You are already inquiring these kinds of things although you plan to replace your E65 in three years time?
Well, thats what i call "proper prior planning"... little bit far in advance though, isn't it?
Anyway, i'll try to answer some of your questions to my best knowledge.
I have a similar vehicle history, switching over from a E38 740d (which had basically the same engine as your E65) to (in the meantime it have been several) 535d, the last one being an F10 535d, which has the same drivetrain as the 740d and 640d you are interested in, in the case of the latter it's the same technical base, constructionwise.
First of all: don't let yourself discourage by the attempts at discrediting certain Diesel engines. The same was the case, when the 535d came out ("to much power from too little displacement") and over time it has not proven to be true.
Same goes for those people whose instant reaction is: "better buy a petrol engine", who can't quite comprehend the comfort an extended range without refueling offers.
What you probably already know is that any engine of comparable class but with only 6 cylinders will almost all of the time have better mileage than the respective 8-cylinder engine.
So, you can expect any of the cars you are interested in to have less fuel comsumption than your current one. Also, of course, because the drivetrain in toal (mostly the 8-gear transmission) is better by a magnitude than your current one and much more efficient.
You said that you operate your 740d at ~8,5l, which is quite on the lower end of the scale. You seem to be driving pretty economically.
Taking that into account you can expect to get below the 8l-mark with the 750d and with the 740d you might even see a below-7 value, at least on a regular basis.
In total, all of the 3l-inline-sixes don't differ that much in mileage, some people even say, the 740d can be driven more fuel-saving that the 730d because it hardly ever needs to use it's total output potential.
The 750d pulls ahead a little in the amount of fuel it uses, because of the all-wheel-drive and it's generally more performance-oriented layout.
If you want to have an impression of the comsumption of these cars under real-life conditions in germany (which for these cars is typically characterized very much by non-speedlimit-Autobahn drives), you should have a look at:
Spritverbrauch berechnen und Autokosten verwalten - Spritmonitor.de, that gives you a very good picture of the upper and lower ends of the scale at least.
My personal piece of advice is: take the 740d , it offers almost the power the 750d has, with less consumption. It can easily be brought to 360hp without decreasing the durability of the drivetrain and without hampering its basic frugality regarding the fuel. It then has in effect the same performance as the 750d.
It doesn't have the mandatory 4x4, which means that most of them have active steering, which gives the car a much better manoeuvrability and the BMW-typical sporty touch.
One last thing: with the ever-shrinking fuel tanks you will not neccesarily always have the 1000km of range, unfortunately. Even less so if you decide on behalf of the 640d, for which all the things i said go as well. Which one you prefer is purely a matter of personal taste. The technology is exactly the same.
PS: "Ze english" of some of our members is borderline hilarious. No offense
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FL 740d und 750d Verbrauch
Didn't really notice much of the turbo lag.
....
Linear-Darstellung
