Franchises will have a proven process of cleaning ovens that gives the best results for the franchise owner and customer. The best way to clean ovens is to strip the oven down and clean the whole oven removing every bit of grease and burnt on carbon using eco products that don't harm the user or oven. Safest Franchise systems have a van mounted electrically heated dip tank to dip in the dirtiest oven parts to get them clean.