Where is my oil going?!

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Joined
Sep 2, 2010
Messages
964
Location
Kansas City, MO
Hi friends,

I’ve thoroughly searched here and on the internet, and I remain perplexed with where my oil is going.

- 1994 FZJ80
- 194k miles
- Uses one quart of oil every ~800 miles
- HG replaced by Toyota as PM at approximately 125k miles. Valve guides not done at that time. Never been done.
- No smoke on cold start
- No smoke on warm start
- No smoke when taking off fully warmed up after idling for a while
- No smoke under full throttle acceleration, including transmission kick down and up shift
- No smoke under steady load
- Timing cover oil leak — 1-2 drops on the ground/week
- PCV valve, hose and grommet just changed; old valve was fine
- Throttle body is clean
- Use Amsoil 10w 40 synthetic and Toyota 90915-20004 filter
- Plugs look good
- Valve cover hasn’t been off since HG change; doesn’t leak, miraculously
- Original cats, still seem fine
- Runs great, always has during the 11.5 years I’ve owned it
- Whatever it needs, it gets

I’m sure I’m missing some information that’s helpful to form an opinion, so please let me know what I’m missing. I don’t want to replace rings or valve stem seals if they’re not the root cause. Thank you all for your thoughts, questions, suggestions.
 
Has this started suddenly or has it been SOP during ownership?
 
Try punching the accelerator pedal to the floor at night say while driving steady at 40 mph with a vehicle behind you (headlights on) a few car lengths back and report what you see in the rearview mirror.
 
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Hi friends,

I’ve thoroughly searched here and on the internet, and I remain perplexed with where my oil is going.

- 1994 FZJ80
- 194k miles
- Uses one quart of oil every ~800 miles
- HG replaced by Toyota as PM at approximately 125k miles. Valve guides not done at that time. Never been done.
- No smoke on cold start
- No smoke on warm start
- No smoke when taking off fully warmed up after idling for a while
- No smoke under full throttle acceleration, including transmission kick down and up shift
- No smoke under steady load
- Timing cover oil leak — 1-2 drops on the ground/week
- PCV valve, hose and grommet just changed; old valve was fine
- Throttle body is clean
- Use Amsoil 10w 40 synthetic and Toyota 90915-20004 filter
- Plugs look good
- Valve cover hasn’t been off since HG change; doesn’t leak, miraculously
- Original cats, still seem fine
- Runs great, always has during the 11.5 years I’ve owned it
- Whatever it needs, it gets

I’m sure I’m missing some information that’s helpful to form an opinion, so please let me know what I’m missing. I don’t want to replace rings or valve stem seals if they’re not the root cause. Thank you all for your thoughts, questions, suggestions.
How do you drive? RPM, speed, hills, acceleration.....

Mine uses much more oil when driving 75 MPH+ and when downshifting it goes to 3400+ RPM. I have seen it use 1qt in 200 miles and I have driven the same route keeping it only 65 mph and use no oil.

It's because the higher RPM keeps more oil on top of the head and then the PCV sucks it into the intake.
 
When I first bought mine in 2007 with 81K I stared with Mobil 1, 0W40 and it would burn a quart in 1000 miles. I then tried the 5W40 turbo diesel formula and it went to 2000-2500 per quart. I’ve been running that since.

so have you tried other oils?
 
Can you be sure it's not an external leak that's burning off before it makes it to the ground?
 
Mine leaks about 1qt every 1200. The underside of the engine is always wet, but never a drop on the drive. So your's leaking enough to mark it's spot, it's probably just a seal leak.
 
Have you looked at the inner surface of your intakes? Mine were spotless when I renewed the head (new HG, seals, valve grind, etc). I had to pull the upper intake less than 100 miles later to fix a leaking injector; the intakes (both) were covered in oil. The PCV valve ships too much oil into the intakes for my taste.

These engines really need an intake oil filter to run clean.

Having said that, 800 miles/qt is more than I would expect from the PCV valve, assuming it's new. If your pan seal isn't leaking (and you have only one - lucky you), and you have no other significant leaks, it's your valve seals.
 
The PCV valve ships too much oil into the intakes for my taste.

These engines really need an intake oil filter to run clean.

Having said that, 800 miles/qt is more than I would expect from the PCV valve, assuming it's new. If your pan seal isn't leaking (and you have only one - lucky you), and you have no other significant leaks, it's your valve seals.
^^^^

Agreed. Valve Stem Seals and external leaks will account for most of the oil usage we see.

These engines DO circulate a lot of oil. I have an Oil Separator on mine but it doesn't catch enough in the vapor to be of much concern. A few ounces every 500 miles or so.

Prior to installing new Valve Stem Seals.....I was using quite a bit of oil though. I also have some external leaks.


Oil Separator1.jpg

Oil Sep.jpg
 
... Valve guides not done at that time. Never been done.
It makes a difference. This is the most likely path, and because it gets burned, it goes along with your other no-leaks observation.
 
Try punching the accelerator pedal to the floor at night say while driving steady at 40 mph with a vehicle behind you (headlights on) a few car lengths back and report what you see in the rearview mirror.
My friend and fellow 80 owner followed me for quite a while yesterday while I created all the scenarios I could think of that make an engine that’s burning oil smoke. He said he saw nothing. I’ll try it at night, too, the next time I get a chance. Thank you for the tip.
 
How do you drive? RPM, speed, hills, acceleration.....

Mine uses much more oil when driving 75 MPH+ and when downshifting it goes to 3400+ RPM. I have seen it use 1qt in 200 miles and I have driven the same route keeping it only 65 mph and use no oil.

It's because the higher RPM keeps more oil on top of the head and then the PCV sucks it into the intake.
I do a mix of city and highway driving. I’m a slow poke when it comes to acceleration, even for an 80. It does seem to use more on the highway. I recently drove from Kansas City to Boulder, CO, and back for a wheeling trip. It cruised beautifully at 75-80 mph on I70, but it did seem to go through oil at a higher rate. Still, there was no smoke…

My friend (@rockstate45) who was with me in an 80 with recently-replaced rings and valve seals had to add no oil.

If it’s sucking a bunch of oil in the intake, wouldn’t that produce smoke?
 
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I do a mix of city and highway driving. I’m a slow poke when it comes to acceleration, even for an 80. It does seem to use more on the highway. I recently drove from Kansas City to Boulder, CO, and back for a wheeling trip. It cruised beautifully at 75-80 mph on I70, but it did seem to go through oil at a higher rate. Still, there was no smoke…

My friend who was with me in an 80 with recently-replaced rings and valve seals had to add no oil.
I run the stretch of I-70 between KC and Salina, KS and that's where my example is based. It downshifts and run high RPM up the Flint hills.

The head on mine was rebuilt at 145K and I now have 340K. My valve seals are starting to leak a bit so the oil consumption has come up. I don't see smoke other than at first cold start up in the morning.
 
When I first bought mine in 2007 with 81K I stared with Mobil 1, 0W40 and it would burn a quart in 1000 miles. I then tried the 5W40 turbo diesel formula and it went to 2000-2500 per quart. I’ve been running that since.

so have you tried other oils?
Great point/question! I used M1 5w40 turbo diesel oil up until this last change. I’ve read about how the 1FZ drinks more/less oil depending on what is used. I’m going to try Amsoil 10w30 at the next oil change. Thanks for the info.
 
Can you be sure it's not an external leak that's burning off before it makes it to the ground?
Hmm… No, I can’t positively be sure that’s not the case, but I never smell or see oil burning.
 
Mine leaks about 1qt every 1200. The underside of the engine is always wet, but never a drop on the drive. So your's leaking enough to mark it's spot, it's probably just a seal leak.
How do you know yours is a leak (legitimately asking)? Perhaps that’s the case with mine… Thanks for the info!
 
Have you looked at the inner surface of your intakes? Mine were spotless when I renewed the head (new HG, seals, valve grind, etc). I had to pull the upper intake less than 100 miles later to fix a leaking injector; the intakes (both) were covered in oil.
That I have not done, but I know it would be telling. If that were the case, wouldn’t there be blue smoke coming out the tailpipe?
 
^^^^

Agreed. Valve Stem Seals and external leaks will account for most of the oil usage we see.

These engines DO circulate a lot of oil. I have an Oil Separator on mine but it doesn't catch enough in the vapor to be of much concern. A few ounces every 500 miles or so.

Prior to installing new Valve Stem Seals.....I was using quite a bit of oil though. I also have some external leaks.


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Thanks, flintknapper. Were you seeing smoke before replacing the valve stem seals? That’s what’s really perplexing me — I see none.

Great idea on the catch can. I have one from Jegs; I just need to install it.
 
Thanks, flintknapper. Were you seeing smoke before replacing the valve stem seals? That’s what’s really perplexing me — I see none.

Great idea on the catch can. I have one from Jegs; I just need to install it.

On mine yes....but only upon start up and only after having sat overnight. A slight 'puff' of smoke then gone very quickly.

Oil will seep past the Valve Stem Seals overnight and IF enough.... will produce a small puff of smoke at start up. During driving however, no. No smoke, it was just burning off completely enough in the cylinders.

I was at 316K on my engine when I replaced the seals. An engine with lesser miles might not leak as much.....but assuredly they are leaking some if original.

All of mine were rock hard and only the clearance between them and valve stem was providing any attenuation of oil seepage.
 

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