Thatherton Fuels is the crooked rival propane store of Strickland Propane. It was created by M.F. Thatherton, an ex-Strickland employee, to prove himself superior to Buck Strickland. The name is a bane to Hank Hill, as he often exclaims, "Thatherton!" when he hears of his wrongdoings.
According to Hank and Buck Strickland, in spite of its longrunning business, Thatherton Fuels has been placed on probation and censured by the Texas State Propane Association on multiple occasions. Compared to Strickland Propane and the other propane suppliers of Heimlich County, Thatherton Fuels is generally seen as second-rate, and is known to resort to shady or dishonest tactics to secure its business.
In the Season 4 episode "Rodeo Days," it is revealed by a rodeo announcer that one of Thatherton Fuels' slogans is "Selling the heat with warmth." Upon hearing this, Hank Hill displeasingly remarks that the slogan is a lie. In the Season 6 episode "Joust Like a Woman", Thatherton Fuels attempted to beat Strickland Propane to win an expensive propane deal by using the always-risky tactic of underbidding the low bid.
The tag line used in other parts of the series, and appearing on Adult Swim show promo spots is "Thatherton Fuels - When you want propane done right."