Where's my oil going?!

Just before Thanksgiving my oil pressure gauge ('02 Ranger, 2.3L) went to 0 and came right back up and then did it again a few minutes later. Got it to the dealer- they did an oil change and only a quart of oil came out. I change it every 5000 miles and have never had to add oil between changes .... I check all the fluids once a month. Since then I've had to add 1 to 2 qts of oil every week (that's about 250-300 miles). The dealer and another mechanic I use checked for leaks- none. No spots in the snow or on the garage floor. No blue smoke out the tailpipe- none. The dealer did find some metal in the oil filter- not a good sign. I suspect an oil control ring failure but if that's the case where's the blue smoke?  What say you?

The catalytic converter will consume a lot of oil before it finally dies.
A bad PCV valve can consume that much oil. Check the spark plugs and see if one cylinder is burning lots of oil.

Diesel Dan wrote:

The catalytic converter will consume a lot of oil before it finally dies.
A bad PCV valve can consume that much oil. Check the spark plugs and see if one cylinder is burning lots of oil.

Thanks for the suggestions. The PCV valve crossed my mind but like most everything on this motor, it's a real PITA to work on, especially this time of year (a heated shop is on my bucket list). Like the thermostat (it's in the side of the block), you just about need a lift to do it.  And the plugs are a pain too- I had to pull the coil to get the back two in.  If we get a good thaw soon (it was -14 the other weekend) I'll take a look at it. If it doesn't break the bank I may have the mechanic near work have a looksee.

It's been a good motor but it's a real PITA to work on- it was designed for transverse FWD applications. On DW's old Escape which had the same engine, it was easy to work on.

Hope you and yours have a great Christmas, Dan.

Thanks, same to your family.

Too bad I wasn't up there yet, we could have thrown it up on the lift and had a look-see.
Was about 50* and raining today with 60* coming tomorrow with 18* on monday, should be interesting with several inches of snow to follow.

I would guess blow by. All depends on the rings really. The compression ring and the oil ring. There are many different ways and in combination these can file providing varying symptoms of loss of oil, or burning oil. Actual visual burning oil is usually an issue with the valvetrain, valve seal

I would perform a compression test on the engine if plug access is humanly possible. General results should be all cylinders should be within 10% of each other. If you find a cylinder that falls beyond 10% of the others a leak down test would be recommended to determine a possible failure from the valvetrain or cylinder, piston, ring, head gasket.

Like has been suggested PCV system have caused oil consumption issues of a multitude of makes and models over the years.

After 3 or 4 thousand miles an oil sample for used oil analysis (UOA) from Blackstone might be a way to scientifically observe what foreign material of interest is found suspended within the oil. This might point to a particular internal component of concern that may lead you down path of locating the offending issue.

Amusing history, to me, because some of the story mirrors why I ultimately replaced the engine in my Tundra. Finding the problem costs as much as buying a used engine so we never did find out the cause and I'm guessing that's the same as the Ranger.
Dex told me that aluminum engine casting sometimes have flaws that show up after manufacture that'll cause oil and water to disappear, or open leaks.

Not mentioned:
Sludge.
The look of the exhaust on a cold start, because the Cat will consume and cover many problems when hot.

shatto wrote:

Finding the problem costs as much as buying a used engine so we never did find out the cause and I'm guessing that's the same as the Ranger.

I crunched the numbers and came to the conclusion it wasn't worth fixing- I traded it at the end of Jan. while it still had some value left. If I still had access to my brother's shop (a lift and parts at cost among other things) chances are pretty good I'd still be driving it. Over the last year or so I've put a fair amount of money into it- upper and lower ball joints, tires all around, muffler, thermostat ($140 for labor alone!), stabilizer bar links. Still needed shocks, rear axle seals and brakes, a/c compressor and at almost 168,000 miles the OEM clutch was getting tired. The oil issue was straw that broke the camel's back .... no sense flogging a dead horse. It might have been simple as a PCV valve but even that on the Ranger requires a lift or at least jacking the truck up- in an unheated, uninsulated garage at -20F ... no thanks.