My 2005 f150 Lariat 5.4 started to use a lot of engine oil since the last two oil changes, no leaks to be seen. Where can I start to diagnose the problem?

 

How many quarts per 5k mi . ! or 2 not unusual.

 

It's been about 2 qt's in the past 2,000 miles.

 

I have heard of pressure in crank case causing this . Maybe thru the pcv circuit which is the valve cover on drivers side . Some add a catch can in that side to keep intake clean. Place dry newspaper under her when parked to spot drips . What does exhaust look like ,white black? There have been cases of chain eating thru valve cover and timing cover.
Valve seals /rings /rear main seal . Haven't heard much trouble with rear seal, it does have a reputation for sticky valves . There is a seal in front of timing cover on crank . Just clean her up good and see if leaking at highest point . I use dawn to clean up oil / cheap and doesn't harm seals . I like a little oil left on metal to slow corrosion especially in salt country . All cover seals have to have a dab of rtv on metal joints on their metal surfaces oil pan/timing cover/valve covers/ keyway in timing cover ..
Don't get water up top in cly spark holes,,this engine does not take cleaning well on top side .
There are tests for rings etc , I'm sure someone will chime in with them if this persists.Of course a compression check .
1 quart per 2000 mi is near normal for some of us .

 

Following. I have the same issue.

 

I took mine in to the shop. they said no leaks, no burning, and they don't know where the oil is going, but want me to keep track of how much oil I put in, in between oil changes.

 

Have you replaced the PCV?

 

son had a 2006 EXPEDITION doing that last summer... I told him it was burning thru the PCV.. We looked and there is not a specific "PCV" part ..... but I still think it was burning it... 3 months later he had the famous timing chain VCT problems that got out of hand and motor needed a rebuild........... Did the low oil level / psi cause the VCT problem, or did the worn VCT / chain parts do something internal to cause the oil burning ?? ....... I don't know, but don't let the oil level to get low and drop the PSI.. not good for the VCT / chain adjusters.

 

PCV is in valve cover drivers side . I cleaned mine during timing job even tho you are not supposed to but who is going to buy a whole new valve cover for that .I wonder if the crank case is getting pressurized in these high usage ones .A temporary catch can could tell if its going that way . I wonder if you could rig small engine gas filter in that line on drivers side.
If it isn't leaking then it must be burning it . Its not like its a squirrel and burying it. . Sounds like it needs a ring check .
I know mine uses at least 1 quart per 2k but what is the limit you should put up with . Guess this is hard on cats .
Wheres the real mechanics when you need em ? Mines at 195k some on here close to 250k .

 

Looks like over the last 1,000 miles it hasn't used any...?? Tomorrow I'm heading East on a 1,600 mile trip and in three weeks coming back again so that will give me a good indication of oil usage, will keep you posted!

 

my 06 has 95,000 miles it's PVC is built into the valve cover like the fella's above. I leave Saturday for a 1800 mile trip pulling my Jeep on a trailer, I will check oil each gas fill, and keep track of it.

 

So, It's been about 3,000 miles since my previous post, changed the oil in between and still loosing about 1 - 1 1/2 qt every 1,000 miles. Should I do a compression test on all cylinders to see if the engine is getting tired?

 

If your motor was "burning" the oil through worn rings you would certainly know by the look and smell of the exhaust. There's no mistaking it. You really want to look at the PCV system. Pull your intake manifold and I can almost guarantee that you'll find a fair amount of oil in your lower intake manifold. Betting at least a 1/2 pint or more. It's being blown into your cylinders and it's being atomized with your fuel. When you pull the intake you'll see a lot of gumming and sludge in your intake runners on the cylinder head. THERE is where your oil is going. The PCV system is so easily over looked because so many folks don't really understand what it does and how it works (I'm not saying that's the case with you).

The catch can idea redfishtd is suggesting is an excellent idea, but I'd just pull the intake. It's not hard and you will see exactly what I'm talking about. Happened to both my 4.6 and 5.4.

 

So, If I do what you suggest (which will have to wait till I'm back home east again in December), should I clean the PCV valve?

 

Just so everyone is clear, the PCV is in the intake and not in the valve cover. The valve part is Ford part# is 9F624 and shown here in the picture, its held in with two bolts and a wiring connector as its heated.