[popsicle_3000]

I've got an '07 E92 335i.

This winter (I'm in Australia) I noticed gas mileage was much worse than last year. Two days ago I did a 2hr highway drive in -5 to 2 deg, and oil temp gauge never started moving past the lowest mark of 70 deg. On way back, temp was up to 15deg, and oil temp only rose in town, then dropped down to ~80deg on the highway. It never hit the 100-120 it normally runs at in the summer. On that 4hr drive I only was able to manage 9.5L/100km which is quite poor. I figure it's running the car rich as it's always cold, hence the hit on fuel economy.

Cabin heating works ok. Last time car was running too hot was several years ago and I replaced the water pump then. I don't notice that the rad fan is working all that much differently. It doesn't take that long in cold starts to get back to normal idle.

Earlier in the year it threw a 2EF7 code for the thermostat, but was buried in a mechanics report and I didn't notice it, nor did he mention it.

How can I work out if the problem is the oil cooler running open all the time, or the thermostat?

thanks!

edit: apologies, this is in the wrong area of forum. I can't figure out how to delete the thread, I'm make new post in the proper one.

[The_E92_Fan]

Huh…thermostat code and car not getting up to temp… These cars have water pump thermostats that fail in the open position. You need to monitor your oil and coolant temperatures and report back. Pop the oil thermostat cover off to see what’s inside too.

[popsicle_3000]

I've taken off the thermostat cover. Here are pictures of what was there, and the parts I've taken out. I struggle to understand how those pieces could move in such a way as to open or close the thermostat, but I can't find any pictures of what should be inside it, apart from https://postimg.cc/JGgpBbnF. on that picture it appears that there is something else on the inside that is missing in mine.

Here are my pictures:

[sbmws]

If your coolant comes up to temp but your engine oil takes a long time to come up to temp and then can’t hold that temp in cold weather sounds like your Engine Oil Tstat the part you’ve taken out has failed and is in the always open mode and the oil is always running through the oil cooler

Im pretty sure mine has failed open too but it doesn’t bother too much as I live in QLD so warmer part of Aust

Im assuming you are Vic or Tas?

[popsicle_3000]

I'm in ACT. It's not the temperature that bothers me, it's that because it's running cold, it takes a lot more gas.

I think it's failed open, I really can't see how those parts would allow for any movement based on temperature.

what will be best way to check coolant temp?

[BRG_N54]

Originally Posted by popsicle_3000

I think it's failed open, I really can't see how those parts would allow for any movement based on temperature.

It works like a coolant thermostat. There is a wax filled chamber behind that silver pin in the center of the part you removed. As the oil heats, the pin moves out of the housing and compresses the spring. The large diameter then closes (or opens) oil passages in the thermostat housing, allowing oil to flow down the lines and into the cooler radiator. Your center piece looks a bit different than mine, I do not have the 5 holes drilled in mine.

There are some aftermarket inserts you can get that just let oil flow all the time.

[popsicle_3000]

ah ic. so the cylindrical thing makes the pin expand.

no, I don't want it to flow all the time, it's wrecking my fuel economy