Any fuel consumption figures you get or recommendations are only going to provide you will a very rough and general guide.
The fuel consumption on a Z4, and any other car, I’d going to be dictated by how YOU drive it.
I’ve had a 23i, a 35iS and now an M40i
The 23i was great on a run taking it very easy but when I went up my local twisties and gave it plenty the mpg dropped down mid teens, average low 20’s because you had to rev it a lot more to get the best out of it in a fun sense.
The 35iS on the motorway with cruise on was very frugal and returned nearly 40 mpg on the 500 mile trip home. When I got it home the average was 25/26 mpg and if you were out for a fun day would could drop to low teens (which Will (Tiglon) the new owner is attesting too) but that was rare to be that low, mid 20’s was the norm.
The M40i is the most economic out the lot so far, as it’s not run in yet and hasn’t been getting much spirited driving. It’s returning an average of 34.5 mpg. This will most definitely change when it’s got a few more miles under its belt :driving: but I do feel in normal driving with the 8 speed box it can be pretty frugal if it wants to be, and the driver will let it be.
As said the 23i and 30i are very similar and if you can stretch to the 30i go for it.
I have no experience on the 4 cylinder turbo engine but as usual with anything with a turbo, the more you spin it up, the more fuel it’ll burn.
Echoing other’s sentiments, I hope you do buy one as they’re great cars, stunning looking and don’t look anywhere as old or relatively cheap for what the are, but…………… if fuel consumption is one of your main considerations then it may not be the car for you. I think when you own a car like this you just accept that it will need filled up reasonably regularly and it’s just a cost of ownership
