How Often To Change Differential Oil In Rarely Driven Car?

A reader asks: I have a 2006 Honda S2000 that is driven just 1000 miles per year. The few miles that it does see are very easy miles. I last changed the rear differential gear oil about 4 years and 5000 miles ago. The car is stored in a warm garage and the diff has never been exposed to moisture. The gear oil used was AMSOIL Severe Gear 75W-90. How often should I change this gear oil when the car sees so few miles?

Our answer: Many car enthusiasts own have vehicles that they affectionately refer to as a “garage queen”. While these cars may see very few miles, maintenance still has to be a consideration.

When it comes to gear oil service intervals in sparsely driven cars, there isn’t much consensus. As differential oil that isn’t exposed to moisture, extreme heat or heavy loads has a very easy life.

That being said, everything oxidizes over time and eventually the additive package of the gear oil will undergo “fallout”. A very conservative service interval would be every 5 to 7 years. We are confident that a robust product like Severe Gear would last much longer. But this is likely a good window to freshen up the gear oil. This will keep corrosion at bay, wear control at its best and seals supple.

Other Stored Car Maintenance Notes

Regular maintenance is still required for cars that are rarely driven. Here are some notes on the subject.

• Fuel degradation is a massive concern and should be considered at all times. Make sure to add gasoline stabilizer when filling the tank. Degraded fuel can foul carburetors or injectors and fuel lines. Bad gasoline can also cause depositing and significant engine performance issues.
• Still on fuel issues, it’s a good idea to add carburetor or injector cleaner to the gas tank at least once per year.
• Change the engine oil at least once per year. This is the case regardless of how few miles the car travels over a year. Combustion by-products allow for acid formation in the oil over time. Older vehicles also have a higher tendency toward fuel dilution in the oil. Changing the motor oil just before long-term storage is the best course of action.
• Brake fluid tends to draw moisture out of the air, even though it is a sealed system. Brake fluid should be changed slightly more often than rear differential gear oil (every 4-5 years or so). Fresh brake fluid prevents the creation of rust and corrosion in the braking system.