What are some good ideas for promotions/coupons for Auto Repair shop?

My husband and I own a small auto repair shop. I send out postcards for various promotions – oil change reminders, thank you's and also a couple of other ones (holiday, spring special, etc). We normally offer a good deal on oil changes, free Starbucks card, free tire rotation/brake inspection, % off parts, etc. I NEED SOME NEW IDEAS! I don't like to do anything too far out (like when you see $89 per axle brakes, which means it is double to do them), just something that is fun and a good deal for us and them and will bring in our customers more often We have a good size customer list (about 3500) and usually we see about 1200 per year. Sometimes I send cards to just the customers who have been in recently and sometimes I send it to those who have not. Any ideas?? We are a fair shop, with fair prices and honest repairs. I would like some ideas that are catchy but believable! What are some promotions you have received from your mechanic? Something about saving fuel, saving money, etc?? Thank you for any help!!