Where are you located? Or more precisely, what range of temperatures do
you expect before your next oil change? I am in Texas in the US (hot
summers and mild winters), and in my E36 I put in 10W30 each fall and
15W-40 each spring. I've been using synthetic blend, and so far the car
has never used any oil between changes. I have about the same mileage
on mine as you do, but I have the 325i.

I've always thought it was better to use a narrower range of viscosity
if you don't expect wide variations in temperature, but with full
synthetic it is robably not so much of a concern as with regular oil.

David

what are your recommendations?

What do you think about using  Fuchs oil 5w50 (sythetic oil)?

My engine has about 140 000 km.