Oil requirements according to the BMW manual for a 1995 318ti.
Weight / Temp range (F)
20W50 / 20 to > 90 (Their chart stops at 90F with arrows pointing higher)
15W50 / 0 to > 90
15W40 / 0 to 90
10W40 / -20 to 60
10W30 / -20 to 40
5W30 / < -20 to 20
5w20 / < -20 to 15
So in my eyes the only 2 oils that meet the normal spec of my engine are 20W50 and 15W50. Unless I'm traveling in the winter to the colder parts then the 10W40 has me covered. In 95 they did not use synthetic in the TI, it was standard oil. I switched to synth when I bought the car. at 80K miles, its now at 180K...
Avoid the "Green cleen" oils, they are reduced Zink/sulfur formula and do NOT protect tappets or followers as well as standard oil (Wich as of this year in the US does not have much zinc either...
) Important in motors that have a more mechanical valve train and rev as high as ours.
All my humble opinion...
Dave