Fuel consumption. Another observation vs E53

[gen2c4s]

We now have 1100 miles on our 30d m sport and to be honest I feel slightly mislead by BMW. The suggestion is that the new gen X5s are a)cleaner (cant dispute that as I have no way of measuring) b) more effecient, I do dispute this, I tried to drive our car as gently as I could and at 55mph I did see 34mpg on a flat peice of road, as soon as there was mild throttle input this dipped to 29 mpg, then around town this soon dipped to 23mpg. At motorway speeds I see 29mpg. My old e53 managed 34mpg at motorway speeds and at 55 mph and 26 mpg round town. Speed wise there is very little difference so BMW can you please tell me how the E70 is more effecient for me?. No matter which way you cut it my old one was more economical.
One other suprise is that I can actually get 23 mpg out of my Gen 2 C4s around town, so BMW well done you have created a mid range SUV that is actually less effecient, to me, than a mid range sports car. Congratualtions!!!

[Fraser]

Manufacturers are getting better at 'cheating' the official EEC fuel consumption tests. BMW may be bad but it's not alone. Chief offender: Toyota/Lexus with its petrol-electric hybrids

[XXX555]

Compare apples to apples: the e53 weights how much and puts out how much HP/Torque and has what interior volume? A heavier, larger vehicle that accelerated faster e70 but uses the less fuel relative to a smaller, "slower" vehicle e53 may be BMW's angle here.


BMW may simply look at how much fuel into the engine puts out how much energy and that the e70 is simply more efficent.

This may be the dynamics part of their efficent dynamics baloney.

[Fraser]

Remember that the EEC fuel consumption test that's used in Europe and in much of the world, and is similar to the EPA test used in the USA, is a simulated test. The vehicle in question isn't driven on the road but is put through simulated driving cycles on a rolling-road dyno. The driving cycles simulate 'urban' and 'extra-urban' driving via a series of accelerations, decelerations, constant speed running, idle periods etc. The test wasn't devised by BMW, or any manufacturer for that matter, it's the work of government bureaucrats designed to 'help' the consumer. So when BMW says it cars get Xmpg or use X litres/100km, this is simply the figure it achieves in the relevant EEC or EPA test. BMW, like all manufacturers, goes out of its way to say that real-world fuel consumption will vary from these figures.

[Penguin]

Originally Posted by Fraser

The test wasn't devised by BMW, or any manufacturer for that matter, it's the work of government bureaucrats designed to 'help' the consumer.

True, but once the manufacturers know the cycle, they do tend to tweak the powertrain programming a bit to get good results on the specific cycle.

One year in the past, BMW motorcycles had a bit of a flat spot at a certain RPM, as knowing the placement of the microphone in the European driveby noise test, they tailored the engine controls a bit so that it was not quite as loud as it passed the microphone. Obviously there is a limit to what the manufacturers will do, as if they tweak it so much that driveability and performance are too adversely affected it will cause customer dissatisfaction, but if CAFE fines are at risk, or they find they have made a mistake and need a quick fix, as in the noise problem on the BMW motorcycle, they might tweak it a bit much. It is pure speculation, but I have heard some people question whether some of the transmission lag or jerkiness might be related to such "test cycle tailoring."

[Fraser]

Originally Posted by Penguin

True, but once the manufacturers know the cycle, they do tend to tweak the powertrain programming a bit to get good results on the specific cycle.

That's exactly what I said at the beginning of this thread.

[Penguin]

Originally Posted by Fraser

That's exactly what I said at the beginning of this thread.

Then I guess we agree


P.S. FWIW, I know nothing of the EEC tests, but in the first 1,300 miles in my X5 35d, I've gotten between 26-28 MPG with mostly secondary highway driving. So I'm actually getting about what the US EPA ratings indicate.

[Fraser]

Originally Posted by Penguin

FWIW, I know nothing of the EEC tests, but in the first 1,300 miles in my X5 35d, I've gotten between 26-28 MPG with mostly secondary highway driving. So I'm actually getting about what the US EPA ratings indicate.

The EPA ratings do seem to be a better refection of real-world consumption than the more optimistic EEC ratings. I believe that both tests use the same basic methodology but differ in detail.

[AzNMpower32]

Originally Posted by Fraser

The EPA ratings do seem to be a better refection of real-world consumption than the more optimistic EEC ratings. I believe that both tests use the same basic methodology but differ in detail.

Oh trust me, carmakers find ways to get around the EPA tests as well. Like installing ultra-tall, useless 5th or 6th gears to make revs as low as possible. So sure, it might be efficient for a 4-cyl sedan to operate 100km/h @ 1600rpm, but in the real world, no one will be able to accelerate or maintain speed at those kinds of revs. But a lot of carmakers do that........*coughGMToyotaHondaFordcough*.

As they always say, it depends on driving habits and road conditions. I consistently achieve closer to the EEC numbers (well, okay the extra-urban are out of reach), with my highway averages being about 10-15% above the combined cycle.

[Fraser]

Originally Posted by AzNMpower32

Oh trust me, carmakers find ways to get around the EPA tests as well.

The EPA ratings still seem closer to real world results than that those created by the ECE R101 test as used in Europe and many other countries