In the opening scene, when Deadpool is laying on the drums of fuel, he's wearing blue Crocs. But when Colossus comes to the apartment to retrieve him from the rubble, his feet and legs are shown in his black boots.
When the brakes on the prison rig are cut they leak hydraulic fluid making it unable to stop. A vehicle that of size and weight would definitely require air brakes which not only don't leak fluid but apply automatically if the air line is cut.
At the beginning of the film, Deadpool says he was on top of 2,000 gallons of gasoline. In fact, he laid on seven 55 gallon drums for a total of only 385 gallons, and several of the drums were labeled as kerosene. However Deadpool tends to exaggerate his statements and was just being dramatic.
The goof item below may give away important plot points.
Although Cable says that there's only one round left in his handgun before he retrieves it during the final fight, the slide reciprocates back into battery after he grabs and fires it. In reality, the slide of his pistol, a Walther Q5 Match, would lock back on an empty magazine after the last round is fired.