Extended Service Intervals Affects on Catalytic Converters

Bulletin TB-80007
February 16, 2009

Gary Stamberger – Training Director
MagnaFlow Performance Exhaust

For some of us who have been around cars for almost a half a century, the thought of not changing your oil every 3000 miles is as foreign as today's TV Reality shows. I know that I personally adhere to the 3K mile oil change and stand by it as the best way to avoid costly repairs.

The advent of extended performance oils, synthetic or mineral based, together with the notion of low maintenance vehicles and a sagging economy has everyone looking at extending service intervals to the max.

So exactly how long should engine oil last and what are the repercussions if it is stretched beyond its limit? The new car salesman would like us to believe we can go three or four times longer between services while the service manager back in the shop cringes at the idea. Don't get me wrong… the lubricants that we have available today are far superior to those we had 30 or 40 years ago. The problem lies within the forces at work each and every time we start the engine. Things like extreme heat pressures, oxidation, environmental contaminants that are introduced through the air induction system and breakdowns in other systems such as cooling or PCV. These are factors we can plan for in the development of better lubricants, but in the end have no control over.

All of these stress factors can bring about damage in many ways to the engine but few of us give much thought to the lowly Catalytic Converter way downstream in the exhaust. The same problems that occur upstream can be carried downstream and collect in the converter. Carbon, fuel, oil, or coolant contamination, excessive heat and component failure like Oxygen sensors and spark plugs or wires. Physical damage from outside forces can crack and/or melt the ceramic substrate which can subsequently restrict flow to the point of causing a drivability problem.

Let's look at coolant contamination of the Catalytic Converter. A blown head gasket would be a perfect example. One of the causes of Head Gasket failure could be lack of maintenance and to complicate matters further, any coolant that may have gotten into the exhaust stream could eventually contaminate the Converter and or Oxygen Sensor to the point of failure. The problem here is that these component failures may not occur for weeks or months. It's the Snowball effect!!

Although usually overlooked, many drivability problems can be sourced back to lack of maintenance. Most repair technicians can point out specific instances where regular maintenance could have prevented a component or system break down.

I know that extended service plans are not the cause of all repair issues we face today, but I do believe they create a mindset that prolongs maintenance intervals long beyond what the manufacturer had intended.

Cleaning up the environment…one converter at a time