Burning Oil A Lot Of Oil But Not Smoking All The Time

Martman

Active Member
Jun 20, 2016
163
23
28
Louisville, KY
I am going through a lot of oil. I noticed the smoke much more once I had a full OR exhaust put on.

I have to find time to get the compression test tool and do the test. Pretty much all related oil controlling gaskets have been replaced. (lower intake, rear main, valve covers, pcv grommet, pcv screen)

It is probably a combination of rings and valve seals but based on the following info I think the bulk is with valve seals.
  • It will smoke when I hit the gas after I decelerate. The amount of smoke is based on at what rpm I downshifted or let off the accelerator. This is the norm of valve seals when the vacuum is high based on what I have read.
  • It does not smoke when sitting idle or cold start. This is NOT THE NORM of valve seals that I am aware of.
  • It will smoke a little when I hit the 5K + rpm range which to be honest I don't do very often and on a stock motor with 77K miles that has not been maintained by PO that is kinda expected.
I drive it daily right now and if I do a lot of city driving where I have to decelerate a lot it will drink oil damn near at the rate of gas.

I have never had a vehicle with bad valve seals so my expectations and diagnosis is cloudy when I noticed it doesn't smoke at idle or cold start. The vehicles with bad rings that I have had smoked the entire time.
 
  • Sponsors (?)


Yes all is stock and working as far as I can tell. It has new grommet, pcv, screen, vacuum lines, intake gaskets, etc.. I originally thought it was the lower intake gasket since it was leaking pretty bad out the back but has not improved.

The only time I see the smoke is if I am decelerating with engine braking and then hit the gas. I am sure there is some blow-by in upper rpms but not noticeable in normal driving. That's not to say it isn't burning oil in normal driving and just not smoking enough for me to see it as I drive.

I am going to do a compression test soon. Just have not had time. I appreciate the ideas though and I am going to triple check PCV and stuff because the build up and such that was in EGR and intake tract was pretty rough when I got it.
 
Okay so I finally got around to doing the compression test and really really surprised at the results. The results are below with the biggest difference from highest to lowest being 8%. So with those numbers I did a driving test and really paid attention to when I could see it smoking.

Hard acceleration running through the gears with pretty quick shifting and I don't really see any smoke until I get close to 5K rpm and it might have just a touch.
However, I did two passes where I went through 1st and 2nd and then just let off the gas in 2nd and let it engine brake down to about 1700 RPM. When I hit the gas after reaching 1700, OMG, did it ever billow the blue smoke. So then instead of doing a higher rpm engine brake I did a normal routine drive up to 3rd gear to about 2K and then just let off the gas as if I was in traffic or something until I got down to about 1400 and then just hit the gas as to gradually speed up and again seen the smoke (obviously not as bad) but definitely visible from in the car.

Based on what I have read this points to valve seals does that seem right? And if so what valve seals does everyone suggest?


1 - 141
2 - 150
3 - 140
4 - 145
5 - 151
6 - 142
7 - 150
8 - 140
 
It had a new pcv valve and yesterday I replaced it again just to make sure but still getting smoke when I engine brake and then hit the gas to pick back up. Maybe it takes a bit for it to clear out. Outside of the PCV valve would it be accurate to think the valve seals are the next piece of the puzzle?

I had someone tell me it could be the oil control rings sticking but I would think that would be visible under acceleration and deceleration scenarios.

Also does anyone have a part number or anything from like Summit or Jegs for the appropriate valve seals?
 
What temp thermostat are you running? Factory calls for 192 degree. If you are running cooler it may cause extra oil consumption. Proper oil control is designed to be achieved when the ring clearances are formed by the factory specified operating temperature.
 
So getting back around to the stang for a bit. Below are the plugs from the 7 & 8 cylinders. These are the only plugs that ever look as though they have any oil issues that I recall so I figured I would start with them.

What I have done:
New PCV
Replaced Lower intake gaskets
Valve Seals
Compression tests all good

Can you tell if this looks like oil control ring/piston oil build up or valves?

IMG_0567.jpg IMG_0568.jpg IMG_0569.jpg IMG_0571.jpg IMG_0573.jpg