Ford I believe had Nox sensor issues thus extended warranty for years '11-'14 (I could be wrong). My '15 F350 was problem free when I traded it w/ 30K miles. My '17 F350 DRW also had the block heater cord replaced along w/ the DEF heater. Now I have a Nox sensor issue which Ford is trying to deny it's bad because their data says "That use of aftermarket fuel treatment can cause problems". It's been back to dealer 2x w/ same problem, going back for 3rd time tmrw. Funny thing here is, had DW take it to a dealer near her workplace and they said they couldn't fix it because they wouldn't get paid for it due to another dealer already having diagnosed it. Some warranty thing.