I recently changed the coolant in my 2001 diesel JD tractor. 43 horse power small tractor. Out peak conventional that I put in 4 yrs ago when I busted radiator. Coolant came out like new. No discoloration only small amount of rusty stuff from engine block drain. All this removed by several flushes and runs with regular water then two flushes with distilled. Which is over kill on drains as engine drain really pulls most out that dont come out of rad.Now I put in 50/50 delo extended life coolant which is an (red) oat formula with sca's already in it. It does contain nitrates but no silicates or phosphate. My question was this ok since it's a heavy duty antifreeze. By the way I get this delo stuff free at work.