oil additives to reduce oil consumption?

 

Try replacing the PCV valve. Go to the dealer to get it too.

 

If you are still losing oil after plenum fix then do leak down test.
Some oil in intake is normal, so question is how much oil indicates a bad plenum gasket? I guess look for oil coming in from any particular direction and that would be an indicator.

I've used Marvel Mystery oil in big diesel trucks, sometimes with lots of luck it can help the rings seal up and also helps smoking trucks not put out plumes of white smoke. Add a quart to your crank case. Worth a try

 

1. I had replaced the pcv valve recently with an aftermarket one (from advance)
2. the only oily spark plug was #8 (near the pvc intake to manifold), so maybe too much oil is getting thru the pvc valve
3. I plan now to replace it with a dodge pcv valve. I will let everyone know if it makes a difference

 

just replaced puralator pcv valve with a dodge mopar pcv valve. will post a new thread later when I have driven enough to evaluate the valve,s performance.

 

Hopefully it helps. Mopar is the only PCV to use in my experience. My truck has also always used oil - 2 quarts per 3k miles. It used to use more until I switched to thicker oil. Not many people think of this anymore, but talk to any older gear head and they say to run thicker oil on older engines. I've used 10w40 or 15w40 since about 80k miles. If I run 10w30 or synthetic, my oil usage goes way up. It's been steady all these years at one quart during oil life and second tells me time to change. I had Hughes plenum installed way before 100k and didn't change a thing. Also just fixed all leaks underneath (rear main, front main, oil pan) and same results.

So with the new PCV, also try Maxlife 10w40 and see how that goes. . .

 

I have switched the puralator pcv valve with a mopar and I have not experienced an improvement. I will probably now examine the intake manifold interior and if I see any liquid oil I plan to take it back apart and redo the plenum gasket repair.