MPG Dropped Substantially

Jacksawyer · 05-06-2023, 07:55 AM

i have a ‘m235i xdrive DCT with 90k miles that recently is showing much worse mpg (before 32/23, now 20/15). There are no fault codes present based on both the dealer and bimmerlink diagnostics. i’ve ran a can of 44k, changed the spark plugs and had the dealer perform fuel injector service whatever that is (i probably wasted my money). I think the worse mpg is due to bad o2 sensors but wouldn’t that throw a code or trip a engine light? It is performing fine, except for the lower mpg. Appreciate any feedback. Thank you.

Breakfirstfinishlast · 05-10-2023, 08:08 AM

Either there's mad carbon on your intake valves because of the mileage, or you got a bad case of lead foot going on. Maybe both.

overcoil · 05-10-2023, 08:47 AM

After a highway run coast to a stop / no brakes / use an infrared - red : laser : inexpensive gun and shoot temps of caliper and disks.
Making sure you don’t have dragging brakes.

You can even shoot temps of f&r diff - but not sure how that is diagnosed

05-06-2023, 07:55 AM	#1
Jacksawyer Registered 0 Rep 2 Posts Drives: ‘16 M235ix Join Date: Aug 2021 Location: East Orange,NJ iTrader: (0) Garage List 2016 m235i xdrive DCT [0.00] [0.00]	MPG Dropped Substantially i have a ‘m235i xdrive DCT with 90k miles that recently is showing much worse mpg (before 32/23, now 20/15). There are no fault codes present based on both the dealer and bimmerlink diagnostics. i’ve ran a can of 44k, changed the spark plugs and had the dealer perform fuel injector service whatever that is (i probably wasted my money). I think the worse mpg is due to bad o2 sensors but wouldn’t that throw a code or trip a engine light? It is performing fine, except for the lower mpg. Appreciate any feedback. Thank you.
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05-10-2023, 08:08 AM	#2
Breakfirstfinishlast New Member 9 Rep 26 Posts Drives: 2015 M235i, e36 M3 Enduro Car Join Date: Apr 2022 Location: Pennsylvania iTrader: (0)	Either there's mad carbon on your intake valves because of the mileage, or you got a bad case of lead foot going on. Maybe both.
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05-10-2023, 08:47 AM	#3
overcoil Major General 3074 Rep 5,577 Posts Drives: M235i 6spd Join Date: Dec 2013 Location: Mid-Atlantic iTrader: (0)	After a highway run coast to a stop / no brakes / use an infrared - red : laser : inexpensive gun and shoot temps of caliper and disks. Making sure you don’t have dragging brakes. You can even shoot temps of f&r diff - but not sure how that is diagnosed
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