Gaskets on the water pump and thermostat aren't very big deals, it's a lot better fate than most issues, and with a lift you're obviously going to lose MPG beyond epa rating, as with traveling 75-80mph. No vehicle gets ideal economy at that speed. Aggressive tires lost me near 5mpg alone, and I was only seeing 22-24 with a 6'4box 4wd crew. It still beats any gas pickup and I knew what I was doing