G20 Differential Fluid Change

IA EURO illustration of the BMW G20 rear differential seen from under the car, fill plug circled in red marker: oil comes out and goes in here, new plug, 60 Nm

That circled plug is the whole job on the back of a G20. BMW calls the diff oil lifetime fill. We changed ours anyway, and this is how BMW says to do it.

Find your car

The oil changes with the build month, not the model year. It's on the sticker in the driver's door jamb.

330i, rear-wheel driveRear only: G3 to 02/2020, G5 from 03/2020. 0.8 L.Kit $78.99 →
330i xDrive, built to 02/2020Front G2, 450 or 600 ml. Rear G3, 0.8 L.Kit $134.99 →
xDrive, built from 03/2020Front and rear both G5. No M Sport diff.Kit $165.99 →
M340i xDrive, M Sport diff, to 02/2020Front G2, 450 ml. Rear G4 only, 1.0 L.Kit $209.99 →
M Sport diff, built from 03/2020Front G5. Rear G4 only, 1.0 L.Send us your VIN

M Sport diff means option code S2T4A. Not sure what you have? Send us your 17-digit VIN and we'll tell you.

60 NmEvery diff plug on the car. M22, new plug with a new O-ring, every single time.

Rear diff

  1. Warm it up. Short drive, then park and lift the car level.
  2. Crack the fill plug first. If it won't break loose, stop here. An empty diff you can't refill is a tow.
  3. Suck it out. There's no drain plug. Run a suction hose down the fill hole and pull out all the old oil.
  4. Prime the pump hose with new oil so no air goes in.
  5. Fill until it weeps. Stop when a little oil runs back out of the hole: 0.8 L standard, 1.0 L M Sport.
  6. New plug, 60 Nm.

Front diff (xDrive)

  1. Panel off. Centre underbody panel: 21 screws, slide it out toward the rear.
  2. Crack the fill plug first, same reason as the rear.
  3. Find the drain. Some front diffs have a drain plug in front of the front driveshaft (14 mm): drain it there. No drain plug? Suck it out through the fill hole like the rear (our shop call, BMW only lists a level check for that version).
  4. New drain plug, 60 Nm. Wipe the old oil off the subframe so a leak shows later.
  5. Fill to the bottom of the hole: 450 ml or 600 ml depending on the diff.
  6. New fill plug, 60 Nm. Panel back on, 3 Nm.
IA EURO illustration of the BMW G20 xDrive front differential fill and level plug circled in red marker: fill to the bottom of the hole, new plug, 60 Nm
The xDrive front diff. The fill plug sits on the side of the housing, next to the driveshaft.
The wrong oil kills the diff. Front and rear take different oils, and the M Sport diff takes G4 and nothing else. Shake every bottle before you pour.

Where people mess it up

  • Car not level. Front up on ramps and you'll underfill the rear every time.
  • Air in the hose. The bottle says 0.8 L went in. It didn't.
  • Old plug back in. The O-ring is one-time. It weeps, and you find it on the garage floor.

Oils, amounts and torque values come from BMW's repair instructions and service information for the G20 3 Series. Check yours by VIN.

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