This info is from BMW old school maintenance document (by Mike Miller):
- Engine oil 20W-50 and filter (8000km, full synthetic 12000km)
- Transmission oil Dexron III and filter (24000km, synthetic ATF 48000km)
- Valve adjustment (24000km)
- Air filter (48000km)
- Fuel filter (48000km)
- Spark plugs BOSCH 8WDC (48000km)
- Differential oil 75W-90 (48000km)
- Brake fluid DOT 4 (one year)
- Engine coolant (two years)
- Engine drive belts OEM or BMW (48000km)
For winter change to different oil weight, 10W-40 should be good for below zero celsius degrees. More information on temperature ranges can be found on owner’s manual. Use whatever your favorite oil brand is, Valvoline does offer excellent products for both oil weights (VR1 Racing and Maxlife). On rebuilt engine after break-in you may try fully synthetic oil, like 5W-50 for year-round use.
Valve adjustment is done like any other M30 engine, clearance is 0.30mm on cold engine. Remove radiator fan to access to 36mm nut on crankshaft end for rotating engine. New valvetrain cover gasket is needed for finishing job. Rotate engine one cylinder at time to top piston position, cam lobes facing bottom down. Start with 1st cylinder on top dead center, align crankshaft pulley mark to housing and continue from there. While valvetrain cover removed, check two banjo bolts holding camshaft oil pipe. Bolts can be replaced with self-locking version from BMW.
Maintaining valve seats in condition on old BMW means adding lead substrate to each fuel up. Likely this is not needed for late 745i turbo, it comes down to manufacturing year of cylinder head. If head is manufactured on or after september 1984, substrates are not needed according to BMW technical bulletin. Heads from this point on use hardened valve seats and are fit for unleaded fuel. Manufacturing year of cylinder head is cast on intake side, check there if unsure. In general it is recommended to use high grade fuel for better knock resistance.
Until early eighties BMW cars were maintained by periodic schedule. Introduction of service light system changed this. Also 745i turbo was meant to be maintained by indicators on instrument cluster. This covered oil changes and inspections as detailed in owner’s manual. After time cars started having problematic lights due to leaking batteries, making system less useful. Bad batteries present also other problems in cluster, it is recommended to replace them always with fresh ones. For maintenance it may be easier just use periodic schedule as starting point.