ive installed it like after a year since new, yes i did some test on it too, am in the oil refinery company, compared the new amsoil viscocity to the oil that i drained, and its pretty damn close to new oil, also just for the heck of it i ran a BSW to check on the sediment nothing, so its great, i can even prolong the oil change per amsoil 25K or 1 year, and replace the eao15 every 6 months, but am playing safe am doing it every 6 mos,