With the price of gas these days, you never want to see your gas gauge drop down to “E”. But with the Tank Up Coffee Mug, filling up is as easy and inexpensive as heading over to your coffee pot and pouring yourself a fresh cup. The “gas” gauge on this mug is heat sensitive and as you fill it with a hot beverage the gauge turns red and climbs up to full (and vice versa as you drink it). Side benefit is you can see how much coffee you have left from across the room- that is if you can actually put down your mug for long enough to head across the room without it. Tank up!