Differential Oil Change

Differential oil change intervals

The owners and service manual recommends the following intervals:

Normal driving conditions: Every 48.000km / 30.000miles or 2 years (which ever comes first)
Harsh driving conditions: Every 24.000km / 15.000miles or 1 year (which ever comes first)

Definition of harsh driving conditions

The service manual states the following definition:

Less than 8km (5 miles) per trip on non-freezing weather conditions.
Less than 16km (10m miles) per trip on freezing temperatures.
In hot weather climates with temperatures above 32°C/90°F.
Extensive idling or long periods of stop-and-go driving (e.g. as taxi or commercial deliver vehicle).
Driving on mountainous roads.
On muddy, dusty, or de-iced roads.

Additionally definition from other S2000 owners:

Sport and fast paced driving with a lot of VTEC engagement.
Long periods of driving at 150km/h (93 mph) or above.
Racetrack driving (most people recommend to change the oil after each racetrack visit).

Recommended differential oil

See: Differential oil recommendations

Required tools and fluids

1L / 1qts differential oil (or a little more if you would like to "flush" the differential)
New crush washer for the oil drain bolt (Honda #90401-PCZ-003 / 18/x/Aluminium / See: Washer#Differential_oil_drain_bolt)
New crush washer for the oil filling bolt (Honda #90402-PCZ-003 / 18/x/Copper / See: Washer#Differential_oil_filling_bolt)
23mm socket or wrench (there is only limited space around the filling bolt; 23mm is not common so double check your inventory)
24mm socket
Ratchet
Torque wrench (44Nm / 33 lb-ft)
Oil catch pan
Floor jack + 4 jack stands
(Optional) A lube pump as it can be hard to fill the oil in the differential.

How to change the differential oil

Pre-conditions and jacking up the car

Before your start it might be a good idea to drive the car for a while to increase the temperature of the oil in the differential.
Put the car in the first gear and set the parking brake.
Jack up the car on the front by using the central jacking point near the engine.
There are two front-jacking-points on each side. Place one jack stand on each side at the jacking-point that is the furthest away from the front wheel.
Lower and remove your floor jack and continue jacking up the rear by using the jacking point on the differential.
Place your jack stands on the left and right side jacking points at the rear of the car.

Draining the oil

The differential is located at the back of the car / at the end of the driveshaft and has two bolts (drain and filling).
The bolt on the bottom of the differential is the drain bolt while the upper bolt on the drivers side is the filling bolt.
Place your oil catch pan below the differential drain bolt.
It is a good idea to first remove the filling bolt and afterwards the draining bolt. This ensures that the filling bolt is not stuck and prevents your from ending up with a drained differential that you can't re-fill.
First remove the differential oil filling bolt with a 23mm socket or wrench from the differential.
Next remove the differential oil drain bolt with a 24mm socket from the differential.
The old differential oil will now drain from the differential and you might need to re-adjust your oil catch pan.
You will notice that once the filling bolt is gone, more oil will come out of the differential oil drain.

Once all the oil has be drained I like to fill fresh oil into the differential to "rinse or flush" the differential with the new oil.
Wait until no oil (either old or new from "rinsing") comes out of the differential.

Adding new differential oil

Replace the old crush washer from the differential oil drain bolt. The drain bolt is magnetic so clean it and remove any metal parts.
Usually the crush washer will have two sides, one that has a rounded edge and one that has a sharper edge. The sharp edge should face the differential.
Hand tighten the differential oil drain bolt. Then use your 24mm socket and a torque wrench and tighten it to 44Nm / 33 lb-ft.
Fill in the new differential oil through the filling hole until the differential oil starts to leak out of the filling hole.
This is the indicator that there is enough oil in the differential (usually 0,8L / 0,8qts).
Replace the old crush washer from the differential oil filling bolt.
Usually the crush washer will have to sides, one that has a rounded edge and one that has a sharper edge. The sharp edge should face the differential.
Hand tighten the differential oil filling bolt. Then use your 23mm socket and a torque wrench and tighten it to 44Nm / 33 lb-ft.

How to make sure no old differential oil is left in the differential

This guarantees almost 100% that no old differential oil is left in your differential and that it has been exchanged completely with new oil.
The same procedure is used by oil companies between test cycles in their R&D facilities.
You might want to do this when changing to a different type or brand of oil.

Repeat the steps How to change the differential oil three times and drive your car for a short time between each changing cycle.