Drove an X5 petrol today. comments !
Discussion
Drove from Bedford to London and back. 4.8 X5 sport. Traffic was light andi really loped along convinced I'd get 30 mpg overall. As hard as I tried the journey recorded 23.1. I really was surprised. I know it's a big engine and poor aerodynamics but at 65 on the motorway to only get 23mpg surprised me.
I was seriously considering buying it, hence the use for the day. I looked well ahead, windows closed, easy on brakes and throttle, kept a distance, rolled up to lights yet couldn't get it to more. Never once got close to flooring it much as I wanted to. I've had a 320 petrol S class and easily hit 35mpg so I was dissapointed.
Neighbor with his lexus LS430 is currently averaging 24.8 mpg mixed according to digital dash readout. Recently drove it to coventry and back from rural northumberland and managed just over 33mpg sitting at 70mph.
Only uses it for social and trips with the girlfriend. His daily driver is a diesel Octavia.
Only uses it for social and trips with the girlfriend. His daily driver is a diesel Octavia.
Engineer here! :P
Long story short, without boring you guys with equations, you've basically two main sorts of "resistance" on a moving vehicle at STEADY speed;
1. Rolling resistance - that is, friction etc from the drivetrain and tyres
2. Aerodynamic drag
Generally speaking, aerodynamic drag becomes more prevalent at higher speeds, and there are different types of aerodynamic drag (skin friction, form drag, (and I've forgot the rest)). The main one that varies from car-to-car is form drag, which increases with the following attributes of a moving car;
a. It's frontal area. That is, if you were to simply stand at the front of a car and take a photo of it, and measure that area. The bigger that area is, the more form drag you will have
b. it's drag coefficient, Cd. In simple terms, this is basically how "aerodynamic" the car's shape is, and lower the number the more aerodynamic it is. Cars are usually in the 0.2 to 0.5 range, with 4x4s more towards the upper end of that.
c. vehicle speed. It sounds obvious, but as the vehicle speed increases, so does the aerodynamic drag on the vehicle. However the crucial thing here is that drag increases WITH THE SQUARE of the speed. For example, if you were to double your speed from say 30mph to 60mph, you would actually increase your aerodynamic resistance by a factor of 4.
I haven't touched my textbooks for a year and a half now, but that's what I remember from the top of my head
Sunny
Long story short, without boring you guys with equations, you've basically two main sorts of "resistance" on a moving vehicle at STEADY speed;
1. Rolling resistance - that is, friction etc from the drivetrain and tyres
2. Aerodynamic drag
Generally speaking, aerodynamic drag becomes more prevalent at higher speeds, and there are different types of aerodynamic drag (skin friction, form drag, (and I've forgot the rest)). The main one that varies from car-to-car is form drag, which increases with the following attributes of a moving car;
a. It's frontal area. That is, if you were to simply stand at the front of a car and take a photo of it, and measure that area. The bigger that area is, the more form drag you will have
b. it's drag coefficient, Cd. In simple terms, this is basically how "aerodynamic" the car's shape is, and lower the number the more aerodynamic it is. Cars are usually in the 0.2 to 0.5 range, with 4x4s more towards the upper end of that.
c. vehicle speed. It sounds obvious, but as the vehicle speed increases, so does the aerodynamic drag on the vehicle. However the crucial thing here is that drag increases WITH THE SQUARE of the speed. For example, if you were to double your speed from say 30mph to 60mph, you would actually increase your aerodynamic resistance by a factor of 4.
I haven't touched my textbooks for a year and a half now, but that's what I remember from the top of my head
Sunny
alfabadass said:
I can get 25-30mpg in 3.0 X3 on the motorway.
If I'm lucky, I'll get 18mpg local driving! Usually 16 :-(
I'm assuming that it has the same M54 B30 engine as my E60 530i; I average 30mpg in this & can get over 40 on a gentle long distance run. If I'm lucky, I'll get 18mpg local driving! Usually 16 :-(
Just goes to show you how much a square body shape adds to increased fuel consumption.
V8Wagon said:
My old 4.2 V8 Audi used to be the same....I never got above 23mpg no matter how delicately I drove it. I abandoned it as a useful tool for the regular Brighton to Glasgow run quite rapidly.
Dunno how these folk get good MPG's from big engine cars.
I managed about the same from my 4.2 A8. It was quite acceptable, given that I loved revving it out, and generally never hung around anywhere in it. Some hypermilers in the A8 club reported getting over 30mpg with the same engine, I don't think I ever saw more than mid 20's out of mine, though I was a little too lazy and indifferent to do the sums! The weight of the car, for a full sized executive, was admirable given the aluminium on spaceframe construction, though that Audi V8 was known for being quite a thirsty engine in an era when no-one really gave a sDunno how these folk get good MPG's from big engine cars.
t about that sort of thing.The thing with the X5's is that they are big, square, ungainly pieces of s
t with a front drag area that would be more in keeping with a Scania HGV than a passenger vehicle. The weight is piled on too; since these Chelsea tractors run and hide at the sight of a mud slick on the road, BMW saw fit to make them more appealing to the school run mums with loads of sound proofing, sat-navs and computers and massive, leaden wheels, which do nothing to help the already considerable bulk of the thing. A colleague of mine changed his lovely CLK 270 for a 3.0 petrol X5 and found that his petrol costs almost doubled on his daily 48 mile commute. Indeed, trading off the sleek and slippery CLK for that daft old bus was a bad move and lasted about three months before it was traded in.
23 MPG, you must have been driving like a nun.
I have
a 4.7 V8 Grand Cherokee in the UK that I average 14mpg or so in
a 4.5 Twin Turbo V8 Cayenne in Dubai (just bought it but expecting to average 10mpg or so)
a 6.0 V8 Corvette in Dubai that averages 17mpg
You're just not trying hard enough lol
I have
a 4.7 V8 Grand Cherokee in the UK that I average 14mpg or so in
a 4.5 Twin Turbo V8 Cayenne in Dubai (just bought it but expecting to average 10mpg or so)
a 6.0 V8 Corvette in Dubai that averages 17mpg
You're just not trying hard enough lol
UrbanLegend said:
I'm assuming that it has the same M54 B30 engine as my E60 530i; I average 30mpg in this & can get over 40 on a gentle long distance run.
Just goes to show you how much a square body shape adds to increased fuel consumption.
This. I have the same 4.8 as the OP in my E61. My long term avg mpg is 24.7 over about 9k which is nothing short of astounding for the performance on offer.Just goes to show you how much a square body shape adds to increased fuel consumption.
Unless you need 4x4 the E61 is a far better option. Bigger boot too.
K50 DEL said:
23 MPG, you must have been driving like a nun.
I have
a 4.7 V8 Grand Cherokee in the UK that I average 14mpg or so in
a 4.5 Twin Turbo V8 Cayenne in Dubai (just bought it but expecting to average 10mpg or so)
a 6.0 V8 Corvette in Dubai that averages 17mpg
You're just not trying hard enough lol
The worst 'I live in Dubai and have lots of money' post ever...I have
a 4.7 V8 Grand Cherokee in the UK that I average 14mpg or so in
a 4.5 Twin Turbo V8 Cayenne in Dubai (just bought it but expecting to average 10mpg or so)
a 6.0 V8 Corvette in Dubai that averages 17mpg
You're just not trying hard enough lol
Thankyou4calling said:
Drove from Bedford to London and back. 4.8 X5 sport. Traffic was light andi really loped along convinced I'd get 30 mpg overall. As hard as I tried the journey recorded 23.1. I really was surprised. I know it's a big engine and poor aerodynamics but at 65 on the motorway to only get 23mpg surprised me.
Christ, the old X5 V8 I drove between Williams F1 & home used to get down to about 11mpg!!!!Gassing Station | General Gassing | Top of Page | What's New | My Stuff