So I changed my oil last night and I only got 4 quarts out of the engine total between drain pan and oil filter. So over the last 5000 miles, I've somehow lost 2 quarts of oil but I dont know how or where. The truck never smokes at all and the underside of the entire truck is completely spotless. No oil stains where it has been running down and dripping, no spray where its been dripping as I drive, spotless.

I bought the truck at 129,000-ish miles and didnt know when the oil was last changed so I did it a few days after purchase and didnt notice any significant amount missing. At 135,000 I changed it again and while draining the oil, it seemed like it quit draining faster than I expected but the oil pan had some oil in it from a previous change and then I changed the wife's oil and drained some back out and then changed the truck oil so I couldnt accurately tell if any was missing. For the last 5000 miles, I tried to check the oil periodically but eventually forgot as the months went on.

For the next 5000 miles, I'm have a little notepad in the truck and going to check it after periods of sitting and at each fill up and keep track of my findings to try and pin point when and how I lose the oil.

Do you guys have any ideas of things to check in the meantime? My current theory is maybe its leaking into a cylinder and burns away slowly enough that it doesnt smoke but not sure if that slow enough of a leak would get 2 quarts burnt off over 5000 miles. Would an average of half quart lost over 1200 miles produce some smoke?

 

Some people have reported that a bad PCV valve can lead to high amounts of oil consumption, that'd be the first place to look.

Is your coolant still nice and clean?

 

+1 on this---from personal experience on a V8 Modular Motor!

Are you using a full synthetic by chance? I've read here were that too can play a part in a loss between changes.

Hope its nothing more severe!

 

Not only the PCV valve but check the hose in the other valve cover check the fitting that the hose is connected to if it can draw air it pulls are through the motor and oil vapor out the PCV valve. On one of my 2000 V10 the glue joint at the fitting was bad (it's 2 pieces).
I use Mobil 1 on my present V10 and only use a quart every 4500 miles.

Denny

 

Denny you're 100% correct----that entire PCV hose and its fittings tend to be problematic. I drive an E-Series so checking all that might be a bit easier from the interior, doghouse removed. The PCV valve itself is quite the challenge since its located just about midway in the tunnel that forms the upper portion of the engine compartment.

 

Im having kind of the same issue, i add almost a quart every 1000 miles, ive always had trucks and theyve always burned some oil and since this is my first v10 i just figured bigger the engine the more it burns lol ill have to check on the pcv now im worried . Last month i added some lucas oil treatment to it and it seemed to help dramatically.

 

Funny, I use plain straight dino oil (Castrol GTX) and never lose a drop...

 

Thats what i use as well

 

I use the recommended MC oil. No problems at all. I have all ways just used the recommended factory stuff. Never had any issues.

 

Sorry guys, I know Im dump
but what the heck is a PCV Valve, where is it, what does it?
Maybe some pics?
I have the same problem of vanished oil, though I lose more then
2 quart.
My water is oilfree, the truck dont smoke, the sparkplugs are fine,
the underside is spotless. So what the hell......
Sometimes it looks like that some squirrels openened the oil cap
and suck it out for what reason.

 

Passenger side valve cover 2/3 the way back, black rubber hose the valve is on the end of the hose that goes into the valve cover. Pull the valve out of the hose and if there is a large amount of oil in the hose your oil is being sucked out of the crankcase as vapor and burned in the motor. Also check the hose on the other valve cover to make sure it's in good shape. If any air is allowed to get into the crankcase from the fitting on the other valve cover, dip stick not sealing or the oil cap not sealing the motors vacuum will suck oil vapor out the pcv valve. The valve is there to burn any vapor that is caused by compression blow by caused be bad rings but if there are any other air inlets it will also pull vapor out of the crank case. I've owned a lot of motors but the Triton family of motor has to be the touchiest when it comes to the crankcase ventilation system. One other thing to do when you have the pcv out is start the motor plug off the pvc valve and rev it up, if a large amount of vapor comes out the hole you have bigger problems than a bad valve like a new motor because of blow by.

Denny

 

Thank you for detailed advice, though I hope that you wont be right with your
black painted thoughts.
The preowner runs out of money, so I have a lot spots, where I have to troubleshoot issues.
Best example is that the complete plastic piece of the driver side valve cover where the rubber hose is fixed on, was complete broken off (2x2") and glued back in with kind of silicone. Really great.
....So now I ordered ASAP a pair of used valve covers, besides the matching gaskets.
Maybe its already the problem......hopefully.

 

My experience is to make sure you replace the PCV valve with Motorcraft not aftermarket. My aftermarket PCV valve failed soon after I installed it. It is not unusual to lose a significant amount of oil through the failure of this part. The good news is that it is cheap to replace.

 

Thanks for all the places to check. It'll give me something to do tomorrow before work. I dont remember for sure what oil but I believe its Ford Motorcraft 5w-30. I buy it in 5 quart blue colored jugs from Wal-mart. I dont know if that's synthetic or not. If the coolant is dark like it has oil in it, then what would that mean?

 

I would say, that your head gasket is already blown or if your lucky, starts to get blown.
Usually you should lose coolant. Maybe you seen white smoke in the rear mirrow when you push the throttle, even if the water temperature is already warm and the exhaust hot and dry inside.
You can control it, if you fill it up till the marker, and control it after one or two days, but be sure to do it at the same water temperature.
Another way would be to remove the water cap and start than the engine, running at idle.
If it makes bubbles at the watercap there will be something wrong.