Sears is very good at giving away 10% off coupons or $10 off coupons; so why not give customers who come in for auto service 10% off coupons for Sears so they can go shop while their car is being worked on.
Or, they could give a coupon when you drop off the car that gives X% off the auto service with a minimum in-store purchase of $Y or more while they wait (or something similar).