M20B25 - Weird occasional oil consumption

[schocca]

I have a really weird oil consumption issue on my 325i vert. The model is a 1989 chromie with 93K miles on the clock.

No problems until this summer. Oil level in middle of the dipstick marks. Went on a work trip (60 miles each way), no problems on the way up. On the way back, the low oil light appeared on the overhead panel.

- A quick stop revealed that the oil WAS now at the lower mark (so the sensor was working). Topped it up to midway again and kept on travelling.

Another 1000 miles travelled without issue over several trips. The oil level did not move a mm on the dipstick and I was driving motorway + fun miles in back lanes (so revs at all levels).

Then, last month, I travelled on a long business trip via the M1:
– Oil at midpoint of dipstick when cold before the trip.
- Travelled just 50 miles and the low oil level light came on again.
- I stopped, topped up and then travelled another 300 miles to finish the trip without further issue.

Any ideas on what could be causing this oil consumption issue?

Many thanks in advance for your thoughts regarding this,

Schocca.

[martauto]

How long did you wait before checking the oil level after stopping ?

Mart.

[schocca]

I waited a few mins before reading the level.

The first time it happened, I just waited and then tried to restart the engine (assuming a dodgy sensor), but the low oil light reappeared and I then waited before reading the level.

Once the oil was topped up, the low level light disappeared...

I’m ok with a car burning oil (I used to drive an old MGB which needed a top up every 100 miles!), but the oil consumption seems random... is there any rubber parts in the oil system that I should look at?

[boiliebasher]

Is there any obvious signs of oil leaks anywhere?!

If not, could be valve stem oil seals. Many of my previous cars' oil leaks were due to the stem seals being past their best

[martauto]

If not, could be valve stem oil seals. Many of my previous cars' oil leaks were due to the stem seals being past their best

A point worth noting but the amount of smoke coming out of the back must have been like electing a new pope , I still think it`s worth waiting at least 30 mins after the car stops.

Mart.

[schocca]

Is there any obvious signs of oil leaks anywhere?!

An M20B25 showing no oil leaks? Hmm, well, where do I start!
- Yes, there is the usual drips and drabs on the garage floor, but nothing new and it's all minor stuff. (I've had my car for 10 years now, so pretty used to it's minor foibles).
- I'm cleaning it up to see where it could be seeping.
- Water is clean and no gunge on the oil cap.
- It DOES run hot and this is being worked on at the moment.

Is there rubber pipework/parts that I should check in the oil system? (I'm more of an electrics/electronics person vs an oily bits person TBH...)

[Brianmoooore]

Only external pipework in the oil system is to the oil cooler from the filter boss.

[schocca]

I'll get that bit replaced pronto then (as it's probably original...).

Is it worth replacing the breather pipe as well?