One Day in the Life of a Dirt Particle

by Ed Newman
Marketing & Advertising Manager, AMSOIL INC.

When it comes to motor oil and engine maintenance, filters play a significant role. There are all kinds of filters on a passenger car these days, including the fuel filter, air filter, transmission filter, breather element filter and oil filter. Wouldn't it be great if one could write about filters from the unique perspective inside the filter itself?

As luck would have it, while preparing this column I had a rare opportunity to interview a talking dirt particle by the name of Dirtamus Silicapoulis. Not often is one afforded a first person account regarding what actually happens inside an engine. I share with you here portions of our discussion. Mr. Silicapoulis, or "Tiny" (as he prefers to be called), asked that I not reveal his address or phone because of the damage he has done and he doesn't want his past to come back to haunt him.

How much experience have you had destroying car engines? Well, personally, I have only been involved with vandalizing one car engine. But I come from a very large family, and my kin have been destroying engines for decades.

What do dirt particles do on a typical day? Mostly you'll just find us hanging out, suspended in air somewhere. Dirt particles are generally a fairly passive lot. We go with the flow, as they say. Wherever the wind blows that's where you'll find us. Believe it or not, there's over 400 tons of dust and grit hovering in a cubic mile of air in a typical city. We're talking, for the most part, about things you really can't see with the naked eye. We're not talking nuts and bolts, birds and small children. You can't see us, but wherever there's air, we're there.

Can you tell us about the day you ended up inside an engine? Tell us, Tiny, how did it happen? It was your typical hot summer day. I was minding my own biz, basking in the sun, floating along when suddenly, whoosh, I was swept by an air current into an intake manifold. Swallowed alive! Did you know that engines suck in as much as 1200 cubic feet of air to properly burn one gallon of fuel? The internal combustion engine is really nothing more than a big air pump. It inhales a tremendous amount of air.

I didn't know that. But how did you get past the air filter? Air filters have a challenging job because they must balance two functions that are at odds with each other. Their first function is to stop dirt particles like me. Their second is to allow airflow into the combustion chamber. If they stop too much dirt, they can inadvertently restrict airflow. If they allow unrestricted airflow, they'll be guilty of allowing too much dirt to pass. You can see the problem.

Are you saying air filters don't work? Not at all. They do a fairly good job for most airborne debris, but they have their limitations. Remember, they don't call me Tiny for nothing. Most air filters have a paper media, though there are also cotton gauze and foam filters. I've heard there's an oiled foam filter that works sort of like flypaper. Fortunately, my encounter was with a more porous paper filter and, being small as I am, I slipped on through.

How big are you? You mean how small? When I last measured myself I was somewhere around fifteen microns. About a sixth the width of a human hair. (ed note: human hair has a width of 100 microns.)

So what happened next? Gasoline that is squirted into the combustion chamber mixes with the air and airborne particles, including sand, salt and other minerals, which is then compressed by the piston and ignited. Boom! That ignition blast sets off a real shockwave effect. Most of the leftover air and debris gets swept out through the exhaust port. But my experience was different.

Somehow I got wedged between the piston and the cylinder wall. I later learned that most dirt particles in this engine came in that way, though some enter through vents.

Next thing I know, I begin grinding down alongside the piston, scratching, gouging, clawing as I am drawn down, down, down into the dark heart of the beast. Had I been smaller, I could have slipped right past, even though these are very small clearances. Had I been larger I would have been captured by the air filter. As it was, it was highly traumatic for both myself and that cylinder wall, piston and rings.

Do all dirt particles that pass the filter work their way into the engine like you? The dirt particles that enter into the combustion chamber, the majority of them pass right through to the exhaust port and out the exhaust pipe. It's a thrill for the dirt particle, but no big deal for the engine.

Those like me that come into contact with the moving parts within the chamber can get wedged between the piston and the cylinder walls. And in that area, the presence of the dirt will result in wear, both on the piston rings and the cylinder wall itself. Down a little farther, we cause wear on the piston itself. Eventually, as we move further down we're released into the crankcase area of the engine, where the oil reservoir is. We will mix with the oil, and the oil will pick up this contaminant, this abrasive material, and circulate it throughout the engine.

Who else did you see inside that engine? You might be surprised at the gang of vandals I found in that engine. First, there's the leftover debris from when the engine was made: casting materials, machining swarf, polishing compounds, even lint. It's a hostile crowd and it brings out the worst in a dirt particle like me. Then there's all those wear metals, the rebel non-conformists who followed me as I was clawing my way down along that cylinder wall. Some of the metal in that cylinder wall was scratched free. Dirt particles like me bring out the worst in an engine. Finally, there are exhaust gases, soot, acids and moisture. These can enter the engine via combustion blowby and cause corrosion or lubricant breakdown.

Before the interview you mentioned an interesting experience you had inside the oil filter. Can you elaborate? Oil filters can be dangerous for dirt particles because, well, you know, once you're trapped inside an oil filter it's all over. Fortunately for me, oil filters are not very effective for particles smaller than 20 microns.

This was my first time inside an engine. I'd heard some real horror stories about oil filters and was quite frightened as I began circulating through the engine. Suddenly I found myself in the canister. Here and there I could see clusters of particles all scattered about. They seemed to be shouting something as I rushed by but I couldn't hear what they were saying over the roar of the engine. Next thing I was squeezed through the filter media, past the anti-drainback valve and it was too late. My 15 micron size allowed me to pass on through the media and continue on my journey.

A little later, as I was carried through the camshaft region I asked another silica particle what to make of it. He didn't know either, but he said we'd be passing through the bearings and on to the filter again before long and we could try to circulate a little closer next time.

Sure enough, before long we were back inside the filter canister where I discovered they were iron and other metallic particles and they were not having a party. They were shouting for help. They had been captured!

Are you saying that oil filters don't do much good against dirt either? Not at all. Oil filters do, however, have their limitations. Again, it is the old trade off between restricting too much, and allowing too much unrestricted oil flow. Of course, there are by-pass filters that effectively eliminate particles smaller than me. That, my friend, is a subject I don't want to get into.

CONCLUSIONS? Simply this: Auto experts agree that dirt is the number one cause of engine wear. Oil filters and air filters play a critical role in preserving engine life. For lube shops they are a logical source of add-on sales, always in the customer's best interest.

NOTE: I'd like to give special thanks for to Dave Anderson, Technical Director, and Byron Selbrede, Technical Services Manager, AMSOIL INC. for their assistance in developing this piece.

This article originally appeared in National Oil and Lube News, August 1999