I did this on my wife's X-terra. I always ran Valvoline NexGen 5w-30 w/Mann filters at 5K miles. The samples always came back looking good and Blackstone would suggest running it to 7500 if I wanted. I switched to Royal Purple same weight and did the first change at 5k and it looked the same as the conventional. I ran it to 10k and Blackstone said I could go further if I wanted, but I never did. I just recently switched to Mobile 1 (it was on sale at Wally World) and the samples look identical at 10k, except for the additives. I recently changed the oil in my 4r to mobile one (same sale) I'm gonna run it to 10k and then go with whatever name brand syn is on sale at the time.