It's been said some people have an aversion to doctors, but mechanics? A recently released study shows U.S. personal vehicles are having fewer tune-ups, dropping to 39% last year versus 61% in 1996.

A spokesman for the Motor & Equipment Manufacturers Assn. (MEMA) attributed the decline to changing automotive technology, such as on-board diagnostic computers, but also the fact that car owners are putting off voluntary auto maintenance.

MEMA's annual analysis of U.S. automotive maintenance, Market Analysis of Replacement Rates of U.S. Automotive Parts 2001, shows there have been declines not only in tune-ups but associated parts, such as distributor caps, ignition wires and spark plugs — and discretionary maintenance such as shock absorber replacement.

MEMA has been publishing a Replacement Rates pocket card since 1999. The card details the number of privately owned, light vehicles in use from 1996 to 2000 and shows the incidence of component replacement and service jobs for those years. It also shows percentage change in 54 services from 1996 to 2000 and explains how to use the calculations and the existing replacement rate percentages.

The 2001 edition has new categories regarding scheduled maintenance at the dealership and the number of cylinders per vehicle. The cost of the card is $50 for non-MEMA members.