BMW 3 series 1991 1.8 petrol service and maintenance

Engine oil

Engine oil capacity: 4 litres (4.2 quarts)
Recommended oil type (Oil Viscosity Classification SAE) is 5W-30

Timing belt

Based on practical experience, recommended BMW 3 series 1.8 timing belt change interval is 40,000 km when belt should be replaced, or at least periodically check the belt's condition after this mileage and replace it at the first sign of damage.
Running your car in aggressive environments (e.g. salt, sand, etc.) causes timing belt to degrade faster and reduces its lifespan; under such conditions, the belt may need to be replaced sooner.