[ezaircon4jc]

Originally Posted by ice31

Very low MPG, are you driving in manual or D? Does your car have start/stop? What fuel are you using?

Start/stop saves a very marginal amount of fuel. Like in the low 1/10's.

[ice31]

Originally Posted by ezaircon4jc

Start/stop saves a very marginal amount of fuel. Like in the low 1/10's.

Depends on the driving situation, his 16mph indicate that he drives in heavy traffic

[ezaircon4jc]

[ChiNorm]

Using the stop/start in cold climates would certainly prolong the amount of time it takes the motor to reach optimum temperature with a noticeable impact on mileage.

Good call.

[Caldie_so_slow]

If I were you, Id pull the plugs to see if they are fouled. I would also get new O2 sensors. After that, basic maintenance. Service the trans, service the diff and start using premium gas from a reputable gas station if you havent been doing so already.

[Caldie_so_slow]

Throw a valve cleaning in there under basic maintenance and get that car tuned for those aftermarket parts.

[Thecastle]

So I'll actually answer the question.

10MPG seems very low for a 535i, I would suspect either your idling a lot or something is wrong with the car, parking brake stuck etc.... Or the intake has thrown off the air fuel ration or screwed up your MAF and your running way rich. I'd remove the hot air intake. Do you drive with two feet one on the gas and one on the brake? This lowers fuel economy as your always dragging the brakes.

My 2016 550I in heavy traffic was around 18-19mpg.. Stock on summer only tires. I typically get about 23.5 mpg on the highway.. Even my 2019 Ram 3500 Cummins which has the areodymanics of a brick wall and weighs double what your 535i does still gets around 16mpg in houston traffic.

Anyway the basics, beyond is it running right?

1) Make sure your tires are properly inflated
2) remove any excess stuff inside the car
3) don't let it idle, start and drive off
4) drive the speed limit or less.
5) get low rolling resistance tires
6) return the car to stock
7) change the oil to something thinner
8) drive outside of rush our / heavy traffic
9) garage the car in winter to keep it warmer
10) Keep your battery charged, running the alternator hard increases fuel consumption
11) Don't use a/c or electric heated seats
12) Check for bad wheel bearings or brake calipers
13) turn off excess power drains, DRL, Stereo climate control
14) Run eco mode and practice hypermilling.