Oil changes are generally recommended once every 3,000 miles or every six months as a safeguard against operational fatigue resulting from frequent car trips that last less than ten miles, especially in cold weather; stop-and-go traffic, dusty conditions, and driving at sustained highway speeds during hot weather. Oil changes are especially handy in that they keep your engine from overheating or locking up.
A new engine with little or no wear will withstand having its oil changed once a year or every 7,500 miles. But the accumulation of miles on an engine results in increased blow-by, which causes more unburned fuel to be dumped into the crankcase, which causes the oil to degrade. Over time, this can bring about rapid and undue engine wear and all the problems that come with it, such as loss of performance and fuel economy, and increased emissions and oil consumption.
It is also necessary to replace the oil filter each time you change the oil, especially these days, as most oil filters on the market have been downsized from one-quart-capacity to one-pint-capacity to save weight, cost and space. The capacity reduction increases the risk of the filter becoming jammed with dirt, metal shavings and other debris before the next oil change.
There are many easy ways of knowing that your car is in need of an oil change. Fresh, new oil should be honey-colored and somewhat translucent. The older oil is, the blacker it gets. Also, low oil levels offer a strong indication, as the debris that collects in your oil filter is coated with the stuff. If the dipstick reveals that your oil is below the designated line, that means that the amount short has ended up in your filter with all the other junk, causing your engine to run lean.
If the oil needs to be replaced, a car’s “CHECK ENGINE” light will come on. In addition, many newer models will have a light that will indicate low levels or dirty fluid. In such an event, the matter should be investigated as soon as possible. When the light comes on, that means that your oil is in pretty bad shape already.
Finally, if your engine is making unusual noises, that could indicate that the oil level is low or that it is dirty, as oil dampens noise and reduces friction. One likely cause of pinging is the accumulation of metal shavings worn off from engine components. In that case, it certainly would suggest that your oil is due for a change.
Now that you are aware of the warning signs that your car needs its oil changed, you have the power to avoid some very serious problems. However, the best thing you can do to keep your engine smoothly for as long as possible is to change your oil and filter every 3,000 miles.