High oil consumption, but no visibleleaks: on a 2002 Toyota Hilander V-6. I suspect valve seals (vehicle was sitting for several months), but wondered if there was some other possible source. Only one time (after vehicle sat for 3 months)..engine started hard and smoked badly for 2 minutes. This was not evident any other time. Have not noticed oil smoke in the exhaust when starting or running engine any other time. Oil consumption varies: mostly 1 qt per 300-400 miles; but one time on a 350 mile trip there was no oil loss at all. Suggestions are welcome!! Thanks. Dave G.

When the oil level goes down - a lot and it isn't leaking out it must be being burned or otherwise disappearing through the exhaust.

That the oil consumption is high isn't unusual though it is unusual that consumption has been allowed to become so heavy without being repaired, perhaps that was a factor in the previous owner's decision to change his car.

Such a heavy oil consumption would usually cause blue or blue/grey exhaust smoke, though the driver is often among the last to notice it due to the slip stream dispersing it quickly. Try parking your car in a shaded place away from people and increasing the rpm to around 2500/3000 and hold it there for a minute or two...

Heavy soiling inside an engine, including a blocked crankcase breather system, can create conditions that cause high oil consumption but modern engines using modern oil rarely develop those conditions and that leaves oil going upwards bypassing the piston rings or the oil going downwards bypassing the valve stem oil seals - or both being the strongest possibilities.

Both of these are expensive to rectify but if piston rings are to blame the cure is an engine overhaul. Considerably less expensive but still eye-wateringly painful is valve stem seal replacement - and so a mechanic after a few tests would usually recommend this as a probable cure but no promises...

The bad news doesn't end there as high oil consumption usually damages the exhaust catalytic converter and oxygen sensors.

It should be possible for you to buy an oil additive to add to your engine oil. If a bottle of oil seal rejuvenator improves matters it would reinforce the possibility the valve seals are a culprit...

Smoke in the morning is valve stem seals. They leak overnight into the combustion chamber.

Hey Barry, I assume you mean valve stem seals... bad or leaking valve stem seals will manifest themselves as whitish oil smoke from the exhaust as soon as you start the vehicle...after the vehicle has been sitting for a while..especially after the vehicle has been sitting over night. You will notice slight oil consumption..When you change the oil, the smoke will slow for a while.. until the oil gets some milage..then it will start smoking and using oil again.....

Possible cause is several drops of oil are leaking past the valve guide seals when the vehicle just sits. When it is started the oil begins to burn off in the cylinders and after awhile the smoke disappears. I have always recommended cha going the oil to a synthetic and adding an oil additive called Restore. It comes in a cylindrical can in 4, 6 or 8 cylinder size. Put 1 can in with the new oil. Drive the vehicle on the highway for 45 - 60 minutes. I recommend putting on a few hundred Mrs. The additive restores the valve seals preventing the oil from dripping into the cylinders. Have used it on my customers vehicles for 20 years. Saved them a lot of money from replacing the seals.

How many miles on your vehicle ? Do you see any leak spots on the ground from the truck ? Blue exhaust , oil burning , valve guide seals , piston rings , PCV clogged .

Oil Consumption Diagnosis
Checks
Causes
Excessive oil consumption, not due to leaks, is the use of 1 L (1 qt) or more of engine oil within 3 200 kilometers (2,000 miles).
Preliminary
The causes of excessive oil consumption may include the following conditions:
• External oil leaks
Refer to Oil Leak Diagnosis .
• Incorrect oil level or improper reading of the oil level indicator
With the vehicle on a level surface, run the engine for a few minutes, allow adequate drain down time, 2-3 minutes, and measure for the correct engine oil level.
• Improper oil viscosity
Refer to the vehicle owners manual and use the recommended SAE grade and viscosity for the prevailing temperatures.
• Continuous high speed driving and/or severe usage
• Crankcase ventilation system restrictions or malfunctioning components
Refer to Crankcase Ventilation System Inspection/Diagnosis .
• Worn valve guides and/or valve stems
• Worn or improperly installed valve stem oil seals
Refer to Spark Plug Inspection .
• Piston rings broken, worn, or not seated properly
Allow adequate time for the rings to seat.
Replace worn piston rings, as necessary.
Refer to Cylinder Leakage Test .
• Piston and rings improperly installed or not fitted to the cylinder bore
Refer to Lower Engine Noise, Regardless of Engine Speed

You are most likely burning it. There is much less smoke produced these days, with the cat. converter.

A wear area on yoru vehicle is valve stem seals, when they go, oil is actually pumped out...

Also, consider a high mileage blend oil, like casteroil. I am not into mechaninc in a can, but this stuff lowers consumption and is semi synthetic...

You can reaseal the valve stems, but I wonder about guide looseness, and fairly rapid seal failure again...Still, you can get it going and sell the vehicle....

valve seals could be going use valvoline max life it will soften seals but it is just a band aid

HI, the best thing to ensure the right choice of repair is to look under the vehicle and inspect the oil pan and plug. you will notice on site where the leak is during this inspection. Considering the miles on this vehicle, the oil consumption is quite normal. you will have to replace the valve seal and rings soon. most oil consumption will occur around the 90-100,000 mile mark. Most likely, this oil leak will be coming from the oil pan itself but, it always good to inspect it before you buy new parts.

Please rate and god bless:)

next time replace the bearings all ways do that..... now you may have damaged your crankshaft. every mechanic nows to do that
if they dont they want more money

if the car gives white smoke, you may have wornout piston rings