If you're unsure when your last oil change was, it's fairly simple to judge how far away from an oil change you are by checking the oil's clarity. Think of it like shampooing a carpet. As you clean the carpet, you can see the water change from clear to brown. After a while, the water is no longer clean and needs to be replaced. Although checking the oil's clarity isn't an exact science, inspecting it just might keep you from serious vehicle maintenance down the road.
Your engine's oil helps absorb heat from the engine and lubricates moving metal parts that would otherwise grind together. As you drive, the oil pump circulates oil within your engine and the oil filter catches the deposits that build up over time. The oil filter performs its own type of car maintenance by keeping the oil clean. But as the oil gets older, the number of deposits in the oil continues to build and the filter is unable to extract all of the material. When this happens, the color of the oil changes and it indicates the oil should be changed.
To check the clarity of the oil, let the car run for a few minutes and then shut it off. Find your oil dipstick, pull it out and check the level of oil and its color. If the oil is a dark-brown or black color, like Coca-Cola, then your oil needs to be changed. However, if it appears to be lighter, like the color of a cup of tea, then you still have some time before it needs to be changed. Changing your oil is a quick and easy auto maintenance fix, so don't be intimidated.
If you determine by your engine's oil clarity that it needs to be changed, it's best to not waste any time doing so. Waiting too long to perform this basic automotive maintenance can have serious implications for your engine.