I have a 2000 F-150 xlt off road with a 5.4. I have owned the truck since 2001. The truck has 170K miles on it and I change the oil between 3-4K miles. The last couple oil changes I have I have noticed I haven't been draining as much out as I usually do, this past oil change was about 3 quarts low. I thought it was very odd. the truck runs great and does not smoke or leak oil. This morning I got in and noticed a tick or slight knock, thought maybe it needed warmed up. After a min. I shut it off and checked the oil, to my surprise there was next to no in the engine! This has me very worried now. I haven't checked my coolant since last oil change so I'm not sure if that's where it's going. Anyone have ANY ideas and where to start looking, I'm missing like 5 quarts of oil in 3300 miles. Again the truck run great and does not smoke at all. I was getting ready to change it this weekend, always run Pennzoil high millage 5w-30.

 

If you don't see any smoke from the exhaust, it's not 'burning' at the intensity you say in the thread title.
If being burned in the cats at that rate, the cats won't last much longer.
Checking oil level;
1. The level is still ok even if at the lowest line. The cross hatch area is a buffer zone for long term as long as it is being checked over the time interval.
2. Checking after running is not the best indication of level because there is to much up in the heads' area than may have not fully drained back to the pan.
3. Look over the engine both top and bottom for any wetness.
This will spread the oil over a wide area and draw down the total level over time without being seen to easy.
4. It's possible the intake valve seals are hard and worn letting oil by and into the intake under high vacuum when decellerating.
Normally you would only see the signs of this upon accellerstion when the cylinders are being cleared.
5. A combination of all these on an aged motor.
Good luck.

 

change out the PCV valve and retest.

 

Do you check your oil weekly? If your engine is using oil you should check it more often .Check your PVC valve .You could have a sludge problem sludge in the heads not letting oil return to oil pan .also if your burning oil at the rate of 1 qt per 1000 miles you wouldn't see it .Have someone follow you see if they see blue smoke when your accellerating..You could have sludge up piston rings .Pennzoil is famous for sludge problems.At least it was 20yrs ago.

 

compression test

 

mine is high miles also, i like to run 10w 30 synthetic in mine, its a tad heavier, but like what everyone else said check for leaks and smoke, hopefully you dont need to put a set of rings in it.

 

i can relate somewhat, my dads 4.6 178,000 miles burns roughly 3/4 to a quart every 1,000 miles but never smokes out the tailpipe or leaks oil, is there somewhere else that it burns that wouldn't show out the tailpipe?

 

yup, right at your exhaust leak

 

2001 v6 180k miles, use Valvoline full synthetic 5w-20.
It used 1 quart every 5k miles until i changed rear main seal. Most oil was driping out going down road, barely saw it on drive. After that it used 1/2 quart every 5k miles until i replaced PCV. Now every 5k miles, when i change oil/filter, it uses less then 1/4 quart. Which some of that loss is still leaking out the valve cover gaskets.