[jtyree]

All;
I have a 2018 328d and it has the same engine as my former 2014 328d. I'm guessing it part of the emissions system, but it seems my 2018 does not get as good of fuel mileage as my 2014 did. Things that I have done on the 2018 like the 2014 model:

1. I have changed out the stock air filter for an AFE dry filter--it helped some.

2. I also tried an oil catch can on it but it set off the PCV sensor.

3. I want to try the AFE cone filter with air box on the '18 but the PCV hose and air intake pipe seem to be mated permanently. In my mind I believe the two will disconnect but I can't seem to find any diagram or video that will allow the connections to separate.

4. I used 6-8 oz of Cetane booster last summer and held around 47 MPG. It was hot here in Texas and now that the weather has cooled some, I'm averaging about 42 MPG. I know with cooler weather comes a drop in MPG on a diesel, but my '14 did not drop that far.

5. I believe I can get more MPG out of the '18 than advertised--I did on the '14 model.

6. Is there any performance chip that I can obtain to increase my MPG on this 2018? I'm not asking the dealership when I go for maintenance. None of the service reps seems to have clue about Mangnuson-Moss as they feel an aftermarket filter will mess up a warranty. One even seemed dumbfounded when I mentioned a diesel "technically runs on air" to function correctly.

By default this engine produces a lot of power, especially torque for it's size. I'm not looking to add horsepower, just get the most I can from the diesel going thru the injectors.

Any help/suggestions that anyone can give will be greatly appreciated.

Thank you.
John

[Enabled]

In terms of engine hardware, the cars are essentially identical.

Stock intake and fresh air filter are plenty for these. The filtration is not going to make a difference. It's a cold air system and it's not like it's having trouble taking air in, even on full 'throttle'.

How many miles on each?
Same exact setup? Same exact car?
For example, the awd cars will have lower mpg.



KermaTDI tune will give you a 2-3mpg bump easily, on both. It's well documented.

[FaRKle!]

Originally Posted by jtyree

All;
2. I also tried an oil catch can on it but it set off the PCV sensor.

3. I want to try the AFE cone filter with air box on the '18 but the PCV hose and air intake pipe seem to be mated permanently. In my mind I believe the two will disconnect but I can't seem to find any diagram or video that will allow the connections to separate.

Do you have a pic? I have an LCI too (MY17) car and didn't have any issues putting an oil catch can in.

[AlpineX]

14 and 15 is rated at just higher mileage than 16+.
Are you comparing rwd sedan to rwd sedan?

For mpg issues, check your oxygen sensors function and regeneration intervals. sounds to me like everything is happy and your mpg is totally fine if you are over 40.

Little things you can do include lightweight wheels and low rolling resistance tires at higher pressure, ecopro, tune, ideal speed etc.

[agentorange]

Does the 2018 have 19" wheels and the 204 18s or smaller ? How many miles on the 2018? Maybe it still needs some break in.

[RJR82]

depending on milage, lower not a worry but about 40k -50k plus i would clean your MAP sensor and your MAF sensor, they tend to gather dirt and can effect mpg