Oh, those sludgy squdgy valves.

Shell says in its recent batch of television commercials, that the petroleum titan is adding nitrogen to its gasoline to clean gunk off of valves and other moving parts.

Those who understand how an automobile engine works should immediately recognize the colossal blunder in the ad.

Meanwhile, the atmosphere is already almost 80 percent nitrogen by volume, so there's already loads of the inert gas entering the cylinder. After the gasoline burns, the catalytic converter quickly breaks the nitrogen oxides created at high temperatures, into nitrogen gas and water.

So, what is it Shell is adding? Nitrogen is present in protein, and countless other compounds. But it is most often associated with explosives, (the nitro in nitroglycerin), ammonia, hydrazine rocket fuel, ammonium nitrate, and all sorts of nasty stuff. Of course, so is oxygen, carbon, and every other element, other than xenon, helium, and stuff like that.

Did you figure out the blockhead mistake in the ad yet? The ad shows gasoline showering down on a cylinder valve, cleaning away accumulated sludge. That would mean gasoline in the rocker panels and on the cam shafts. Gasoline never gets into cam shaft territory and certainly does not stream onto the tops of cylinder valves.

The only gasoline that hits the top of a valve would be a gas-air mixture, vapor really, from an ancient device called a carburetor, which cars don't use these days.

That makes the add doubly mysterious. Companies put all sorts of compounds into gasoline to maintain the engine, such as nitrogen-containing detergents, petroleum distillates, and who knows what else. But nitrogen?

And someone should have pointed out that if gasoline reaches the external tops of the valves, something is seriously wrong with the engine, like it's in the middle of a horrendous crash and is disintegrating.

To clean the tops of the valves, put some cleaning goop in the oil. Gasoline goes into the cylinders via the valves, and the valves are lubricated and cleaned, or not, by oil that circulates through the engine.

T0 clean the underside of the valves, where the high temperature gas-burning takes place, add something to the gasoline.

Don't expect that nitrogen-laced gasoline is going to make your engine last 500,000 miles.