I was researching info about the e39/e53 (X5) low instrument cluster...and ran across the info below that went into greater detail about SIA III (service indicator display III).

Before today, I was still INCORRECTLY assuming that the same values used in SIA I and SIA II (fuel, mileage, engine temp, RPM) were still being used to determine "load".

The old SIA I formula was <b>e=a(1+t+r)</b> where:
  • e = estimated mileage
  • a = actual mileage
  • t = 1 (if engine operating temps is below normal) otherwise t=0
  • r = .5 (if engine is above 4500 RPM) otherwise r=0


So under this old calculaton, if you drove 5 miles with a cold engine @ 5000 RPM...the SIA I would calculate "e" as 12.5 miles although you only drove 5 miles:
  • a = 5 (the actual miles driven)
  • t = 1 (since the engine was cold and never reached normal operating temps)
  • r = .5 (engine exceeded 4500 RPM)
  • e = 5(1+1+.5)= 12.5 estimated miles


But starting with the 1996 model year...BMW started implementing SIA III where fuel is the ONLY value used to calculate "load"...see the info below for more details: