[rainfall]

Hey guys!

how much are you guys getting on the N55 manual MPG on a highway?
I went on a trip recently and got 22.5mpg on a highway. Felt a little low, but AC was on the whole trip and it was (literally) 110F/43C outside.

I was quite shocked with so low MPG, esp because I drove most of the time at 60mph and 6th gear... I asked my friend who has a B48 330i 8AT, he said he got more like 30mpg on a similar trip.

More horses drink more?

Also, I tried to use the search function and got overwhelmed w/ tuning results... :P My car is bone stock.

[Aspen235]

My b58 manual gets more like 33 us mpg (6.7l/100km) on the highway. The 4 banger will do better and the auto box is also better.
22.5 seems low. The easy things to look at are tire pressure, air filter, 20w oil, spark plugs, no ethanol fuel.

[dradernh]

Originally Posted by rainfall

Hey guys!

how much are you guys getting on the N55 manual MPG on a highway?
I went on a trip recently and got 22.5mpg on a highway. Felt a little low, but AC was on the whole trip and it was (literally) 110F/43C outside.

I was quite shocked with so low MPG, esp because I drove most of the time at 60mph and 6th gear... I asked my friend who has a B48 330i 8AT, he said he got more like 30mpg on a similar trip.

More horses drink more?

Also, I tried to use the search function and got overwhelmed w/ tuning results... :P My car is bone stock.

My take is the A/C and 110° ambient temperature conspired to lower your mileage from the low-30s to the 22.5 mpg that you achieved. Do you know what your tire pressures were during the trip?

In a 12/19 thread on M240i mileage, I posted the comment below describing the mileage I'd received to-date from my M240i. I expect the N55 would be reasonably close to a B58 when it comes to gasoline mileage.

"I get low-to-mid 30s from my MT M240i on the highway. That's when driving at 68-72 MPH with just me in the car and with the tire pressures set to the manufacturer's specification. I get 28-30 MPG if I run the car at 75-80 MPH. At 6,350 mostly highway miles, I've averaged 30.7 overall since new. That was based upon the gallons reported by the pumps and the car's odometer reading."

Those 6,350 miles were probably 90% highway miles.

[1more1]

I got around 28MPG on a trip recently, manual N55 with Stage 1 BM3. Around 120-130km/h average in Comfort mode.

[morphomeman]

A/C at what temperature? The cost increases exponentially with each degree of cooling.
Even so, that is a very low number for that speed and gear.

[rainfall]

Originally Posted by morphomeman

A/C at what temperature? The cost increases exponentially with each degree of cooling.
Even so, that is a very low number for that speed and gear.

I put like 70F (21C), which is like 40F below outside.

Someone had asked about the tire pressure, I think it was calibrated. I remember checking tire temperature in the trip and I think the pressure was normal

[overcoil]

I just did round trip Baltimore to north Philly-area about 120+ miles each way.

Temps range was varied because I left 7:00am and returned mid day with temps in the mid to upper nineties. My tire temp were about 37 front and 44 rear when hot. Eco Mode heading up Comfort heading back. about 2 hours 20-minutes each way and some idling due to construction and Kia Soul blowing-up. My speed going back were high.

I was overall in the low 20's for overall mpg.

[Nickies]

Originally Posted by morphomeman

A/C at what temperature? The cost increases exponentially with each degree of cooling.
Even so, that is a very low number for that speed and gear.

A/C has nothing to do and temperature neither. I have tinted windows, my A/C is always on in any driving condition even in winter. Most of my driving is highway and I have a substantial drop in MPG since about a month.

The only explanation has to do with change in the fuel quality. I was consistently getting 29-31 MPG. Now, 27-28 and my tires inflation is on spec. If I drive just a bit more in town, it even go down to 23-24. I always use Premium from new and I have only 17K with no mods.

Don't look for any other reason than fuel.

[morphomeman]

A/C both cools and dehumidifies the air. Both functions consume energy, which in a car comes in the form of fuel. The more you do both, the more energy you consume. That is why the A/C is reduced in eco-pro mode.
I agree that fuel quality is likely a factor, as is tire pressure, but so is the fact that OP was using the A/C to reduce the ambient air temperature by 40 degrees F.
BTW, driving without A/C is not a solution, since then the windows are open for ventilation, which increases drag, which increases cost.

[jzeiler4]

I don't know about these cars but in the BMW MC world a sudden drop in mileage is almost always traced to a bad O2 sensor.

[aerobod]

A medium sized air conditioning unit on a car such as an F22 will have a capacity of about 6kW or 20,000BTU/hr. In steady state cruising at 96km/h / 60mph the car will be consuming about 11kW of engine power with the AC off on level ground, using 17kW at maximum AC capacity is equivalent of adding 16km/h of speed to 112km/h / 70mph.

The F22 is certainly capable of 30 US mpg at 60mph, but the fuel economy at 70mph shouldn't drop off by more than 1mpg or so. I would say 22.5mpg due to just flat out usage of the AC indicates a problem elsewhere other than just AC usage.

In my experience I can get 7.5 l/100km in our M240i at a steady 100km/h (31mpg) and calm conditions, but it doesn't drop below 8.0 l/100km (29mpg) in high ambient temperatures with blustery winds.

[peteyrx7]

Originally Posted by aerobod

A medium sized air conditioning unit on a car such as an F22 will have a capacity of about 6kW or 20,000BTU/hr. In steady state cruising at 96km/h / 60mph the car will be consuming about 11kW of engine power with the AC off on level ground, using 17kW at maximum AC capacity is equivalent of adding 16km/h of speed to 112km/h / 70mph.

The F22 is certainly capable of 30 US mpg at 60mph, but the fuel economy at 70mph shouldn't drop off by more than 1mpg or so. I would say 22.5mpg due to just flat out usage of the AC indicates a problem elsewhere other than just AC usage.

In my experience I can get 7.5 l/100km in our M240i at a steady 100km/h (31mpg) and calm conditions, but it doesn't drop below 8.0 l/100km (29mpg) in high ambient temperatures with blustery winds.

I don't know the answer but just throwing a couple things out there.

1) Different parts of the country run different fuel blends and those also can change between a summer and winter blend. Perhaps you have lovely CA gas like me. I don't have my 240 yet but i do know I got worse mileage here than when the lived on the east coast when I moved my previous cars. Blends impact mileage to some degree.

2) what's the status of your air cleaner/intake? Blockages/overly dirty filter could impact mileage.

[overcoil]

Just came back on the beltway and had the 235 in Eco Pro and the real time MPG reading on the display between Speedo and Rev-counter.

I get the impression if I cruised at 60'ish-mph and did not included urban driving or idling in backups, I could maybe achieve high 20's or maybe even 30 mpg for an interstate drive.

[TwoTonic]

Seems inline with the fuelly averages

https://www.fuelly.com/car/bmw/m235i

[dradernh]

Originally Posted by TwoTonic

Seems inline with the fuelly averages

https://www.fuelly.com/car/bmw/m235i

Good post – I'd forgotten about fuelly as a source for this sort of information.

I'm on the higher end of M240i fuelly data with 28.9 mpg after 11,953 miles.

[DBinOH]

Just finished a 5 hour drive in the hills of upstate NY. I’ve got a 2016 M235 6MT. Averaged around 29 mpg. I’m pretty careful to fill with 93 oct, but I can’t imagine it dropping that much from octane or AC. Are you sure you weren’t accidentally in Sport+ the whole drive?

[Ajowhan]

Originally Posted by rainfall

Hey guys!

how much are you guys getting on the N55 manual MPG on a highway?
I went on a trip recently and got 22.5mpg on a highway. Felt a little low, but AC was on the whole trip and it was (literally) 110F/43C outside.

I was quite shocked with so low MPG, esp because I drove most of the time at 60mph and 6th gear... I asked my friend who has a B48 330i 8AT, he said he got more like 30mpg on a similar trip.

More horses drink more?

Also, I tried to use the search function and got overwhelmed w/ tuning results... :P My car is bone stock.

More horses do drink more, sometimes exponentially. Rather than the AC, driving habit accounts far larger role in determining mpg.

For example, if Im cruising at 80mph with my shitty CA's gas, I usually avg around 28-29 mpg.

If I do a tad spirited driving, a little bit hard acceleration here and there(10%ish of the way), this easily drop the avg down to 26-27 mpg ish.

If you are flooring it quite a bit here and there, that can easily take it down to 22mpg. (Not saying this is your case, just a possibility for you to scratch out)

[Nickies]

Originally Posted by aerobod

A medium sized air conditioning unit on a car such as an F22 will have a capacity of about 6kW or 20,000BTU/hr. In steady state cruising at 96km/h / 60mph the car will be consuming about 11kW of engine power with the AC off on level ground, using 17kW at maximum AC capacity is equivalent of adding 16km/h of speed to 112km/h / 70mph.

The F22 is certainly capable of 30 US mpg at 60mph, but the fuel economy at 70mph shouldn't drop off by more than 1mpg or so. I would say 22.5mpg due to just flat out usage of the AC indicates a problem elsewhere other than just AC usage.

In my experience I can get 7.5 l/100km in our M240i at a steady 100km/h (31mpg) and calm conditions, but it doesn't drop below 8.0 l/100km (29mpg) in high ambient temperatures with blustery winds.

I completely agree with your observations and I could not say better. There is no benefits to shot off the A/C even in winter and I never did on any cars I have owned in the last 30 years with the exception of my classic Z.

[Nickies]

Originally Posted by Ajowhan

More horses do drink more, sometimes exponentially. Rather than the AC, driving habit accounts far larger role in determining mpg.

For example, if Im cruising at 80mph with my shitty CA's gas, I usually avg around 28-29 mpg.

If I do a tad spirited driving, a little bit hard acceleration here and there(10%ish of the way), this easily drop the avg down to 26-27 mpg ish.

If you are flooring it quite a bit here and there, that can easily take it down to 22mpg. (Not saying this is your case, just a possibility for you to scratch out)

.......And if you go Sport +, this is insane. What is surprising, I get my best MPG with Sport mode at a steady 60-70 MPH and I am driving most of the time over mountain roads.

[Mason Hatcher]

Curious what RPM the six cylinder with the 6 speed manual turns at 60 and 70 mph...

[overcoil]

Originally Posted by Mason Hatcher

Curious what RPM the six cylinder with the 6 speed manual turns at 60 and 70 mph...

235 six-speed right around 2150 rpm at 60mph level ground

[Finn Germai-Yaz]

When I had my 335i I got around 32 ish from Las Vegas to Los Angeles. When I drove it to work (13 miles) I was getting around 35 ish. The 6th gear was really high on those, I believe it's around 3000 rpm.