For millions of drivers, that habit is entrenched. After buying engine oil through such outlets, they routinely slide under the car with a drip pan and a rag, a drain-plug wrench and oil filter wrench (or sometimes just a screwdriver and a hammer). They then change the oil themselves.

Some DIYers do this because they love their rides and enjoy a certain intimacy with their cars when changing oil. Others fancy themselves mechanics, or motorheads who know more than most about automotive lubrication. In addition, by doing it themselves they feel they can avoid the problems of an over- or under-filled reservoir, a loose or stripped drain plug, and other careless mistakes.

Then there are those who want to save money. Rather than spend $25 to $30 for someone else do the dirty work, DIYers know they can save roughly $15 to $20 if they change the oil themselves. In addition, they dont have to wait in line at an installer and endure a barrage of up-sell pitches while trapped in their car with the keys on the dash.

DIYers are a hardy group and some will likely still be around at the turn of the century – but they are a dying breed. From 60 percent of consumer automotive lubricant demand in 1995, today they represent about 40 percent.

There are many reasons for this decline, not the least of which is demographics and convenience. Its no longer fun for baby boomers, now approaching their golden years and enjoying center stage in terms of wealth, to crawl under a car to change oil. In fact, even their offspring, the Generation X- and Y-ers, are losing interest in changing oil. And why not? Its messy work, and after the deed is done you still have a gallon or so of dirty oil, a sloppy filter and oily rag to dispose of. In addition, its getting harder each year to change oil without a lift, specialized tools, insider knowledge and arms thin, long and limber enough to snake through the ever-tighter spaces under the hood. And if you dont think so, just try changing the oil on a Volvo turbo, a C5 Corvette, or even a new model Honda.

Repairs and warranty claims are also an issue. DIYers know they may be challenged if they change oil themselves and their engines later require warranty work. Sure, the automakers will honor warranties – but the DIYer better have the all the receipts available, and maybe even be ready to prove that the engine oil purchased was actually used in their vehicle.

For these and other reasons, the once-robust herd of DIYers continues to be thinned. Instead of changing oil themselves, DIYers are opting to have someone do-it-for-me.

So where are DIFMers taking their business, and how much lubricant do they consume? First, theyre turning to fast-lube centers, new car dealers, garages, gasoline stations, retail tire dealers, muffler shops, transmission shops, and other automotive repair shops. And as youd expect, the lions share of the lubricant sold to DIFMers is engine oil. Engine oil demand in this channel reached close to 400 million gallons last year, or 90 percent of the DIFM total. Transmission fluid accounts for close to 9 percent of the balance, and the remainder is gear oil and grease.

When it comes to lubricants, the largest installer segment serving DIFMers are the fast lubes. The nearly 11,000 fast-lube outlets in the United States moved an estimated 155 million gallons of lubricant in 2005, up from 135 million gallons in 1995. This represents an average annual growth rate of 1.4 percent over the period.

New car dealers are the second-leading DIFM outlet, and another growth segment. The combined demand from the countrys nearly 22,500 new car dealers reached an estimated 120 million gallons in 2005, up from 100 million gallons in 1995. This represents an average annual increase of 1.8 percent. Other growth segments in DIFM include mass merchants and auto parts stores with service bays – national names like Wal-Mart and Pep Boys, and regional ones such as Strauss Auto Parts.

Although growth in DIFM demand clearly has come at the expense of the DIY segment, there have been other casualties. Specifically, these include general repair garages and gasoline stations. Despite the shift from DIY to DIFM, lube demand in these types of outlets has declined over the past 10 years and is forecast to remain flat, at best, over the next five years.