By lots of oil I mean 2 quarts in 200 miles. Has 60k miles on rebuilt motor, done professionally. No leaks I can see, nothing on the ground or motor. Does every so often let out a puff of black smoke. Does not smoke otherwise. I haven't seen it, just what I've been told by people following, said it happened 3 or 4 times on a 10 mile trip. Sometimes would have a miss, some times ran fine. Was usually gutless, but sometimes was fine. Would have it scanned at orielys. Sometimes read a miss, sometimes not, even though you could deffenently tell it was not running right. Also has an occasional "hiccup" where it will backfire and stutter for 5-10 seconds then goes back to normal like it didn't happen. Thinking maybe a plug or coil was going bad giving low voltage, I replaced plugs and coils, runs much better, the miss is gone but still doesn't always have the power its supposed to. Has had the "hiccup" once since then. Still uses the same amount of oil. Tried switching to 10-40 oil, no change. Has dual exhuast no cats. Installed a backup camera yesterday and noticed noticed oil coming out the left tailpipe. All the plugs had looked fine when removed. I've been told pcv valve but also heard those shouldn't need to be replaced on these models, its built into the valve cover. Nor would I think it's rings. Will be having it programmed to have the O2 sensors deleted and to shift into overdrive later instead of at 900 rpms... Do you think that will help? Can't figure out what the problem is. Would bad valves cuase this? Took it on a 100 mile trip the other day, checked the oil the next morning before I leave and it was fine. A few days later after only going 5 miles to town and back a few times it lost 2 quarts. I always check before I leave when the motor is cold. About 80-90 degrees outside

 

if its burning oil, its going thru the PCV valve, around the rings, or down the valve guides. The PCV valve is a simple test......... I don't know about "built into the valve cover", but I would replace the valve or remove and let the valve cover vent to atmosphere for a test.

 

The PCV on the 5.4 3 valve is a metered orifice built into the valve cover. If it gets clogged oil consumption will go up. If the ring gaps were excessive or lined up during the rebuild the engine may use obscene amounts of oil but it would probably run like crap as well. Just a few things to consider.