Originally Posted by SRL
How long the oil lasts depends on several factors: how long every day the oil remains heated, how hot the oil is heated to, how frequently the oil is filtered, the volume of food fried in the oil, salts and moisture in the food, etc.
True, in my post I explained my business, and that is how long you would expect your oil to last in this type of business. If your oil wasn't lasting the distance you would be doing something wrong and throwing money down the drain.
My usage was 100 litres a week give or take, the cookers started at 11am and closed at 8pm and ran @185C for six days. You do not replace all the oils at the same time, you start with fresh oil for your batters then work down the line to end with the crumb.
Any product that leeches blood into the oil is not good, any product that is just floured as the final coating is worse.