[TuffLittleUnit]

Originally Posted by Nahoa

A friendly plea that we keep this forum about cars and not politics. We can go other places to espouse and debate our political views. Would be nice, to me, just to talk cars here. Call it a middle ground of BMW lovers of all political persuasions . . .

Sorry - I was having a laugh. Politics ain't my thing. Judd's response was in the same ironic vein and made me giggle.

I'll get my coat...

[ando]

I have a 35i and I am mostly in the suburbs driving short distances pretty aggressively and at 18.5 but still have less than 1,000 miles.

[Nahoa]

Apologies, then, I guess that sailed right past me!

[Lotus7]

X3 35i
Total mileage to date: 480
All numbers are via the car's trip computer except as noted below.
Fuel was whatever BMW fills them up with for the first 250 miles, then filled with Shell V-Power 91 octane w/10% ethanol. That fuel typically gives about 4% less mileage than a non ethanol mix, but unfortunately, that's what we have here.

First 200-250 miles or so were all very low speed suburban driving some of it in snow, rarely getting above 40 mph, engine rarely saw 2000rpm.
mileage = 16.9 Avg. speed=20.2 Temps, always below freezing.

Today I took it on a short trip on a tollroad. No stops on the tollroad for 90 miles, light traffic held it at a constant 64 mph via GPS, plus another 6 miles at 35-45 mph on suburban roads with only a few short stops. Outdoor temp. at start = 43deg. F. and gradually got colder.
mileage= 28.6 (I know it's hard to believe, but I swear that's what it read.
Avg. speed = 52.2 mph

I also checked the distance and speedo error as compared with a very accurate GPS.
At a 65 mph indicated, the actual speed is 63.4 mph (speedo reads 1.6 mph high@ 65) The odometer reads 91.3 miles for an actual distance traveled of 90 miles. (about 1.5% high)

I am carefully logging fill-ups so after a few more tankfuls, will know if the trip computer figures actually match the real amount of fuel being consumed.

[e90diesel]

Wow 28.6 mpg under the conditions you described is impressive. I am looking forward to seeing more numbers as you continue to enjoy your 35i.

[Lotus7]

I didn't have a camera handy to take a pic of the trip computer screen showing 28.6 mpg, but I still have the screen for the return trip:

90 miles of tollroad, this time more traffic and speeds varying from 55 occasionally, to 75 most of the way, plus 15 miles of suburban and local roads @ 30 to 45 mph with plenty of stops. So I'd call it 80% highway, 20% city.

Avg. speed down to only 40.3 but mileage still pretty nice at 24.7mpg overall.

[sfax]

Originally Posted by Lotus7

I also checked the distance and speedo error as compared with a very accurate GPS.
At a 65 mph indicated, the actual speed is 63.4 mph (speedo reads 1.6 mph high@ 65) The odometer reads 91.3 miles for an actual distance traveled of 90 miles. (about 1.5% high)

Doesn't this depend on the terrain? i.e. going up and down a lot will give you a longer distance than your GPS reading? Or does it cater for this as well? Surprised the distance measured is so different

[Lotus7]

This was a long, almost straight stretch of road with almost no elevation change at all (not more than 20-30 feet). I think that slightly optimistic odo calibration is not unusual, plus as the tires wear out, the diameter can decrease by as much as 2.2%. This will add to the already optimistic reading since the total tire revs., the speedo reading and the odo reading will then increase.

Also, tires of the same marked size from different manufacturers can easily vary in the number of revs./mile by 2 or 3%. A ¼ inch difference in tire O.D. on tires of the same size is common. That’s why it’s never a good idea to mix different brands of tires on the same vehicle.

I think that if the total error is less then 5% or so the manufacturer will consider it to be within “normal manufacturing tolerances”.

I have a factory maintenance manual for a old Corvette I once owned that had the (mechanical) speedometer calibration specifications. It is +6/-0%. (It's OK to read high, but never, never OK to have the speedo read low.).

I'm sure BMW would not want to be held libel for anyone's speeding tickets because of speedo's that MIGHT read low, so they add a few % bias to compensate for any combination of tolerance build-up and tire variance.

[sfax]

Originally Posted by Lotus7

This was a long, almost straight stretch of road with almost no elevation change at all (not more than 20-30 feet). I think that slightly optimistic odo calibration is not unusual, plus as the tires wear out, the diameter can decrease by as much as 2.2%. This will add to the already optimistic reading since the total tire revs., the speedo reading and the odo reading will then increase.

Also, tires of the same marked size from different manufacturers can easily vary in the number of revs./mile by 2 or 3%. A ¼ inch difference in tire O.D. on tires of the same size is common. That’s why it’s never a good idea to mix different brands of tires on the same vehicle.

I think that if the total error is less then 5% or so the manufacturer will consider it to be within “normal manufacturing tolerances”.

I have a factory maintenance manual for a old Corvette I once owned that had the (mechanical) speedometer calibration specifications. It is +6/-0%. (It's OK to read high, but never, never OK to have the speedo read low.).

I'm sure BMW would not want to be held libel for anyone's speeding tickets because of speedo's that MIGHT read low, so they add a few % bias to compensate for any combination of tolerance build-up and tire variance.

The speedo argument makes sense actually. Better to err on the side of reporting a greater speed than you are actually doing. Hadn't thought about the effects of changing tyre diameter either.

I knew you would have some pretty impressive technical knowhow on this subject Lotus

[Lotus7]

X3 35i
At the pump mileage update.
For the first (2) fill-ups my mileage was:

First fill-up +263 miles, 15.1 US gal. = 17.41 mpg. (all low speed stop/go city driving)
Next fill-up +158 miles, 8.0 US gal = 19.75 mpg. (30% highway/70% city)

Overall real (at the pump) average mileage = 18.23 mpg.
The odometer/computer display is reading 17.5 avg. mpg at an average speed of 19.4 mph. so it's indicating a slightly poorer fuel consumption than I'm actually seeing.

[xDrive35i]

So, still driving only in the city, did a trip computer reset right at the pump, driving at engine speeds no faster than 3000 in 5th and 6th, and 2000 in 8th; from 1st to 4th, the engine will make its way to 4000 in stop-go and red-light drag races with stubborn cab drivers.

I have about 420 miles on the car (Point A to B to C to Z are not even a chore distance). I'm getting 13.2 mpg. I haven't broken the break-in period rules, i checked the manual. Why, still, am I getting such poor mileage?

[Nahoa]

How far do you drive at a stretch? What temps have you had? What are your road speeds and how far between stops for lights? How much competing with cabbies? If all of those things are short, the temps are low, the engine is cold, and you need to bolt to change lanes in front of the cabbie, that may be what we're going to get for mileage.

Seems to me that the Sport mode actually does better in the surging traffic than the Normal mode does. Maybe it delivers the needed torque sooner to get us up to that short jump speed? Could be wrong here, but that's been my initial impression.

I just crossed 1200 miles and have 20.0 over the last 10 days or so. It moves up and down during stretches of unimpeded freeway and stop and go traffic. In my commute I move well at the beginning while the vehicle is warming, then hit some freeway pulsing between 45 and 70 covering 20 to 30 minutes, then run into serious stop and go for 20 to 40 minutes. On the days off I'd taken trips of 20-30 miles one-way with mostly freeway between 55 and 73, probably averaging 65. Stopping for a couple errands within a few miles of each other. Stoplights every .25 mi to mile in those areas, but no stop and go.

Don't know if that description gives a good enough feel for the driving to compare. Hope so.

[xDrive35i]

Originally Posted by Nahoa

How far do you drive at a stretch? What temps have you had? What are your road speeds and how far between stops for lights? How much competing with cabbies? If all of those things are short, the temps are low, the engine is cold, and you need to bolt to change lanes in front of the cabbie, that may be what we're going to get for mileage.

Seems to me that the Sport mode actually does better in the surging traffic than the Normal mode does. Maybe it delivers the needed torque sooner to get us up to that short jump speed? Could be wrong here, but that's been my initial impression.

I just crossed 1200 miles and have 20.0 over the last 10 days or so. It moves up and down during stretches of unimpeded freeway and stop and go traffic. In my commute I move well at the beginning while the vehicle is warming, then hit some freeway pulsing between 45 and 70 covering 20 to 30 minutes, then run into serious stop and go for 20 to 40 minutes. On the days off I'd taken trips of 20-30 miles one-way with mostly freeway between 55 and 73, probably averaging 65. Stopping for a couple errands within a few miles of each other. Stoplights every .25 mi to mile in those areas, but no stop and go.

Don't know if that description gives a good enough feel for the driving to compare. Hope so.

I mean, I rarely drive more than 5 miles at a time, but after a mile the oil temperature reaches about 240 F and stays there. There are about 8 blocks to a mile here in Chicago, more or less.

It's more than just the cabs...I find myself beating out really almost everyone when a crosswalk decides (or I designate it) to be a starting line. I have no patience for slow drivers. I have no patience for Chevy Suburbans filled with drunk teenagers from Deerfield, IL. I have no patience for buses, cabs, livery vehicles, you name it. There's a lot of that going on.

I'm now only at 515 miles, and I picked up the car two weeks ago yesterday, so I've been careful about using the sport mode of the transmission, and when I select sport on the DDC, I set it so it only adjusts the chassis and steering, not throttle response and shift/engine timing. I envy your 1200 mile mark. This car is so tempting. And because torque peaks from 1200-5000 rpms (and I still havent gotten to 5000), it doesn't seem like the sport mode is really needed for anything other than shift timing.

I'm only troubled because my 2008 535xi Wagon was getting a consistent (albeit unfortunately, still) 14.4 mpg, and BMW claims this 8-speed transmission and new single turbo twin scroll engine make the car more efficient than with my wagon's N54. The X3 weighs about 150 pounds more, and I'm still getting 13.2 mpg.

[Lotus7]

Originally Posted by juddholland

... but after a mile the oil temperature reaches about 240 F and stays there. T...

It's more than just the cabs...I find myself beating out really almost everyone when a crosswalk decides (or I designate it) to be a starting line. I have no patience for slow drivers. I have no patience for Chevy Suburbans filled with drunk teenagers from Deerfield, IL. I have no patience for buses, cabs, livery vehicles, you name it. There's a lot of that going on.
....

We're in the Chicago suburbs (not Deerfield), so have the same daily temps. as you. In our suburban driving, it takes about 2.5 to 3 miles to get the oil temp gauge to move off of "160" and then another mile or so to reach "230-240" so our car is certainly warming up a lot slower than yours. I'm driving in the "Normal" "D" setting, not yet using "Sport" mode, rarely seeing more than 3K on the tach and probably not using any positive pressure from the turbo yet. Out here in the 'burbs' that's more than enough to keep up with traffic. Still seeing 17-18 mpg under those conditions.

From your last paragraph, your low fuel-mileage sounds like it's most likely a result of the number of rapid starts and your admitted impatience with slower drivers. The rapid oil warm-up echoes that probability.

The N55 engine is capable of developing full boost from only 1300 rpm to eliminate any significant turbo lag. On a previous Subaru Legacy GT (high-boost turbo) Limited I once owned that had a real-time fuel consumption digital readout as well as an electronic boost gauge, it was quite sobering to see the fuel consumption readout drop from 12-15 mpg at partial throttle to 2 mpg at half throttle or more when under full boost acceleration. Every half-block 0 to 40mph “Stop-light Gran Prix” costs as much as a half-mile of light throttle cruising.

I’m not suggesting that you change your driving habits, but only trying to explain why your mileage is on the low side.

I have another vehicle that weighs 30% of the X3 (1400 lbs.) and has an engine that only makes 172 HP. Its usual gas mileage is only slightly better (22-24 mpg) than the X3 and I know it’s because of the (entirely different) way I drive it.

Also, consider that your 535xi is fully broken in and the X3's N55 is probably still "tight" and not working at its ultimate efficiency yet. Also, the fuel mileage readout on either vehicle may not be accurate. My X3 digital readout surprisingly reads about 3/4 to 1 mpg lower than the actual mileage measured by recording odo readings and fuel used at the pump.

[RockyMntX35i]

Mixed driving here in Golden / Denver. 23.2mpg

[Brutus1]

FWIW the PC instructor said not to get over 4500 rpms nor to use the cruise control for the first 1500 miles.

[Nahoa]

juddholland, your engine does seem to warm up a lot faster than mine. I can drive a whole two hours and not get to 240 (if I'm remembering right that 240 or 250 is center on the gauge, yes?) on the colder, windier days. On a 45 degree day it's taken at least 5 miles to reach that temp. Don't know if that's significant, but it seems different, for whatever that's worth.

Sport changes the steering and the suspension considerably. Maybe not so noticeable in your current driving. Try it on a curvy road sometime. It also keeps the revs up higher, so isn't just shift timing it also changes how ready torque is.

[JamesBimmer]

Just traveled over 500 miles on the highway and averaged 28.5 in a 28i. Used the cruise control quite a bit (just saw that might be a no no for break-in)

[Bimar]

Anyone on 17" tyres? Are you closer to the listed mpg for your car?

[Nahoa]

Mine continues at 20 over a mixed freeway, stop-and-go, and city commute as well as general errands in the suburbs.

[SMTM]

Originally Posted by inamik75

Anyone on 17" tyres? Are you closer to the listed mpg for your car?

I have the 17's

First tank all city: 19.7
Second tank all city: 19.1

[Lotus7]

35i last fill-up:
All suburban driving. Mostly between 30 & 45 mph with stops every i/4 to 1/2 mile.Mostly in gears 1-6, rarely make it to 7 or 8.
Shell V-Power 93 octane
Mileage measured at the pump = 17.33 mpg (US gal.)
Average speed=21.4 mph