When Is the Best Time to Change Your Oil?

Driving in stop-and-go-traffic consumes large amounts of fuel and massively pollutes the atmosphere and oil as the engine accelerates and decelerates. Short trips never allow the engine to properly warm up and the computer never locks on – meaning the computer does not have the chance to take control of all functions.

Prior to locking on, the computer is in a preprogrammed mode designed to warm up the engine to operating temperature. In this mode, it does not meet emissions requirements or provide good gas mileage. It’s as if one is essentially driving with the choke on.

Prolonged idling subjects the engine oil to lower pressure and high heat. Urban freeway driving is beyond my experience. Honestly, there is not a stoplight within 48 miles of my house.

So, with these variations in driving conditions comes the inevitable question that auto enthusiasts have been asking for years: “When is the best time to change my oil?”

If you believe the quick oil-change establishments, you’ll change your oil every 3,000 miles or three months, whichever comes first. The driver’s manual in most vehicles typically shows a longer oil change interval. Who’s right?

I have always been blessed with a good sense of smell. Taste and smell are closely related, and as such, have enabled me to determine individual ingredients in my wife’s kitchen concoctions. I’ve put on several pounds while being asked “What else do I need to add?” Identifying ingredients is a tough job, but (luckily) I’ve got the equipment, and someone has to do it.

I am not about to propose that you determine when to change your oil by using your sense of smell, but it has its place. The pollutants that collect in oil can easily be measured by gas chromatography, a form of sniffing. This, along with other chemical and physical measurements, help read what is happening inside the machinery.

If it were not for the abundance of oil in this country during the last century, perhaps we would have developed the “on-board” equipment to determine when to change the oil. I have been impressed with the auto industry’s response to the demands of the new pollution requirements in the last 30 years. The industry has developed an impressive array of electronic sensors for our modern cars.

These inexpensive sensors measure water, air temperature and oxygen content (in an 800+ degree mixture of gases), camshaft and crankshaft rpm, engine knocks, and the position of various valves and switches that affect pollution output. It would be great to have a light come on, one that accurately indicates the oil needs changing. If we had this, we wouldn’t worry about severe or normal oil change cycles.

The oil change interval is one of the most popular topics of discussions on the MachineryLubrication.com message boards. Heated discussions always erupt between supporters of synthetic and mineral oils. Everyone has an opinion of how long you can leave your oil in the crankcase. Some amazing oil change interval claims are made.

With environmental problems created from the manufacture and disposal of motor oils, we should strive to use the lubricants for as long as we can. However, all lubricants, both synthetic and mineral oil-based, will become polluted and degrade with use and time.

One of my best friends is a school principal. Though the man has a doctorate in education, he would never understand discussions of an automotive or oil-related nature. I trust him in his area of expertise, and I feel he trusts me in mine.

His knowledge of automobiles is so limited that I must be careful when I recommend future service on his vehicles. His response is to do the maintenance now, not later. The two habits that I cannot convince him to change are his exclusive use of premium gas, and changing his oil every month. But I cannot argue with his success: He drives a 1979 Oldsmobile Cutlass with a V-6 and a 1991 Ford Crown Victoria with a V-8. Both cars are driven daily, and each has more than 200,000 miles. I have never had to make any internal repairs on either of these engines, and may never have to.

Take a hint from a principal who knows little about cars: take care of maintenance now, not later. Oil is still relatively inexpensive compared to mechanical repairs. To err on the side of caution is financially desirable.

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