Good problem to have?
Not sure it's even a problem, just a "Huh..."
Never liked the mileage on my '03 Ranger 4.0 4x4. Going downhill, with a tailwind, driving like granny I might get 18mpg. 16 to 17ish was typical back in '03-05 when I was driving 100 miles a day for my commute.
Last few years I've worked mostly from home and haven't tracked the mileage.
Started a contract couple weeks ago that's 75 miles each way, and I thought I wasn't burning gas as quick as usual...especially since most of it is at 70-75mph.
Last fillup was 19mpg. Today's fill-up had me at 19.5mpg.
Hopefully it's just something to be thankful for and not something like a hidden hole on the air intake bypassing the air filter :D
Only three things I can think of is the Michelins I put on last year, I keep the pressure up pretty high on them; the last oil change I went with a full synthetic Valvoline...usually use Valvoline Durablend but Walmart had the full synthetic on sale for the same price (!); or with a 170,000 miles the truck is finally broken in.
I guess I'm just sharing a story unless anyone has an "Oh my God, that's a symptom of..." to warn me about improvements in mileage :)