I need to buy some dexcool to top off the reserve tank. Is there any issue in buying Autozone's Dexcool 50/50 version versus say buying the Prestone version for $5 more ? Also whats the reccomended flush interval ? While mine is a 2008 it really didn't get any mileage on it till 2010 when I bought it with 2800 miles on . It now has about 32000 miles on it . Does anyone really let it go to 100K before changing ? Or do you just change it at 5 years no matter what.Vehicle really doesn't see any heavy duty use , pulls a boat trailer about 40 miles a year , the rest is going back and forth to work and 3 hour trips to camp in the summer .