The average cost to fill a 20-gallon gas tank is $80. Photo by Tonya Torres: The Signal. MultimediaVideos VIDEO: Rising gas prices By The Signal Last updated Jun 15, 2017 128 0 The Signal reporter Mark Bownds takes a look at rising gas prices and how if affects college students. rising gas pricesvideo 0 128 Share EmailFacebookTwitterGoogle+ReddItWhatsApp