Based on that experience, and on data and opinions from many experts since, its clear that most of the wear that actually occurs in engines is not due to a lack of additives Nor is it a function of using the wrong type of base stock or viscosity index improver, or a lack of special conditioners designed for older cars. Its also not caused by deficiencies in NOACK volatility, oxidation stability or low-temperature pumpability.

No, one of the most common causes of premature engine wear is what collectively can be called dirt.

Dirt is the black stuff mechanics sometimes point to under the valve cover or in the oil pan when they break

the bad news about worn cylinders, rings, valves, rockers and bearings, or tell you the engine needs to be rebuilt. Dirt includes airborne silica and other roadside material inhaled through the vehicles intake manifold.

Despite the presence of additives, these abrasive particles can lead to the creation of more dirt: iron, chromium, aluminum and other metallic particles scuffed off the internal components of the engine and churned up while in operation. Byproducts of combustion and oxidation also kick in their fair share of dirt, in the form of hard and soft carbon and other sooty particles. And when any of this dirt gets between two precision-machined, moving parts separated by only a thin film of oil, there is a good chance that wear will occur due to abrasion.

Thats the bad news and its a reality. The good news, however, is that engine builders have long been aware of the harmful effects of dirt. Thats why engine oil has detergent and dispersant additives – and why engines have air and oil filters. Air filters are designed to keep engines from inhaling dirt, and oil filters are designed to remove dirt that finds its way into the oil.

But whats the dirt on these filters? Are they doing their job? Are OEMs and oil companies as concerned about the quality of air and oil filters as they are about the quality of engine oil? Based on the lack of standards in the industry and the comparatively low level of communication that exists between the OEMs and aftermarket filter manufacturers, it appears not.

To start, take a look at the air filter, a vehicles first line of defense in keeping harmful dirt out of the engine and its oil. Whereas every vehicle owners manual will clearly state what type and grade of oil to use, it usually says little to nothing about the quality of the air filter. There is typically no mention of air filter specifications, efficiency minimums, seals of approval, letter designations, starburst, donuts, or other symbols to help identify the quality of air filter to be used. Instead, it simply says to change the air filter at some interval; in many cases, it recommends using the OEMs genuine part as a replacement (i.e. Motorcraft FA 1616). And for those persistent enough to try, go ahead: Call the dealer, the regional parts and service official, work your way up to Detroit. Odds are that you will find few, if any, willing to state the performance requirements for their vehicles air filters.

Since most OEMs are silent on this issue, any requirement beyond the filter fitting the vehicles air box is left up to the aftermarket and its customers to figure out. The only seeming guidance from OEMs is the ISO Standard 5011 (formerly SAE J726). But dont be fooled, this standard is not about minimum performance requirements, as with engine oil. Nor is it tied to a tripartite group comprised of automakers, filter manufacturers, and others working tirelessly and spending millions to assure optimal fuel efficiency, maximum engine life and maximum oil drain intervals. ISO 5011 simply defines a precise procedure used to test air filter efficiency. There is no obligation to use it or any other test to define air filter quality. As a result, what we have is a mixed and murky bag of automotive air filters in the marketplace.

Whereas some filter manufacturers boast efficiency ratings of 99.9 percent, others offer efficiencies of 93 percent. Who knows what the average efficiency rating is in the marketplace? Many filter manufacturers simply elect not to report an ISO 5011 efficiency rating at all, using marketing terms instead to describe their products. Their labels offer high efficiency, increased protection, micropores, synthetic fibers, superior filtration efficiency, better air flow and other empty assurances.

So whats the dirt on air filters? The dirt is that there are no standards and no minimum performance requirements readily available or visible in the marketplace. And if your air filter looks clean, the reason may be because dirt is getting past it. When that happens, wear may occur until the oil filter can get the dirt out.

Next month, a look at the dirt on oil filters.