I wouldn't be surprised if the 35i is slightly cleaner than the 35d, as the 35i is new technology and the relevant 35d drivetrain debuted back in 2006 in the 535d (the M57 itself came out in 1998, the one sold in the X5 debuted in 9/06).

For comparison purposes, the xDrive40d is cleaner than the xDrive35i with lower fuel consumption and CO² emissions.

OK, since you asked. ;) I think early hybrids were not particularly green on a life cycle analysis. However, the new NiMH batteries are a lot better than Nicads. They come with a 100,000 mile/8 year warranty, and the failures during the warranty period are reported to be very low by Honda and Toyota. When they fail (normally by wearing out), they usually only have 80% capacity, they don't actually short out. There are much cheaper battery replacements available now if they do need replacement. And Toyota has now launched their battery-to-battery recyling program whereby old NiMH batteries are turned into new NiMH batteries.

Toyota launches NiMH battery-to-battery recycling program — Autoblog Green

As a result of the above, I think the hybrids are a lot greener than they used to be.

We could talk about the environmental harm of mining the metals for the batteries, but then we would also have to consider the environmental harm of crude oil production, which is the usual alternative.

With respect to the greenness of any SUV, you have a point. The problem is that people often see it in extremes, comparing their current large SUV to a Smart car, realizing that it isn't a suitable replacement, and then carrying on with the SUV lifestyle. However, trading an E53 X5 gasoline model for a new generation X3 with a four cylinder diesel (in the same size vehicle), combined with reducing unnecessary trips, could result in a significant reduction of both fuel burned and emissions produced, two green measures. Selling our 2003 X5 3.0 and going to a 2007 X3 3.0si (gaining 40 hp and the resultant performance) resulted in a 25%-30% fuel saving in my case, for the same distance travelled. I expect our next vehicle changeover to do that again. So let's say I get a 50% reduction in fuel consumed, over several years, for the same driving distance (we are actually driving less, by choice). Nationally, what would it mean if we could reduce oil dependency relating to personal transportation by those sorts of numbers?

I need to disagree on both of your points:

Better mileage with the 35d and better/lower CO2 output so greener in that sense. How does the newer tech tranny make it greener?

With 425ftlbs of torque (v. 300ftlbs for the 35i) and reviews of the newer 8 spd tranny 'hunting' for the right gear, I don't miss the new technology or lower mpg/higher CO2 in the 35i either. The six speed with all that torque is perfect. 40d will have the 8 spd to make manufacturor easier/efficent.

I can understand your focus on fuel efficiency at the pump vs barrels of crude, since you pay at the pump. It isn't the measure that was used to start this thread, but that's fine.

What I don't get is why you focus on CO2 output and don't consider NOx output when comparing gasoline models to diesel models. There are lots of published CO2 figures since that is the primary regulated emission in Europe. However, in North America, the effects of NOx are considered and regulated to such an extent that they are the reason you have a urea injection system onboard your 35d.

I understand your points and appreciate them. However, I was purely responding to the post presuming that the 35d was less green due to the lack of an 8 spd tranny/'old technology'. I know/knew that the 35d has better mpg and co2 numbers and used that in my response. Can also add better NOx numbers to my response.

Fair enough.

I think that AzNM was correlating year of introduction to 'greenness' and that failed IMO due to the inclusion of diesels and gasoline models in the same list. He compared the 35d and 35i.

The comparison of the 40d is very difficult since it isn't compliant with emissions regulations in this market. I think that the 8 spd transmission is incidental, and not causal.

Agreed. I doubt the 40d will be grand enough to upgrade into? Suspect a diesel hybrid may be necessary or perhaps a plug in "plus" like the volt or just announced BMW sporTs car electric+ engine in an x5.

I think you would have to move offshore to upgrade into a 40d. There is no business logic to making it compliant in North America at any point. Development dollars aren't being spent on compliance for the last generation of products. Now, the 45d tri-turbo would be a different story...

The xDrive35d emits 262 g/km versus 236g/km CO² for the xDrive35i. Naturally though, the diesel consumes less fuel.

That is suprisingly high for the 35d. The 30d is at 196 g/km, the 40d is at 198 g/km. The BMW.com site doesn't list the 35d. However, in the 3 series and the 5 series, the 35d has a 25% advantage over the 35i, and is almost identical to the 30d.

Edit: On the UK cycle, the X5 35d is reported by another source at 216 g/km, which seems believable given that it is a different test cycle.