How Long Does It Take For Engine Oil To Go Bad When Your Car Isn't Driven?

Oil is the lifeblood of any internal combustion engine. It needs to be changed on a regular schedule, but oftentimes, drivers only consider the miles between oil changes. Does this mean if you only drive your car 1,000 miles per year and oil changes are recommended every 5,000 miles, you can use the same oil for five years? Not exactly. Oil has a limited lifespan and should generally be changed every six to 12 months, even if you're not driving your car.

You see, even if your car spends most of its time parked in a garage, the engine oil can degrade. Over time, it may begin to oxidize, and small amounts of moisture and dust could enter the oil system, slowly degrading it. So even that 1988 HSV Commodore SS Walkinshaw stored in a garage since new still needs its oil changed before driving it, even though the oil only has 12 miles on it.

How you drive your vehicle may also impact how the oil behaves over time. Even where and how you store your car can have an effect on the oil's life. For example, cars stored outside have to deal with fluctuating temperatures, which can accelerate the degradation compared to a car that's stored inside. If those rare drives you do take are short, it's possible the oil hasn't heated up enough to eliminate any moisture that may have found its way in.

It's not just reduced lubrication properties that can impact an oil's effectiveness if it's left to sit for too long. As moisture builds up in the oil when a car is parked for an extended period, it can trigger some corrosion in vital engine components. A little corrosion from driving on salty roads on the underside of your car probably isn't a big deal. However, corrosion inside the engine can be, and unless you're an expert engine builder, you probably won't be able to open up your engine to clean it. Fuel efficiency is also likely to be adversely affected by aging oil.

To prevent your old oil from looking like it hasn't been changed for 37,000 miles, consider the time between oil changes, not just the mileage. Changing engine oil every six to 12 months is a good idea, including the weekender you drive just a couple of times per month. Synthetic oil is more resilient than conventional oil and will last longer, but even so, regular changes are recommended.

There are a few easy ways to tell whether your vehicle is in dire need of an oil change. Check the color of the oil on the dipstick. If it has turned dark and no longer looks like the liquid honey it did when it was new, changing the oil is a smart move. Any signs of contamination, debris, or sludge are also a good indication that it's time to head to your local parts store to buy some fresh oil.