[SejRamkas]

I just recently picked up a 2016 328d xdrive touring with 98k miles. I'm getting what I believe to be very poor mileage. In a week of driving around town I have not been able to exceed 25.5 MPG while driving like a grandma in ECO+ mode. Keep in mind this is my first diesel car I've ever owned.

I've noticed that the car takes a long time to get up to temp. My average morning commute consists of driving ~10 miles round trip for a total duration of ~30 minutes. During this time the car does not get to temperature and only maxed out around 190F with a 45F ambient temp. Does this sound like my thermostat could be stuck open thus resulting in the car not warming up quickly enough? Am I expecting too much to get 30ish mpg on such a short trip around town and this is normal behavior for the car to not reach operating temp within 30 minutes of driving?

Anything else I should be looking for?

[andreigbs]

If this behavior is not typical, I think you've likely answered your own question

I normally see 32-33 MPG around town average, which is the kind of driving we've been doing mainly since working from home. Before that, longer trips and road trips I would see 35-36 MPG average per tank.

Note that the temp gauge you're looking at is the oil temp, not the coolant temp. But if you're driving around for at least 10 minutes, the oil temp should be coming up to the middle of the gauge.

If you don't yet have it, you may want to invest in BimmerLink and an OBD dongle to check actual coolant and other temps, EGR duty cycle, as well as any error code(s) that may be present.

Then we can hopefully offer more opinions and advice.

[Watsey]

45F ambient is pretty chilly and diesels, especially, typically suffer from poor fuel economy until they have reached normal operating temperature.

The 30d and 35d (I have a 30d) can take 10-15 miles and perhaps 20 minutes to reach full operating temperature. The 28d is obviously a smaller engine than the 30d/35d but the warm-up cycle may take a similar time/distance.

The larger diesels also have an electrically-powered auxiliary heater for the cabin, because of the longer warm-up time compared to petrol engines, and this heater has a high amperage draw which places additional load on the engine thus lowering the economy even further.

I don't know whether the 28d has the same cabin heater, but it may be a factor.

Long story short, 25mpg as a result of short journeys, in cold ambient conditions, and perhaps in stop-start traffic may be on the low side but isn't something that I'd necessarily worry about. At full operating temperature and on longer, steady speed, journeys you should easily see >50mpg.

[SejRamkas]

Originally Posted by andreigbs

If this behavior is not typical, I think you've likely answered your own question

I normally see 32-33 MPG around town average, which is the kind of driving we've been doing mainly since working from home. Before that, longer trips and road trips I would see 35-36 MPG average per tank.

Note that the temp gauge you're looking at is the oil temp, not the coolant temp. But if you're driving around for at least 10 minutes, the oil temp should be coming up to the middle of the gauge.

If you don't yet have it, you may want to invest in BimmerLink and an OBD dongle to check actual coolant and other temps, EGR duty cycle, as well as any error code(s) that may be present.

Then we can hopefully offer more opinions and advice.

I don’t know if this behavior is atypical because I just bought the car a week ago. The temperature I’ve provided is from the coolant temp using an OBD2 Bluetooth reader and the OBDFusion app on my phone. No error codes and initial reading pointed to thermostats failing open causing lengthy warmups. New to this car and new to diesels, but not even remotely new to working on other BMW models.

I drove a mix of interstate and around town driving today for about 15 miles and the car didn’t get warmer than 190F coolant temp in 70F ambient.

[Enabled]

If that's coolant temperature, then 190F (88C) a bit too cold for 15 miles of driving.

I would replace the thermostat with a quality replacement. Even with city driving I get in the 30s mpg with my F31 wagon.




The 328d does have the electric aux heater in the climate box, so it should help with warmup functions.

[andreigbs]

More info is great to have. If all you're seeing is 190*F on the coolant, that's too low for my liking.

+1 on the advice to replace the OE thermostat with another OE-quality replacement.

[SejRamkas]

Thanks for the help guys. Based on a bit of reading I was thinking the thermostat just wanted confirmation. Is there a CEL that would be triggered to indicate the car is not getting to temp or a thermostat failure? I appreciate it fails open to save the engine, but it would be nice if they notified the driver it had failed.

I plan to take it in for a general “tune up” and replace the thermostat and water pump as part of this. Any recommendations on things to check/replace on this engine at 98k miles as part of that?

[Enabled]

Thermostat is mechanical in this car, so there wouldn't be any good way to get an error code for it.

Water pump and thermostat is a good idea.
Check valve cover gasket and other leaks, but at 100k, I didn't have any maintenance to look at on mine.

After 7-8 years old in the heat, the valve cover gasket and some of the oil filter housing gaskets may start seeping. Mine did and they got a replacement.

I'd say that would be more of an age thing instead of mileage.

I'm still on my original thermostat and water pump, so I will do those soon.

[SejRamkas]

Originally Posted by Enabled

Thermostat is mechanical in this car, so there wouldn't be any good way to get an error code for it.

Water pump and thermostat is a good idea.
Check valve cover gasket and other leaks, but at 100k, I didn't have any maintenance to look at on mine.

After 7-8 years old in the heat, the valve cover gasket and some of the oil filter housing gaskets may start seeping. Mine did and they got a replacement.

I'd say that would be more of an age thing instead of mileage.

I'm still on my original thermostat and water pump, so I will do those soon.

I would imagine they could monitor ambient temp, ECT, and drive time/average RPM to set a counter for how quickly it SHOULD heat up with coded in limits, but I guess that's asking too much. I'm just happy theyve had them fail open so as to save the engine...

I know all about BMW valve cover and oil filter housing gaskets unfortunately in my years of owning BMWs.... Dont even get me started on oil pan gaskets... Fortunately this one is possibly just barely weeping as I checked prior to purchase and theres just a little bit of muck on the lip of the head where it meets the valve cover now. No active leak.

[Enabled]

I've owned BMWs of all sorts for almost 20 years (I still have them all!) and haven't had oil pan gasket issues! Weird. VCG and OFHG are the 7 year job, every time.