Home Depot has it for $21.xx per gallon.
My local Menards (60491) has it for $19.12.
Have Home Depot price match to Menards and use their price guarentee to get 10% off = $17.24
Then, send in the Home Depot 11% Rebate that matches Menards: $15.34
Then, send in the $5 per gallon Shell rebate (limit 4): $10.34
$41.36 for 4 gallons of T6 is pretty slick in my book.