I have just started using mobile 1 EP in my 2000 Toyota camry. The car has 157k miles on it and is in good running order. My question is should I take a sample to send into Blackstone at 5k miles or 7.5k miles? I just want to make sure this oil is doing its job up to 15k miles and if not change it whenever it gets dangerous. I am using the new 20k mile oil filter they just came out with because that's the one it came with on the deal. My parents have used this oil in there 2005 camry since new so I have faith in it but I don't have faith in worn out parts and oil contamination. I hope someone can give me a little insight on this. Thanks.