Thinking of buying an E83 BMW X3

I am considering buying an early 2004-6 BMW X3, due to ULEZ it needs to be petrol and we need an automatic too..

I've read various articles / forums on them but I'm trying to get a feel for how bad they really are on fuel, on Autotrader it talks of 16mpg around town which is where the car will spend a lot of time and it doesn't sound much better when on A roads. Am I kidding myself to think that the 2.5L or the 3L will return 25mpg on mixed driving?

My primary choice would have been an E46 325i Touring but for some reason, the insurance is 50% more than a 3 litre X3...

Any thoughts / experience appreciated.

Many thanks, I'd never thought of an Infiniti but I'll take a look around - could be a winner.

Cheers