I always turn it off (haven’t bought the eliminator for this truck yet, but I’ve used it on my last 3 trucks). I’ve been getting 17+ on almost every tank. I tend to drive more highway because I live in a more rural area. I’ve actually gotten a best of 22.9 on one trip. When I actually have had auto start/stop on, it does work with the AC but it’s based on load, so if it’s really hot outside and the system is commanding a lot of cooling, it will never stop the engine. But if it’s relatively cool, and the AC is on like 70, it will stop the engine every time.