There are a lot of variables that impact when to change your oil. Most shops recommend changing it every 3,000 miles, but new cars in optimal driving conditions can sometimes go as far as 5,000 miles, whereas older cars, cars that often tow heavy loads, or cars that often drive in extreme cold/heat might need to replace their oil as often as every 1,000 miles. Drivers also need to consider which kind of oil they use (synthetic oil is good for up to twice as long as conventional oil), how often they are caught in stop-and-go traffic, how many short trips they take around the city, and so on.
So, in addition to keeping track of your mileage and the date of your last oil change, regularly checking your vehicle’s oil level and quality can help a lot in determining when to replace your oil.
To check your oil level, find the oil dipstick in your vehicle (you can look up where it is in your manufacturer’s manual if you are uncertain). After your engine has been off for at least ten minutes, remove the dipstick from its tube and wipe it off with a clean, lint-free rag. Then insert the stick all the way back into the pipe, and pull it out again.
Note how high the oil film reaches on the dipstick (where it falls beneath “full” or “add”). If the residue doesn’t reach above the “add” line, then it is time for an oil change.
Also, check the quality of your oil. Though oil turns black pretty quickly, you should still be able to rub it between your fingers cleanly. If the oil leaves a dirty smudge or if it smells like gasoline, then you probably need to change it soon, as you are running contaminated oil through your vehicle.