Dear Tom and Ray:

While I was attending the University of Oklahoma in 1960, a study was done by the petroleum engineering department. The question was: Is draining oil from a vehicle necessary? They worked with White Trucking Company and tested their theory on long-haul trucks. Using only a "toilet paper" filter and only adding oil, they ran one set of trucks against ones that received oil and filter changes for 100,000 miles. The results showed no significant wear differences between the two. They also concluded that the oil in the no-change vehicle was "stronger," because the weak molecules in the oil broke down and evaporated away. This study was going on at about the time that the Conoco Oil company was working on biofuel and had developed a plant in Bartlesville, Okla. But then both the study and the plant were suddenly gone, and I never heard any more. What is your take on the oil-change theory? -- Don

TOM: Ah, yes. I remember that study, Don. It was funded by Charmin.

RAY: Actually, while we don't know anything about that particular study, I'd take it with a grain of salt.

TOM: First of all, motor oil has improved dramatically in the past 50 years. So whatever was done then probably doesn't apply now.

RAY: Also, long-haul, diesel trucking engines are built to last much longer than automobile engines. So 100,000 miles might not have been enough to show the damage of forgoing oil changes.

TOM: We have heard about the toilet-paper filter, though. It's called a Frantz Filter, and it has had a small cult following throughout the years. As you might expect, you install the housing, and then you simply stick a roll of 1,000-sheet, two-ply, 100-grit toilet paper in the holder, and that does the filtering. When it's dirty, you remove it and insert another roll.

RAY: It's not a surprise to us that it never caught on in big numbers, because it requires men to change a roll of toilet paper.

TOM: Aside from that fatal flaw, we've had good reports about it from our customers during the years. But keep in mind that anyone who would go through the trouble of installing and using one of these things obviously is very interested in car care and maintenance. That kind of person probably tends to take particularly good care of his car in all kinds of other ways, which could skew the results.

RAY: In any case, Don, our personal experience at the garage suggests that changing the oil and filter regularly is good, and not changing the oil and filter regularly can be very bad -- even catastrophic over the long haul.

TOM: And it's relatively cheap insurance. It's twenty or thirty dollars a few times a year, for most people. So we still strongly believe in changing the oil in your car, and changing the toilet-paper roll in the bathroom. And not vice versa.