My moms 2007 Kia Optima just rolled over 100,000 miles this morning!! The car has been on a steady diet of Mobil 1 5w20 with a purolator filter (either classic or pure one) throughout its life. There have been times where it's had some Castrol syntec or PP, but mostly Mobil 1 and ALWAYS 5w20. So the question is should we change to high mileage oil? The car doesn't burn a drop of oil or leak at all. My moms maintains it meticulously. The car sees freeway everyday and some shorter weekend errand runs. Opinions wanted