Solomon pegged the size of this consumer market, excluding commercial and public-sector fleets, at 678 million gallons in 2005. Do-it-yourself (DIY) oil change volumes represented only 28 percent of this, while the do-it-for-me portion – quick lubes, auto dealerships, garages and other repair facilities, plus about 10 million gallons of factory-fill oil – added up to 72 percent.

By 2010, the total market will grow to 690 million gallons, and by 2015 it will top 752 million gallons. The DIY share will keep shrinking, however, slipping below 24 percent in 2010 and to just 22 percent in 2015.

And this market isnt just declining in relative terms. Total DIY volumes peaked at 220 million gallons in 2001, and will drop steadily to the end of this decade, when demand will level out around 167 million gallons a year, Solomon said.

Some intriguing factors went into Solomons model. Vehicle registrations are growing (up more than 4 percent in 2005 over 2004), not because production is up but because scrappage is down. The average number of vehicles per registered driver is climbing (to 1.14 vehicles per driver in 2004, up from 1.08 in 2000), meaning fewer annual miles driven per vehicle. Consumers on average can be expected to change a vehicles oil fewer than three times a year by 2009, down from an average of 3.54 oil changes per vehicle in 2002.

It wont be long, Solomon concluded, before the U.S. DIY market is limited to enthusiasts and those who cannot afford professional oil changes. Are you ready for 2010?