It always makes me laugh when people say this, as if they expect someone to be always justifying the purchase of a higher-powered engine 100% of the time they're driving it. Just because someone doesn't want to be hooning it like a loon constantly doesn't mean they don't have the right to care about fuel economy when they're doing the more mundane things in life, such as commuting to work.
My commute to work is boring as hell and I drive nice and sedately, whilst keeping up with traffic and sticking to speed limits, keeping my MPG reasonable whilst listening to music and generally staying calm and comfortable. There's no need to drive erratically and hammer it into every roundabout and corner only to meet traffic up ahead faster. But it doesn't mean I need or want to go and buy a ****** diesel to do it in.
I would say that 3 Series offers very good performance and very good economy!
I think it would a compromise on both. It wont be very good at either. Which is exactly my point. I didn't for a second suggest you have to be hooning it everywhere either. But to get halfway respectable mpg's you would have to drive it very sedately. So why bother with a 330i?
The difference being that with larger engined, quicker cars you won't be able to achieve near 40mpg on a run, you must know this?
Plus those quicker cars that go about it via turbo/superchargers (in particular) usually come with potentially epic repair costs, the n52 doesn't have a lot that typically goes wrong. Its all about compromise and expectation.
I'm not suggesting its some sort of world beating engine. A 335i would be a far, far more exciting daily drive but you'd also absolutely want the BMW warranty with it.
To suggest its not a good engine /car combo is IMO, extremely harsh
I think 35 mpg on a run was pretty much the limit I saw in my 330i, not that I did that often, as mentioned above. But my S4 (4.2 V8) did 30 mpg on a run, so a 5 mpg loss there, and 2 mpg overall, was worth it. This is just an example of course, but I can't imagine other modern, (European) ~4L V8's being much different on the power / economy front.
Don't diesels have higher running and purchase costs to equivalent petrol engines? Not to mention other things like differences in sound, throttle response and gear ratios etc.
Higher running costs is laughable to be honest. No they don't. Initial purchase costs, when new, are nearly insignificant. In fact, depending on how you compare models, a new 520d is cheaper than a new 520i. So no extra purchase cost. A saving in fact.
If your diesel is bought second hand, then yes, you will likely pay a little more, but then it'll be worth a little more when your finished with it. All the while, saving money on fuel. Obviously new diesels aren't necessarily suited to everyone, if you never leave rush hour traffic for example.
The rest of what you said is personal preference. Personally, I prefer the drive of a modern diesel for my daily driving duties, hence why I have one.
But that isn't the point here anyway, as we weren't talking about diesels? I was talking about why, IMO, the 330i is a compromise too far.