2009 X5 35d MPG (graph)

[FunfDreisig]

Originally Posted by Thunder22

How are you getting exact readings on fuel levels when you fill up? The mileage is easy, but if your remaining fuel calc is off, your MPG calcs are going to be off. (I guess ignoring the #'s after the decimal point is a solution)

Yes I just noticed that I had let Excel label the mpg to 2 decimal places - DUH. I'll fix that.

Obviously you need an accurate measure of the miles driven and the gallons of fuel consumed. The primary source of error in hand calculated mileage is that each time you fill up you must fill the tank to precisely the same level to get very accurate mpg calculations.

Note: you don't have to completely fill the tank; but you must fill it to the same level as you did the last time. The easy way to do this is to fill your tank using the same pump, set to the same flow rate and let the pump cut off automatically. This reduces the human 'topping it up' variable.

The more gals per fill up the more accurate the mpg. A .1 gal difference on 10 gal produces a roughly .25 mpg error assuming an average of 25 mpg. But at nearly a full tank (e.g. 20 gals), the same .1 gal error only produces a .125 mpg error. BTW .1 gal is the roughly the volume of can of Coke or a single click of most diesel pump handles. So I don't get too fussed about a few tenths of mpg on a 'per tankful calculation.

But the real beauty of the fuel log mpg calc. and graph, is not in the mpg diamonds; its in the mpglong line. The lifetime mpg actually gets more accurate with each fill up. Because over longer distances, the 'fill up' errors reduce to the difference between only the very first and very last fill up. IOW they become negligible

Funf Dreisig

[DSE]

I don't know about BMW diesel engines, but my 3.0 liter gasoline engine got progressively better mileage after several thousand if not more than 10,000 miles. It will be interesting to see how long your your trend line continues.

[FunfDreisig]

Some of you may be interested in the data points for the 35d mpg while towing. The truth is that several of the higher mpg tankfuls include some towing of building materials, etc. for the 3 bay garage I'm building (see photo). But the lowest mpg tankfuls are almost exclusively towing.

All of our towing has been with our heavy duty 5x9 utility trailer w/ electric brakes rated at 5,000 lbs. It weighs about 1,500 lbs empty. A typical tow run includes hauling it empty to the quarry (OBC reads 20-21mpg) and hauling back a couple of tons of sand, gravel, road base etc. (OBC reads 15-18 mpg). Elevation en route ranges between 800-1,100 ft every few miles. I set the CC on 55 or 60mph (which ever is the speed limit). The 35d simply keeps on pulling regardless of the steepness on the hills. A typical weigh-in at the quarry is 6,540lb and weigh-out at 10,860 (net 2.16 tons). A 'towing tankful" includes some lower milage times like leaving the engine running to keep the A/C on in 105 degree heat during loading, hooking up the trailer, etc. And some better mpg segments like to/from the fuel station. So the overall average when towing has been somewhere between 18-21 mpg.

There are two mpg tankfuls that are pure towing (between 3,000-3,500 miles on the graph). We made a 300+mile trip towing our heavy duty 5x9 utility trailer. The mileage during that trip ran a little over 20 MPG. We filled it up when the left, when we got there and when we got home. Ironically the higher of the two MPG/Tanks is the trip back home where we were going up in elevation (sea level->1,100ft) and had a cast iron tub in the trailer.

Funf Dreisig

p.s. for scale the spherical water tank in the trailer holds 550 gal and is roughly 5' in diameter.

[admranger]

Nice info on towing. Not a lot of wind drag with that trailer, just extra mass to move.

Doing the math it looks like your X5 (w/people in it?) weighs in at 5000 lbs (if the trailer weighs 1500). So a fully loaded X5 w/max weight towed behind it would be somewhere north of 11,500 lbs then! Definitely want to tow heavy during the free service period (free pads and rotors!).

Thanks for the info! These diesel engines in the BMWs are quite amazing.

[FunfDreisig]

Originally Posted by admranger

....
Thanks for the info! These diesel engines in the BMWs are quite amazing.

We used our previous E53 2001 X5 4.4i exactly the same way. Both X5s towed this loaded trailer very well. The 35d is a little stronger (diesel torque curve) and a little more stable on the road (possibly due to the E70s slightly longer wheel base and revised suspension). But the big difference is MPG when towing. The 35d wins that contest, hands down

Funf Dreisig

[Texas5]

While the MPG of an individual tank of fuel may be distorted by variations in the exact fill-up level, your lifetime MPG is much less distorted (at some point, below .01 MPG).

FWIW, my manual calcs tend to be about 5% lower than the on board computer readings (approx. 16 MPG combined pretty consistently).

[FunfDreisig]

Here are two updated graphs. They look similar. But one is graphed by miles and the other by date. Note: how the mpg has dropped since cold weather set in.

I suspect this drop in mpg is due to 'winter diesel' having less energy / gallon. But it might also be because the 35d doesn't get up to optimum running temp as quickly. I'll probably never know, since BMW saw fit not to install a basic temp gauge in our 35d. I suspect BMW sees this omission as a 'safety feature', since a temp gauge might be too distracting and we'd be unable to keep our eyes on the iDrive screen where they belong.

Funf Dreisig

p.s. You can find the explanation of how I build these graphs and the very low mileage tankfuls in my previous posts in this thread.

[ABMW]

Over 3,300 miles of combined driving, during the last 40-days, I've averaged 23.7 mpg.

During a 2,800 mile long trip, I averaged 24 even. I was much higher, but during the last 200 to 300 miles, I became a bit more defensive in my driving as I entered the Bay Area corridor requiring my speed to increase and decrease on I-5.

At times I had to pass at 100, and then slow to 60.

There were segments when I was averaging 30 mpg. for 100 mile stretches at 80 miles per hour.

You're getting close to what I am. The last tank, was completely stop & go, and I'm getting 17.2 miles per gallon in San Francisco traffic.

I can make a graph, but the point is, I'm averaging slightly above what you are, it would appear.

70 mph. on the freeway, is the sweet spot for the vehicle and one can attain close to 30 mpg. at that speed. Unfortunately, I just can't drive that slow, and I don't feel it's safe to be passed.

I subscribe to the teachings that it's safest to be the fastest moving vehicle in your given traffic flow, so I drive quickly, but safely.

In any case, 24 to 26 long-term is what I'm approaching. As a side note, I never drive without the AC on, as I prefer arid air to humid air, as a personal preference, so that's probably responsible for 1-mile per gallon. The arid air also cuts down on mold growth, within the ventilation system, here in the Bay Area.

I'll experiment when I'm in dryer So. Cal. weather and AZ. I spend quite a bit of time in both locals.

Anyway, it's the highest rated SUV for mileage that I've seen. The only thing comparable, in its weight class right now is the Toyota Highlander.

It's real world mileage is about the same, but the car's handling characteristics are relatively unstable.

The Mercedes Diesels, are just a tad lower, and again the handling of the vehicles and the interior quality is shocking.

So, for now, I've got to hand it to BMW from a fuel mileage perspective. They're on top of the heap.

Their status there won't last long, but it's fun for the time being. Plus the diesel noise is awesome!

I work in Piedmont, CA quite often, one of the most expensive zip codes in the United States, and I can't tell you how many people have come up to me to ask about the vehicle.

The strange thing is, they've been women, women, with their kids in tow! They're so aggressive and excited that they knock on the window, and I think I've cut them off, but all they want to do is ask about the vehicle!

That's not happened with any vehicle I've owned for some years, and it's kind of neat. Then again, it's made me realize that I'm driving a chick's car! I need the aero kit and some 20" wheels, that set them straight ;-) .

[FunfDreisig]

Originally Posted by ABMW

Over 3,300 miles of combined driving, during the last 40-days, I've averaged 23.7 mpg.

During a 2,800 mile long trip, I averaged 24 even. I was much higher, but during the last 200 to 300 miles, I became a bit more defensive in my driving as I entered the Bay Area corridor requiring my speed to increase and decrease on I-5.

At times I had to pass at 100, and then slow to 60.

There were segments when I was averaging 30 mpg. for 100 mile stretches at 80 miles per hour.

You're getting close to what I am. The last tank, was completely stop & go, and I'm getting 17.2 miles per gallon in San Francisco traffic.

I can make a graph, but the point is, I'm averaging slightly above what you are, it would appear. .....

It's always entertaining to read mpg stories. But as I posted recently in another forum...

"...I would be very careful of reading too much into anecdotal mpg reports which don't spell out the distances, avg speeds, driving conditions, time of year, etc. I could easily (and truthfully say) I've seen in excess of 30mpg with our 35d on 30-50 miles runs here in the Texas hill country. BUT they were on clear fall days at speeds of 55-70mph (AKA ideal driving conditions for a 35d - summer fuel, no AC, no head winds, etc.). The ONLY mpg reports I pay serious attention to, is mpg calculated from a fuel log or from long trips, etc."

IOW show us your data bro'. If you can make a graph, then do it. Averages are not all that informative without knowing the range and amount of the input data used to produce them.

Funf Dreisig

p.s. I really don't care whether your 35d is getting more or less mpg than mine. Just what data you have to support your anecdotes.

[jaaX3]

Here my update:

Here are my stats since inception on November 4, 2009 (odometer units = miles; refill amount = gallons; price per unit = USD):

X5d
Date Odometer MPG Re-fill Amount Price per unit
1
11/16/2009 449 22.93 19.534 2.759
12/1/2009 891 21.95 20.138 2.699
12/9/2009 1392 23.39 21.423 2.659
12/27/2009 1745 18.54 19.042 2.619
1/10/2010 2169 21.05 20.144 2.739
1/16/2010 2544 24.53 15.29 2.739
1/24/2010 2967 22.01 19.218 2.739
2/6/2010 3359 22.41 17.493 2.699
2/19/2010 3815 21.01 21.705 2.699
3/5/2010 4245 21.16 20.319 2.799
3/14/2010 4754 24.25 20.991 2.879
3/30/2010 5171 21.28 19.595 2.859
4/11/2010 5649 23.82 20.068 2.859
4/25/2010 6072 20.66 20.476 2.999
5/3/2010 6552 22.92 20.942 2.999
5/22/2010 6966 20.41 20.28 2.999
Avg Consumption: 22.02mpg
Avg price/gallon: 2.80
Avg price/mile: 0.13
Overall fuel cost: 886.30
Avg miles/day: 35.01

Driving Style: probably a 60/40 split city/highway. Lots of shopping parking lot driving, and 4 trips up to the Rocky Mountains.

Price of diesel is rising on us here in Denver. I've gone to the same gas station every fill-up.

(I don't know how to insert a table...)