Was he drafting you most of the time? I learned alot about the wearing of tires when i raced NASCAR online.
Conserving tires by drafting behind the lead cars and applying part throttle to hold speed around corners = longer tire life.
When you are at full throttle in a corner it burns off the tires faster regardless of traction. Stress on the tires = more wear
Setups have a hand in it as well but unless your car is "poorly" setup i.e extreme camber or toe it won't have a large enough affect on tire wear.
Also how smooth you are at holding your line and avoiding "line break" i.e sliding up the track and turning harder to come back down, has an affect on tire life.
Just a couple ideas.