I just got back from a cruise this weekend and managed 21.5 on my car if the gas tank filled up right. I've swapped to a T56 with a 0.5 overdrive some time ago and have continued to work on my tune. I have an aftermarket tank that never really knows when it's full though, so I'm never sure that I put the same amount of fuel in it each time I fill it since it will kick off auto-fill on most pumps early (like, right after you turn it on early). I ended up doing around 250 miles and change on 11.5 gallons, so I was pretty happy. All highway for the most part. 20 was the magic number I always wanted to hit, so seems it will do that on the highway at least.