Oil level increasing?

[Danh]

As befits a BITOGer, I am pretty conscientious about checking fluid levels and the like. But this has lead to confusion.

Once or twice a year, the car in question (2008 Mazda MX5) will mysteriously show an increased level of oil in the crankcase. When checked in the same spot, orientation, etc. after sitting overnight, the oil level will almost always be at the full mark, but once of twice per year it will show 4 or 5 ounces above that level. After driving it the next day it will return to the full mark. When it's over-full, it seems to me to have a gas odor, but this could be my imagination.

The two things that came to my mind were 1) coolant/bad head gasket or 2) a leaking fuel injector. The dealer found no evidence of either. I sent an oil sample off to Blackstone, which reported only a trace of fuel (though I suppose it could have "burned-off" before I took the sample).

The dealer suggests a leaking fuel injector it would leak all the time, not just randomly once or twice per year. Plus, the car has no other drivability issues that suggest a fuel injection issue.

So, what is this mysterious addtional stuff in the crankcase? Has anyone had an injector that leaked only infrequently?

Thanks for any thoughts.

 

[Quattro Pete]

How is the oil filter mounted on this engine? Is it possible oil from the filter sometimes drains back into the crankcase?

 

[Danh]

The oil filter is a good thought, but it mounts absolutely vertically. It does have an oil/coolant heat exchanger between the filter mounting plate and the engine, but I can't see how oil randomly escape from that, either.

 

[MinusPrevious]

Maybe leaking fuel down the cylinder walls adding to the pan volume

EDIT: Time for a used oil analysis

 

[Ausfahrt]

Originally Posted By: Danh
I sent an oil sample off to Blackstone, which reported only a trace of fuel (though I suppose it could have "burned-off" before I took the sample).


4 to 5 ounces? I would just shrug it off as an anomaly and not worry about it.

 

[KevGuy]

2 words- thermal expansion

 

[Danh]

Originally Posted By: KevGuy
2 words- thermal expansion


Yeah, but the oil level is checked in the morning on a cold engine. Ambient temperatures could vary by 20 - 30 degrees F, but this would have a pretty inconsequential effect on volume I'd think.

 

[Danh]

Originally Posted By: bigdreama
Originally Posted By: Danh
I sent an oil sample off to Blackstone, which reported only a trace of fuel (though I suppose it could have "burned-off" before I took the sample).


4 to 5 ounces? I would just shrug it off as an anomaly and not worry about it.


Not worry aout it? At BITOG that's just, well, heresy. Though it would make life easier...

 

[MONKEYMAN]

Being a Mazda, you may have a build up of "zoom, zoom". The cure for that is driving more...

Are you doing a lot of short trips? I had an oil sample that came back with fuel dilution when doing a lot of short trips and not warming car up well before getting a sample for Blackstone.

Once I started doing highway trips I started using oil at an alarming rate. I have a Saturn, but some of that may have been fuel burning off.

 

[CourierDriver]

I would check on what went on the nite b 4 and see if your beer supply dwindles significantly during those times of abnormal oil rise, imho. just kidding,,I have no clue either.

 

[yonyon]

Originally Posted By: Danh
The oil filter is a good thought, but it mounts absolutely vertically. It does have an oil/coolant heat exchanger between the filter mounting plate and the engine, but I can't see how oil randomly escape from that, either.


The toilet in my bathroom is mounted vertically as well. Still, it seems that every time I press the lever that lets a bunch of water into the bowl it drains uphill until it is empty. Funny how that works.

I would trust gravity to be more consistent than the ADBV in your oil filter.

 

[CourierDriver]

Originally Posted By: yonyon
Originally Posted By: Danh
The oil filter is a good thought, but it mounts absolutely vertically. It does have an oil/coolant heat exchanger between the filter mounting plate and the engine, but I can't see how oil randomly escape from that, either.


The toilet in my bathroom is mounted vertically as well. Still, it seems that every time I press the lever that lets a bunch of water into the bowl it drains uphill until it is empty. Funny how that works.

I would trust gravity to be more consistent than the ADBV in your oil filter.
lmaorof,,good one.