Ok guys, im at about 165miles into my 10gal costco fill up and still have a bit more than quarter tank. Now, since my last fill up, this week ive done about 65% city driving and 35% hwy driving. I know this might not justify my costco gas fill up test, because on my 200mi per tank was with 80% city driving and 20% hwy, but it was still worth a shot! So far, so good. Ill report back with the final outcome.