I have been running Prestone All Makes All Models in my dad's 92 Toyota van for the last two years and 20k miles. Last week, when I checked the coolant condition, the coolant looked slightly rusty and had a lot sediment in it. This is despite using Prestone Super Radiator Cleaner during the last coolant flush. So on a whim, I bought two gallons of PEAK Extended Life 5/150 today at Walmart. $9.50/gal. I don't see any info about it on the PEAK website, so what is this stuff?