Strange Oil Consumption

Crazy Dazz · 16-08-2020, 01:17 AM

We have a Nissan Pulsar that has been in the family for several years. It is a 2005 Model, one of the last Japanese Pulsars. It has the QG18DE engine.

Apart from (the known problem of) cooking the crank-angle sensor, its has never missed a beat. But from the day we got it, it has had a weird oil consumption problem. It had done about 75kk when we got it, and now I think is up around 120.
It doesn't smoke, or leak, and shows no signs of burning oil.

Because of this issue, we took to checking the oil daily. It will go for weeks of regular driving without the level dropping. Then suddenly slurp a couple of litres is as many days.
It's not my car, so I can't tie the use to any particular mode of driving.
It's an automatic so doesn't get over-revved.

Now this engine IS notorious for its high consumption. 0.5L/kkm is considered common (and if you consider that the engine only holds 2.5L, then there's a problem.) But I can't find any actually explanation for the high use, or the bizarre pattern.

Any thoughts or ideas on what I should investigate, are most welcome.

raceteam · 16-08-2020, 06:39 AM

Does the usage pattern change at all? The most common reason for sudden apparent oil consumption is a car that gets used for regular short trips, then goes on a longer one and uses a litre of oil. What is happening is not sudden oil use on the longer trip, but the motor gets warm enough to evaporate condensation from the crankcase that it can't do on shorter trips. On each short trip, a small amount of oil is used, and a small amount of condensation appears, so the oil level on the dipstick look unchanged, even though it has dropped a bit. Get the car hotter than it usually gets, all the condensation evaporates again, and it looks like a very sudden drop in oil level.

XR Martin · 16-08-2020, 08:43 AM

Start with the pcv valve.

Crazy Dazz · 26-08-2020, 10:26 PM

Quote:

Originally Posted by raceteam

Does the usage pattern change at all? The most common reason for sudden apparent oil consumption is a car that gets used for regular short trips, then goes on a longer one and uses a litre of oil. What is happening is not sudden oil use on the longer trip, but the motor gets warm enough to evaporate condensation from the crankcase that it can't do on shorter trips. On each short trip, a small amount of oil is used, and a small amount of condensation appears, so the oil level on the dipstick look unchanged, even though it has dropped a bit. Get the car hotter than it usually gets, all the condensation evaporates again, and it looks like a very sudden drop in oil level.

According to many sources on the internet, this engine uses 500ml/1,000km

So no need to change the oil, it burns it too quick.
The problem is exacerbated because it only holds 2.5L.
But I have found no definitive explanation of why.

Quote:

Originally Posted by XR Martin

Start with the pcv valve.

That was one of my thoughts too, but I can't figure out where it is. So many damn pipes going everywhere. At least two running from rocker cover to inlet manifold.

gooseneck · 27-08-2020, 04:35 AM

Does oil come out the tailpipe?

If it does:
PCV Valve
Valve Stem Seals
Bad Oil control rings on the pistons

One thing which could set it off and make the problem repeat itself is vehicle position, if its parked up on a hill does it make it ink? If so then its either PCV valve thats located at the back of the engine that has a faulty spring and is stuck open or Bad Oil control rings or a bad valve stem seal.

A bad valve stem seal is usually a temporary problem though upon startup, bad oil control rings will cause the problem to be random when driving.

A bad stuck open PCV valve will show a sign of oil and dirt stuck all the way through the intake manifold, a visual inspection of that will tell you, clean the intake manifold out and see if the oil comes back. If it does, use either an oil catch can or replace the PCV valve and see if that fixes it.

Bad oil control ring, pcv valve or valve stem will show signs on the affected piston by fouling the spark plug of that cylinder.

I would start by pulling the spark plugs and see if they're fouled by oil.

If position doesn't make it worse:
You'll need a hoist and a really bright flashlight for this.

Hoist the car up and check the entire engine bay of the car for any oil seeping around somewhere. After all of this time it will show up as dirt sticking to the engine. I would be checking front and back main bearing seals and the engine sump seal. If theres oil pouring down the side of the engine then it could be either a valve cover seal gone or a head gasket gone.

My mums V6 1MZ-FE camry has the same problem. We just live with it.

If you depend on this car you could conceivably install a buzzer for the low oil pressure light in the dash so at least you get a visual and audible warning of low oil pressure.

gooseneck · 27-08-2020, 05:10 AM

Quote:

Originally Posted by gooseneck

Bad oil control ring, pcv valve or valve stem will show signs on the affected piston by fouling the spark plug of that cylinder.

I mean to say:

Quote:

Bad oil control ring or valve stem will show signs on the affected piston by fouling the spark plug of that cylinder.

A stuck open PCV valve will affect all cylinders equally.