Scheduled Maintenance: Normal or Severe?

If you have ever looked at your manufacturers maintenance schedule you may have noticed there is a "normal" service schedule and there is a "severe" service schedule. Most people figure they fall under normal service and follow that schedule. If you ever read the definition for severe service though, you may find your vehicle use falls into that category.
A 2002 Chevy Silverado for example has an odd way of determining which schedule to use. "Follow the NORMAL schedule only if none of the conditions from the SEVERE schedule apply."  Italics are mine. (ONLY IF NONE). So, if ANY of the severe conditions apply to your vehicle use you should be using the severe schedule. Let's look at the "severe" conditions:

Follow the SEVERE schedule if any one of the following are true:
Most trips are less than 5 to 10 miles.
Most trips include extensive idling. (such as frequent driving in stop and go traffic)
The vehicle is operated in dusty areas frequently.
Trailer towing or using a carrier on top of the vehicle frequently.
The vehicle is used for delivery service, police, taxi or other commercial applications.

Remember, if any ONE condition is applicable to you then you are in the SEVERE condition schedule definitions. Interesting huh?  I'm not sure what the differences are on the schedules themselves. Spark plug replacement isn't a huge difference. In fact, it is a little odd. Normal suggested spark plug replacement, 100,000 miles. Severe 99,000. ?? Thats weird. I would expect oil change to be different. Lets see. Replace oil at 3,000 under severe or 10,000 under normal. Huge difference there. Good time to note, oil change is not the same as oil check. Check your oil level occasionally between changes and if it needs oil, add oil. But never try to top off oil if it is less than a quart low. Wait for it to be a quart low, add a quart.

Moving on.

2008 Ford Escape. The Ford severe duty is called special operating conditions. Towing a trailer, using a camper or car top carrier. Extensive idling, low speed, commercial use (taxi, police, delivery). Operating in dusty conditions. Off road operation. Use of E85 50% of the time or more (flex fuel engines). I was curious about the spark plug change schedule here because I had one with 112,000 miles that the plugs were original and severely worn. Normal oil change intervals are at 7,500 and plugs at 90,000. Severe schedule is oil changes at 5,000 and plugs at 60,000. Ford says if you are operating at any of the severe duty conditions only rarely then you can stay on the NORMAL schedule. Good to know.

Let's jump it up a bit to a less older car. 2011 GMC Acadia. This was in recently also with original spark plugs at 180,000. I would say they don't pay much attention to scheduled maintenance but let's take a look. The service definitions are the same as for the 2002 Silverado. Normal schedule has oil changes at 7,500 and spark plugs at 100,000. Severe is oil at 3,000 and plugs at 100,000. No difference then as far as plug change. Only 80,000 miles past recommended replacement. No wonder it was misfiring.

Well that was some fun huh? Something to think about anyway. Have a good weekend!

Kenny@ggauto.repair