9.1 qts or buy it in 3 gallons. if they're going to use the same process I used when I worked at Jiffy Lube, they arn't going to want to use a single qt bottle to extract fluid from 9.1 times. So just buy 3 gallons worth and let them flush 12 gallons through. It won't over fill it it'll just over FLUSH it and assure you that you have fresh clean fluid.