I'm going to change the PVC hose today assuming I can buy one, and also change the oil and switch to Castrol 5w30. But like you say, there is surely something wrong here - how is that much oil disappearing without a trace? And the truck still running great except for this pesky misfire, which I'm starting to think may be a loose connector. There was a thread talking about if a clamp broke off during the change process (one of mine did) then it won't make a good connection.
I have run about 4K now on my Royal Purple switch and seems the oil is still being consumed about the same rate as before with the MC oil.
It also seems to be about the same color as the MC oil at about the 3K mark, so I think the detergents are near the same based on that seat of the pants check.
I am going to do another oil change this weekend and use the RP one more time. If I don't notice any difference or slower use of oil, then I will switch back to MC 5w20 since it seemed to be working just fine at a substantially lesser price!
Seems this oil consumption is a great mystery and my bets are that the valve guides are seeping oil by since if you start the engine cold, run for just a minute to move the truck and then next time start it later when it is cold again, a burst of smoke comes out for a few seconds. That does not happen if you run the engine to warmup after a cold start and then turn it off. Only happens when you do a cold start and cold shutdown and it sits for a bit.
My truck used to do the puff of smoke thing in the scenario you described and my dad said his truck did it too. Both didn't do it after we changed out the factory exhausts and cat on our trucks. I think the puff has something to do with the stock restrictive exhaust and extra fuel being pumped into the motor. I got a good whiff of the puff cloud smoke and it shure didn't smell like oil. Now if I move my truck and shut it off in short order it will run rough for a very short period of time but no puff.
Is it possible to cause this oil consumption problem by running a thicker oil like SAE 30 or 10w40 for a a few hundred miles, towing a load, and then switching to 5w30, then 5w20? Could the higher viscosity oil change something in the engine that then makes the thinner oil vaporize thru the PCV system or seep thru the valves more?
I think Krewat has eluded to evaporation in the past on semi-syn. I have a jug of Castrol GTX 5W-20 ready to go in on the next oil change to see if my consumption stops or slows.
Finally have almost 1500 miles on the Castrol GTX 5W-20. When I first change oil, the oil is about half way between min and max. After 1500 miles on MC 5W-20 I would be at the min mark,assuming this would mean I burned a half quart in those 1500 miles. With the GTX, I'm what would be a quarter of the way up between the marks assuming this would mean I burned a quarter quart in the 1500 miles. Might be something to Krewat's thinking on semi and full synthetic oils evaporating at a higher rate than conventional oil.
Have been meaning to post back on this also....When I switched over to the RP 5W20, the first 1500 miles seems pretty much the same as Antelope...down to just above the low mark. I went 4500 miles and then decided to change the oil. I did add a quart during that period.
The second change, upon 3K miles, it was only down 1/2 quart, so less consumption than before. Seems now to have gotten better. I have not been able to keep track of usage lately and will go about 5K or so miles then make the change and then track it again. It is possible that some cleaning has taken place here with the full synthetic, but not sure on the cause of this. Just seems to have improved with the RP 5W20 so far for me. For sure, will stay on course for a bit. Possibly, could move to 5W30 also and see what happens.
My 2000 F350 V10 burns around a quart to 2 quarts in 5000 miles. i run Napa Gold oil filters(WIX) and Napa full synthetic oil 5w20 or 5w30(made by Ashland aka Valvoline). My truck has 74,000 miles on it. i recently tried adding a half quart of the Lucas oil stabilizer. Not sure if that'll help with the oil consumption, but its good stuff to use. it seems to me that the modulars just seem to burn oil when u get between 2500 and 3500 rpms, especially when towing. My V10 does it, and so does my buddies 4.6L with 190,000 on the clock. So they basically burn oil where they make theyre power.
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