BMW E53 X5 3.0i Fuel Economy Capabilities

[Bayerische E53]

I thought this might interest you guys so I wrote it up!

I recently took a nearly 3,000 mile trip with the X5. At one point I encountered a very long 55mph construction zone where there was absolutely no traffic. I set the cruise control at 61mph. When I did this, I realized that my on-board fuel range calculator kept climbing. And climbing. And climbing. It kept climbing to a point when the distance on my trip meter (which I had reset at my previous fuel stop) and remaining fuel range equaled nearly 650 miles. I then started doing some mental math. If these calculations were correct and I divided them by what I approximated the fuel capacity to be (25 gallons) it yielded me a theoretical 26mpg. “Bullshit,” I thought to myself; “this thing is WAY OFF.” But then I noticed that the remaining fuel range and the trip meter were BOTH increasing at the same time. There came a point where the trip meter and remaining fuel range equaled nearly 665 miles. I then thought to myself, “ok, could this really be plausible? Could I get MORE than 650 miles out of a tank? Could I get 26mpg? Could I get MORE??? (Well, these calculations were a bit off because the tank is actually larger than 24 gallons, but not by much – and there are other variables explained below).

The following thought then entered my mind: “And what about the fact that I had not driven so conservatively since my last fill-up? Maybe, just maybe, could I get 700 miles out of the tank if I drove at a conservative, yet reasonable, speed??? And what about the fact that the fuel range goes to “- - - -“ before the fuel tank dries up? I damn well could get OVER 700 miles out of a tank!

I consulted the econometer to see at what speed the X5 returned the highest mpg. I started playing around with speeds on my cruise control and I found that the X5 3.0i’s “sweet spot” is at an indicated 64.5mph (62.5mph GPS-verified). At this speed, the econometer was at its highest (to the left of the unmarked hash mark). I don’t know what that hash means, but it appears to be 25mpg. The challenge was on. I was going to try to get over 700 miles out of a tank (i.e. over 26 mpg) under “reasonably conservative” driving habits.

Having decided I would test this out, I stopped for the night and planned on getting up really early to beat traffic so I could get as much of an uninterrupted run as possible. Before going to bed, I opened up my owner’s manual to get the precise BMW fuel specifications. I came to find out that my 24-gallon fuel tank capacity was wrong, but not too far off. The manual states that the fuel tank capacity is approximately 24.6 gallons and that the reserve is approximately 2.0 gallons (for the 3.0i – according to the manual, the V8 cars have a 2.5 gallon reserve tank). This equals a total of approximately 26.6 gallons of fuel. That means that if I could find a way to make the tank return the 700 miles I guessed it could earlier in the day, it would mean the car would return a theoretical 26.31mpg. An SUV RETURNING OVER 26MPG?!?!?! Maybe the car computer wasn’t full of shit earlier when I calculated a rough 26mpg (even based on an incorrect 24 gallon fuel tank capacity). Needless to say, I couldn’t believe my calculations. I was itchin’ to get going the next morning to see what would happen. I went to bed VERY motivated to realize my calculations.

For reference, here are the specs of the test mule:

Vehicle: 2003 X5 3.0i
Odometer: 138,000 Miles
Transmission: Automatic
Suspension: Completely Ruined Stock (needs all new bushings, ball joints, and shocks)
Oil Consumption: 1quart/3,000 miles (NOT A TYPO)
Miscellaneous: Aerodynamic inefficiencies such as protruding front left wheel well liner (adds drag and therefore decreases fuel economy)
Cargo: Approximately 100lbs of personal items in the trunk
Tire Pressures: 36psi Cold tire pressure (BMW recommends 39 so I was working the car harder; more friction, more drag, lower fuel consumption – stupid mistake)
Temperature: High ambient temperature reached into the high 90s
Route: Midwest Mountains (constant acceleration/deceleration up/down hills hurts fuel economy)
EPA Official Fuel Economy: 19mpg (highway) (that’s a theoretical 505.4 mile range at the maximum 26.6 fuel tank capacity BMW lists).

I rose at 4am the next morning to brim the tank until it was vomiting fuel and then sorted my tire pressures. My strategy was simple. Slowly accelerate up to speed, take as few pee-brakes as possible, and keep her at the 62.5mph “sweet spot.” (During my econometer testing the day before, I actually noticed that 52.2mph gave a slightly higher fuel economy than 62.5mph, but that’s not a practical speed to maintain on a highway. After all, I want this write-up to be as realistic as possible. 62.5mph is much more reasonable (and realistic), even in 70mph zones. Trust me, it’s actually not bad going 62.5mph in a 70mph zone – I thought I was going to tear my hair out but I was totally fine). With that, I set off.

During this test, I only came off cruise control 3 or 4 times and took 3 breaks. Of course, in the interest of staying realistic, I ran the air conditioning, radio, and charged my phone and GPS all at the same time for the duration of the test. Here are my findings with pictures for proof.

Picture 01: Computer readings shortly after topping up

Picture 02: Climbing

Picture 03: Climbing to a theoretical 666 mile range

Picture 04: Still at a theoretical 666 mile range

Picture 05: Theoretical 686 mile range (COULD THIS BE POSSIBLE?!?!?!)

Picture 06: Theoretical 686 mile range (This is starting to seem possible!!!)

Picture 07: Back down to a theoretical 668-mile range (damnit!)

Picture 08: Back up to a theoretical 680-mile range!

Picture 09: Up to a theoretical 685-mile range!!!

Picture 10: Down to a 671-mile range (the torture!)

Picture 11: Up to 680!

Picture 12: Down to 675

Picture 13: Down to just over 660

Picture 14: Hash marks after traveling 662.7 miles!

Picture 15: Finally, I ran out of balls after coming so close to my goal of 700 miles

Picture 16: I brimmed the tank until it was vomiting fuel again to see how much fuel I had consumed

That’s it – a total of 683.1 miles on a single tank of fuel in an utterly ruined 2003 X5 with tire pressures a bit below spec, A/C on, radio on, and the GPS and Phone drawing power. With a total fuel consumption of 25.59 gallons, that’s an unbelievable 26.69mpg. Having approximately 1.01 gallons left in the tank, I could have theoretically travelled another 26.69 miles for a theoretical fuel tank range of 709.8 miles!

Caveat: to be completely conservative and remove doubt, I’ll adjust the total mileage covered. Because the indicated speed was off by 2mph, it is plausible that the trip computer is off by the same margin (since both readings come from the wheel speed sensors). This means that I may have travelled a slightly shorter distance than the trip computer says (yeah, I didn’t think about verifying the distance via my GPS unit – my mistake). Being that this drive took about 12 hours, I’ll say that there may be a 24-mile distance discrepancy (2mph x 12 hours). Even at such a discrepancy (659.1 miles), the X5 still returned 25.76 miles per gallon.

Once more, think about the mule I used as the test subject and imagine what a perfectly operational X5 could do. I’d be willing to put my money on a solid 27-28mpg even after the adjustments for the wheel speed sensor discrepancy (kicking and screaming, but I honestly think it’s possible). At the consumption volume of this test (25.59 gallons), that’s a potential 716.52 miles – well over the 700-mile range I theorized the X5 could potentially achieve. And that’s adjusted for the speed/distance discrepancy built into the wheel speed sensors!

What a car. What a brilliant motor the M54 is.

I’m a believer.

Note: The server is not allowing me to host any pictures at the moment. Could a moderator please let me know if there's a problem with the server or if it's an intermittent glitch? Thanks!

[brokenbmx06]

I believe under the right conditions almost every car can do pretty damn well. In my 1995 bmw 325i MT5 I got 32 MPG with cruise and a little city traffic over 250 miles. Those are some verry impressive numbers none the less. Inflate those tires and do it again!

[JCL]

Couple of comments.

1) Your tires were not underinflated, they were overinflated. Spec is 32 psi, from memory. The 39 psi figure is if you are cruising over 100 mph (ie autobahn), with a full load of luggage and 4-5 passengers. See your manual.

2) The odometer is not likely to be off. The speedometer is electronically adjusted to overread when it gets the signal from the wheel speed sensor, the odometer is not.

3) The theoretical sweet spot will be the lowest speed that you can hold top gear with the torque converter in lock up mode. It will be lower than what you were running, due to air drag.

4) I didn't see a mention of fuel AKI, but assume it is 89 or 91. Shouldn't matter. However, the amount of ethanol matters significantly. Ethanol will provide a 4% or so mileage reduction due to the lower energy content in E10. Maybe you had ethanol-free fuel.

My 2003 3.0 returned 27.5 mpg (Imperial) regularly on the highway; that works out to 23 mpg for the smaller US gallons. My highway trips include crossing the Coast, Kootenay, and Rocky mountains so I could do better on the flats. I drive for economy just as standard practice on long trips. Our speed limits tend to be lower here so it is less of a struggle than if we had higher limits. I can see that I could have achieved 30 Imperial (25 US), but your figures are impressive.

[Phr3d]

Cain't wait to try this on 5sp M/T - I know the dif between our normal 80mph and the 72mph for our trip was a nice surprise (21.5 incl blue ridge mountains) so I'll check it out - thanks!

[Bayerische E53]

Originally Posted by JCL

Couple of comments.

1) Your tires were not underinflated, they were overinflated. Spec is 32 psi, from memory. The 39 psi figure is if you are cruising over 100 mph (ie autobahn), with a full load of luggage and 4-5 passengers. See your manual.

2) The odometer is not likely to be off. The speedometer is electronically adjusted to overread when it gets the signal from the wheel speed sensor, the odometer is not.

3) The theoretical sweet spot will be the lowest speed that you can hold top gear with the torque converter in lock up mode. It will be lower than what you were running, due to air drag.

4) I didn't see a mention of fuel AKI, but assume it is 89 or 91. Shouldn't matter. However, the amount of ethanol matters significantly. Ethanol will provide a 4% or so mileage reduction due to the lower energy content in E10. Maybe you had ethanol-free fuel.

My 2003 3.0 returned 27.5 mpg (Imperial) regularly on the highway; that works out to 23 mpg for the smaller US gallons. My highway trips include crossing the Coast, Kootenay, and Rocky mountains so I could do better on the flats. I drive for economy just as standard practice on long trips. Our speed limits tend to be lower here so it is less of a struggle than if we had higher limits. I can see that I could have achieved 30 Imperial (25 US), but your figures are impressive.

1) Hrm, I must have read the door jam specs incorrectly. Ok, so strike that one off the list.

2) If that's the case, as supported by one of the posters in this thread who compared it with GPS accuracy, I guess my mpg was truly above 26mpg. Impressive!

3) Right. That's a good point. However, as I said, the 62.5mph "sweet spot" was what I found to be the most realistic and reasonable given average highway speeds.

4) I use 93. The pumps all said "fuel may contain up to 10% ethanol" so there's really no telling. Maybe I had some ethanol in there; which would mean that the fuel economy would be even better with non-ethanol fuel.

5) My trip took me through the midwestern/southern "mountains/hills" of Kentucky and Tennessee. In fact, my highest elevation was about 1,300 feet. So I wasn't on flats the whole time - it was half and half. The remainder of the trip took me through Georgia and into Florida where it is relatively flat. Considering that, as I forgot to do in the original post, maybe the fuel economy could have been EVEN higher.

Oh, and one more thing I forgot to mention. The mule has the original spark plugs and injectors and I don't exactly know the last time the air filter was changed - but I do know that it was over 60,000 miles ago.

Sheesh!

[Green Dragon]

Great write up! I have witnessed on several occasions my '04 3.0 6-speed manual, getting 28 mpg or better on highway. One morning at about 4am coming back from Park City heading home, (lots of mountains) I was able to sustain 30.5 mpg most of the trip home (about 150 miles). It dropped to 28.9 due to a 7500ft mountain pass in a canyon and was snowing. I did not use cruise control and maintained speed near 70 mph (non-corrected.) I "egg-shelled" the throttle and carried momentum as best as possible. Ambient temp was in the teens. I turned it into a game on my way home to help me stay awake. That was the best I have seen on this beast. 10% ethanol with a lucus upper cyclinder blend. Tire pressure at 35 psi.

I woke my wife up when I got home and showed her. She was impressed and laughed at my pure geekness and went back to bed.

My X is not bone stock and has an CAI, Shark injector, and free flow exhaust after the resonator.

I will conduct further tests in the future. I will be adding stainless steel headers and Kw coilovers. Maybe a change in ride height and or rake might lower drag coefficients. I'm also considering changing out my 4.10 diffs for the 3.64 (in the 4.4i). Not sure how that would play out as it changes the optimal torque range to a higher speed. And as we all have figured out, air drag is part of what is killing out mpg's. The one fellow who has done this reported an average increase of 2 mpg's. Not sure yet if I will try this.

Does anyone know if not having the disa valve vane (the flap) present affects your mpg's, efficiency, and or power output? I pulled the Vane last fall as it was failing and the metal cap pin was working itself out and heading for the intake valves. Good thing I caught it.

[TiAgX5]

Totally achieveable. '03 4.4 X5 here, at 70/75 mph I have managed almost 600 miles GPS indicated (the ODO is generous on miles traveled) on a tank. I do the 1100 mile run (GPS again) between FL and TX on 1 stop regularly with 40 miles to E showing on the OBC upon arrival. Zero oil consumption engine but I do mix 10 ozs of Lucas upper cylinder lube in each tank. I laugh when I see the commercial for the Jeep Cherokee and they BRAG how it can go 500 miles on a tank.

[TiAgX5]

I found the ODO in the X was just short of being exact to the GPS distance shown with new, full tread tires full inflation. It would click off a mile about 50ft B4 the GPS would. As the tires wore the 50ft distance has increased to well over 100ft per mile. That condition has shown itself in a overreading of distance on the ODO when compared to the GPS distance after a long trip.

[motordavid]

Good write up, believable info & data.
Have seen 23 on a full tank day trip, but under 'ideal' conditions and less than cop attracting speeds.

Back at the mpg ranch, I would have a difficult time doing our usual 'runs' to NJ/NY etc., at that kind of low(er) speed and the attendant attention/process necessary to obtain better than our 'usual' mpg, trip-wise. Couple that with our high rpm at speed 5 spd manual, and it simply 'is what it is' for us in our '01 X.

For fun/curiosity, I have done some full tank conservative speed/careful driving 'trips' in our '02 VetteVert, and our best was 33 point something, over nearly 600 miles. That car is our 'econo car' in almost any usage.
GL, mD

[TerminatorX5]

the speed is measured in the tire rotation impulses coming from the Hall sensor in the left rear tire (and matched to the other readings).

The '06 E53 X5 4.8iS with the stock 20" staggered tires is measured at:

4229 impulses per km in speedometer
4282 impulses per km in odometer

As the tires wear out, the covered linear distance changes in relation to the rotational distance of 4229 (or 4282 clicks) clicks read by the car systems.

This involves math beyond my sleepy eyes at this time of the day, something like a Pi, tire diameter, blah, blah, blah...

Theoretically it is possible to "calibrate" the speedometer to match the odometer readings by altering the number but I don't know if this will affect any other systems, otherwise functioning properly with the factory values...