Well if you drive a GTP easy it will do better than 19. Granted I've never done it because the term drive easy doesnt exist to me, but Austin got 34mpg on a stock vehicle I know it can be done.
But I agree on the expensive part. But there comes a point where it stops breaking
And premium isn't much more than regular compared tank to tank. $46.50 for regular @ $3.10 a gallon. $52.50 for premium at $3.50 a gallon. That's 15 gallons. You're gonna waste $6 somewhere else anyway lol.