[CostcoPizza]

Hi All -

Hate to be the cat who joins and immediately asks for assistance, but I'm at a total loss here!

2018 230i 6MT <50k mi receiving low oil light every 500~ mi


I'm stumped because:

• No visible leaks (beneath the car, oil pan, filter housing, valve gaskets, etc)
  
  No burning smell
  
  No smoke at startup nor accelerating at speed
  
  No CELs or warning lights
  
  This engine is not known for oil consumption

The only other symptom is that the car has a slight bit of hesitation and roughness when cold. Nothing extreme, but just enough that seems odd for such a modern engine.

I've changed the oil and did not see anything abnormal. I've heard the oil filter housing can crack internally, but wouldn't that mix oil/coolant? I did not see oil in the coolant and the oil temps stay at a notch below 250.

Thank you for any guidance!

[John in VA]

It could be a faulty oil sender/sensor - are you able to measure the oil during an oil change?

[Kernel Kurtz]

Do not keep adding if it says low but there is no obvious leak or usage! Overfilling can cause damage!

I had a sensor fail on my 07 328i and it kept telling me to add even when I knew it did not need any. You would think BMW would have fixed this failure mode by now. If they can't bother with a dipstick this electronic system has to be rock solid reliable, and it sounds like it is still not.

[CostcoPizza]

Thank you both for the prompt reply. That will be my next step.

I erred on the side of caution both times as I was 250+ mi from home and en route.

Wouldn't a failing sensor be more erratic and not register change? It does have some degree of accuracy as once I add a quart, it goes from min -> max.

[MarcoZandrini]

Could be the PVC diaphragm is bad. It's covered by a 10year/15000 mile warranty. With the engine idling, remove the oil fill cap. Place you hand over the oil fill hole to check for a slight vacuum. If there's no vacuum the PVC could be the culprit.

[XutvJet]

When the PVC goes bad on a B48/58, there is usually a smoke screen coming out of the pipes. Honestly, this doesn't sound good given the level of consumption. There have been numerous B58s that had leaking fuel injectors which caused the oil to get washed off the cylinder liner thus the piston ring cuts through the arc sprayed cylinder liner material. What happens first is heavy oil consumption and then ultimately very low compression. The fix is a new short block The B48 is basically just a B58 with two cylinders loped off and is likely not immune to the same issue. A quick Google search does show B48s having heavy consumption issues.

Also, if the B48 was tuned or was run of really bad fuel and the motor lugged in a high gear with heavy throttle (causing high boost), it's possible that an Low Speed Pre-Ignition (LSPI) event happened which can crack a ringland. A cracked ringland can result in excessive oil consumption and eventual motor failure.

I am talking worst cause scenarios here. I'd first make sure the oil level sensor is reading correctly. The simple test would be to drain and measure the volume of oil that comes out. If the volume is as expected, then you should borescope the cylinder walls and look for vertical scoring. I'd also look at the plugs and see if one looks a lot dirtier than the others and start with that cylinder first. It's not difficult work.

[CostcoPizza]

Thank you both, I was not aware of any of those issues. Wouldn't either of those scenarios XutvJet also display some smoke or oil burning?

Regardless, a new oil sensor has been ordered. I've no trips the next couple weeks and will be draining + measuring the second the low oil warning pops up. Also will check the spark plugs at that time.

[Shirazkhan]

U say it has a bit of roughnes when cold,i would inspect the spark plugs,see if 1or more are fouling with oil.
Next the easiest would be looking down and checking the cylinders/pistons.
Best of luck,hopefully not something big.
What is the mileage?