Which speed in 6th gear (6MT) for best economy?

[BigMacSmallFries]

Any idea using the onboard real-time fuel consumption meter below the speedometer/tachometer at what speed the car achieves it's best fuel economy in 6th gear?

Curious to know where peak efficiency falls.

Thanks!

[Andrew115]

For max fuel economy the speed will vary based on the size of the hill your coasting down. couldn't help myself - sorry for being a smart *ss

[JoeFromPA]

I have found no meanginful difference between 55 and 65mph in 6th for any length of time. However, I've noticed about a 6-7% decrease in fuel economy between 65 and 75mph.

So if you want to hypermile, do 65mph or so in 6th.

For what it's worth, I've gotten 28-30mpg cruising at 70+.

[huatian]

Originally Posted by JoeFromPA

I have found no meanginful difference between 55 and 65mph in 6th for any length of time. However, I've noticed about a 6-7% decrease in fuel economy between 65 and 75mph.

So if you want to hypermile, do 65mph or so in 6th.

For what it's worth, I've gotten 28-30mpg cruising at 70+.

Thats pretty impressive for this car, I can't even break 18 mpg yet. Maybe because i'm still in giddy mode; just wasting fuel like a fool

[Who's on first]

Originally Posted by BigMacSmallFries

Any idea using the onboard real-time fuel consumption meter below the speedometer/tachometer at what speed the car achieves it's best fuel economy in 6th gear?

Curious to know where peak efficiency falls.

Thanks!

20MPH, or 137MPH with clutch pushed in.

[karussell]

Originally Posted by I hate picking user names

20MPH

chuckle for the morning. thanks!

[NavyBeeker]

Based on physics, with all else being equal, I think it would generally be the lowest speed where you can sustain 6th gear (avoiding downshifts)... since the drag from air increases with the square of speed.

Problem is - lots of other variables (traffic, terrain, need to turn, etc) cannot be eliminated usually.

[JoeFromPA]

Originally Posted by NavyBeeker

Based on physics, with all else being equal, I think it would generally be the lowest speed where you can sustain 6th gear (avoiding downshifts)... since the drag from air increases with the square of speed.

Problem is - lots of other variables (traffic, terrain, need to turn, etc) cannot be eliminated usually.

The load on the engine in the selected gear also impacts it. A higher load at 1500 rpms to sustain speed than a lower load at 2000 rpms to sustain speed may mean you want the higher RPM (i.e. higher speed) to get ideal fuel economy.

[saxon]

Originally Posted by JoeFromPA

The load on the engine in the selected gear also impacts it. A higher load at 1500 rpms to sustain speed than a lower load at 2000 rpms to sustain speed may mean you want the higher RPM (i.e. higher speed) to get ideal fuel economy.

this....

if we had access to fueling tables from the computer it would be pretty easy to find out

[ES_TRADER]

im getting shitty gas mileage with my 6mt...280-290 miles per tank...my e92 was getting 270 per tank. i was hoping this car woulld carry me north of 350 per tank

[NavyBeeker]

Originally Posted by ES_TRADER

im getting shitty gas mileage with my 6mt...280-290 miles per tank...my e92 was getting 270 per tank. i was hoping this car woulld carry me north of 350 per tank

Not sure if a difference in tank size? MPG should be better with F8x... but think new F8x fuel tank is around 15.5gals or so? Not that big IMO.

[JoeFromPA]

Originally Posted by ES_TRADER

im getting shitty gas mileage with my 6mt...280-290 miles per tank...my e92 was getting 270 per tank. i was hoping this car woulld carry me north of 350 per tank

Can't speak for your driving style but I put about 14 gallons in my tank routinely and get about 320-350 on a tank before I'm well into the reserve. So about 22.8mpg.

e90 had a slightly larger tank I believe, but at that range you should have been getting 17mpg on the e92. If you are getting 280-290 on your f80, that means you are getting ~20mpg which means you are driving your f80 harder than you drove your e92. Well done sir

[karussell]

Originally Posted by ES_TRADER

im getting shitty gas mileage with my 6mt...280-290 miles per tank...my e92 was getting 270 per tank. i was hoping this car woulld carry me north of 350 per tank

that is very poor fuel economy. maybe you are on the boost all the time

but on mostly highway even with me playing around some i'm over 350 miles on a tank.

[ES_TRADER]

Originally Posted by JoeFromPA

Can't speak for your driving style but I put about 14 gallons in my tank routinely and get about 320-350 on a tank before I'm well into the reserve. So about 22.8mpg.

e90 had a slightly larger tank I believe, but at that range you should have been getting 17mpg on the e92. If you are getting 280-290 on your f80, that means you are getting ~20mpg which means you are driving your f80 harder than you drove your e92. Well done sir

maybe cause i refuse to go into 6th at 40mph?

[ES_TRADER]

Originally Posted by karussell

that is very poor fuel economy. maybe you are on the boost all the time

but on mostly highway even with me playing around some i'm over 350 miles on a tank.

i hit the redline like once a week...i do drive with the AC on almost 80% of the time because i have passengers...i dont know

[solstice]

Originally Posted by ES_TRADER

im getting shitty gas mileage with my 6mt...280-290 miles per tank...my e92 was getting 270 per tank. i was hoping this car woulld carry me north of 350 per tank

That was an unrealistic pipe dream by some unless you only cruise on the hwy which is a complete waste of this car. At 16.5 I'm getting about 1mpg better than my E90 M3 due to what I assume is less losses at lower rpm ( I probably average 2k rpm lower in the F80 ). You can't make energy out of thin air with a combustion engine, the energy content is in the fuel and power is energy. You can limit losses some which the S55 does by making power at lower rpms.

[XRAVE]

Originally Posted by solstice

That was an unrealistic pipe dream by some unless you only cruise on the hwy which is a complete waste of this car. At 16.5 I'm getting about 1mpg better than my E90 M3 due to what I assume is less losses at lower rpm ( I probably average 2k rpm lower in the F80 ). You can't make energy out of thin air with a combustion engine, the energy content is in the fuel and power is energy. You can limit losses some which the S55 does by making power at lower rpms.

I don't think that it is unrealistic. I do about a 50/50 split with highway driving and city driving. I have a pretty heavy foot and get 21 mpg out of my 135i with the n55 engine. That's pretty low, due to my driving. I also have a 6spd mt.

S55 is similar to the n55. Matched with a double clutch, I'm thinking that I'll be getting around the same MPG. 21 mpg x 16 gal fuel tank is about 340 miles.

The F80 is a lot more efficient than its previous model in that it minimizes lost energy a lot more effective and it allows it to have the fuel economy of a 6 cylinder when cruising but have the power of a v8 when under power.

You aren't getting better fuel economy because your are producing more power at lower RPM's. Under load, I would assume that with the 18 PSI at any given RPM, you are using just as much fuel as the out going V8. The only time you are saving fuel is when you are not under boost or low boost such as cruising or slight acceleration.

Not sure if the current S55 jb4 supports it but on the N55 you could actually turn off the turbos (By pass them completely), allowing for better fuel economy when on the highway. Granted it wasn't much, maybe 1-2 mpg, on a 2000 mile road trip it might add up.

[solstice]

You'll get the same mpg out of the S55 if you drive it like your 135i. If you use more power than you do today forget it. And if you don't plan to do that, why not keep your 135i?

However you are correct in that the S55 has less losses cruising and that the main savings are likely there not in the power at lower rpm. A 4 liter V8 has more friction areas for sure and overall losses at any rpm.

[XRAVE]

Originally Posted by solstice

You'll get the same mpg out of the S55 if you drive it like your 135i. If you use more power than you do today forget it. And if you don't plan to do that, why not keep your 135i?

However you are correct in that the S55 has less losses cruising and that the main savings are likely there not in the power at lower rpm. A 4 liter V8 has more friction areas for sure and overall losses at any rpm.

Yea, I didn't get a 135i for fuel economy neither did I order the m3 for low MPG. There's also a lot of other reasons to get an m3 vs a 135i besides power alone lol.

[A418t81]

I averaged 23 in both my 335s and I'm averaging the same in my M3. I skip shift and keep the rpm low when daily driving. The car does see full throttle at least in the low to mid rom range every time I'm in it though.

[BlackCobra08]

As a general rule of thumb, peak efficiency for a combustion engine falls between 40-60 mph. Any faster and your fighting wind resistance, any slower and that's where combustion engines just aren't very efficient.

[Buddy Revell]

Originally Posted by ES_TRADER

im getting shitty gas mileage with my 6mt...280-290 miles per tank...my e92 was getting 270 per tank. i was hoping this car woulld carry me north of 350 per tank

Yup, these are the same numbers I'm getting with my M4 and the same ones I used to get with my E92.