26mpg from a 330i? From my pre LCI early 335i with the less efficient N54 engine my average over many thousands of miles, 90% of which were me driving enthusiastically on A roads, was 28mpg.
Driving a much more efficient engine, with less power at a normal pace on less fun roads should easily see mid 30s average.
Not to mention the 330d is much better than efficiency wise than a 335d engine. The average figures people say they get is around 35-37mpg on a 335d and 28-30mpg on a 335i, hence Fox's 8mpg margin is between the models is about right. Whether or not you choose to believe it is another issue entirely.
Well, my first point was comparing results from fuelly, as that can be corroborated. However, it is also true that I have actually owned all the engines we are talking about here, except the 335i, for which I have stated that fuel economy on that engine is almost irrelevant, as it was worth it. Anyway, again, from fuelly, over 1,000,000 tracked miles on a 335i puts it 26-28, which is a good 10 - 12 mpg less than the equivalent 335d, not that this is what was being compared.
When I had my 330i, I was in the region of 26-28 mpg averaged over around 10k (I think it was actually 27.3 IIRC, but still well within the range I mentioned). And I didn't find it fast enough for that fuel economy.
My 335d averaged 37.9 over 17k which is about what you are saying. Although we weren't really comparing the 335d here. But was easily fast enough for that fuel economy, as it was much faster than the 330i.
I haven't actually owned a 330d for any length of time, I do know a few people who have, and they are averaging around 40 mpg, maybe a little more, which tallies up well with my experience of the 530d, which is currently kicking around 39.1 but is only on 8k, so still breaking in, and my last 6 tanks have all been within around 0.5 of 40 mpg.
So based on my actual experience, I will choose not to believe that the difference is only around 8 mpg. On COMPARABLE 3.0L non turbo petrol / single turbo diesels (i.e. second from top for each fuel type, excluding M cars).
As for the selection bias Fox, I was picking the years that had the most cars available, at around the age I thought the OP's budget would allow. I.E. 2006 - 2008 (not that he actually mentioned a budget, but the whole pre-LCI comment and lack of i-drive would suggest he is looking at around that age of vehicle). So it wasn't for nothing. It was to compare real world figures, tracked over 1.5 million miles. Sure, they are different cars, and may well be bought for different purposes, but surely this will even out somewhat over such massive miles covered? Not everyone buys a petrol bmw for drifitng roundabouts, likewise not everybody buys a 330d for uber economy.
And surely there must be a reasonable difference in economy between e39 diesel engines and e90 diesel engines? With the later engines being a little more economical?
And at no point was I comparing "on a run" figures. I could see 50 mpg "on a run" in both my 335d and my 530d, if I wanted to. Just as I could see 35+ mpg in my 330i. But neither is representative of actual running costs. Who is always driving "on a run"?
![[TW]Fox](/data/man-of-honor/2009.png){kind=avatar}
