Punch of Friendship is the thirtieth episode of Engine Sentai Go-Onger.
Sōsuke is curious as to what will happen when an Engine Soul is set into Go-Roader GT, and uses Speedor as the guinea pig, over the Engine's vehement protests. Speedor's energy is almost completely drained in the test and he becomes furious with Sōsuke for blindly rushing forth. Just then, Straw Banki attacks the city with his Bakuha Drink. The Go-on Wings battle him until he uses his Straw Scattershot missiles on the people. The Go-ongers arrive and help the Go-on Wings battle the Savage Machine Beast, but Go-on Red and Speedor are still arguing over the Go-Roader GT incident. Straw Banki is forced to retreat after he loses his Gai Aqua power-up drink. Sōsuke finds the Gai Aqua, and when he and Renn are examining the bottle, they both accidentally get drenched by the drink, which powers up evil tendencies. The Gai Aqua causes Sōsuke and Renn to lose their sense of justice and, now referring to themselves as Sōnoji and Kōsaka, they start pandering the Go-ongers as a for-profit organization in an insurance scam, much to Saki, Hant, and Gunpei's horror. Sōnoji and Kōsaka abandon their Engine partners and go on a crime spree. Miu tries to run damage control as Hiroto battles Sōnoji and Kōsaka. Hiroto lays out Kōsaka with a punch, reawakening Renn, but Sōnoji escapes. The Go-ongers, minus Go-on Red, and the Go-on Wings Team battle the powered-up Straw Banki and are trapped by him. Meanwhile, Bomper reminds the still-miffed Speedor of why he had chosen Sōsuke to be his partner. Speedor puts himself into the Go-Roader GT and engages the Action Mode to literally beat some sense into Sōnoji. With Sōsuke restored to normal, he and Speedor dub themselves the "Go-on Mach Team," free their teammates, and overpower Straw Banki. Straw Banki Industrial Revolutionizes, but Speedor is out of power, so Bus-on and Bearrv battle alongside Seiku-Oh and GunBir-Oh and eventually scrap Straw Banki. Afterwards, Sōsuke and Renn make amends for their misdeeds, starting with the people they had scammed for insurance money, and the Sutō siblings decide that they too are due apologies.