Your vehicle owner’s manuals have schedules for preventive maintenance: things like oil changes, transmission service, and so on. They say you should change your oil after a certain distance traveled or after so many months. Most drivers understand this very well. What they may not know is that there are actually two service schedules: the regular schedule and the severe service schedule. The mileage and time intervals are lower on the severe service schedule.
Now when you hear ‘severe service,’ you may think it doesn’t apply to you because you don’t feel your driving conditions are severe or extreme – it’s just normal everyday driving. So let’s list some of the conditions that classify as severe so that you can make the judgment on your own driving.
Before we start the list, here’s a point of contrast that definitely is not severe driving. Driving down your nearest NM interstate at the highway speed limit on a 75 degree F/24 degree C day loaded only with your passengers. This is an easy trip for your vehicle: your engine is loafing along at low RPMs, no heavy loads to pull and moderate Albuquerque temperatures. Now let’s look at some severe service driving conditions.
Most trips around town are less than four miles/six and a half kilometers. When your vehicle engine cools down, moisture condenses in the engine. This water in the oil doesn’t get a chance to evaporate on short trips because the oil doesn’t get hot enough. A lot of short trips in your vehicle means a lot of water build-up. And water in the oil leads to the creation of sludge which can damage the engine. Changing the oil more frequently keeps sludge from building up. By contrast, highway driving warms the engine up and gets the water burned off.
Here’s another example. Most trips around Albuquerque are less than 10 miles/16 km and outside temperatures are below freezing. This is the same reasoning, but in very cold NM weather it takes even longer for the oil to get hot enough to evaporate the water, hence 10 miles/16 km as opposed to 4 miles/6.4 km.
Next, you drive in very hot NM weather. The hotter it is outside, the more cooling the engine, transmission, brake fluid, and so on becomes. The environment in which the fluids reside is more hostile, and the fluids simply break down faster. Therefore, the lower change interval.
Another: driving at low speed most of the time. Every vehicle engine has what’s called its powerband. This is a range of RPMs in which it’s most efficient. Low-speed driving doesn’t keep the engine in its power band so it’s working harder. This is one of the reasons that ratings are worse in downtown than on the highway.