When Johnny walks up to ask Roland if he can borrow his truck, Roland is mowing his front yard. You can loudly hear the sound of the mower running, and see exhaust smoke coming out of the machine. The mower is running at full speed (judging by the sound of the mower), yet little puffs of exhaust that are barely moving are seen coming out of the exhaust muffler. The smoke very apparently has been added in post-production with CGI, and the sound was added in, too. The lawn mower was obviously not running during the filming.