It has been discussed before about mixing brands and weights of oils together to come up with a "perfect" home brew. I'm actually asking about this because I have 7 different bottles of oil in my basement that I want to get rid of. I will be ordering some Amsoil ATM this week, and in the mean time wanted to flush my truck with the following: 1/2 qrt of M1 0w-40 1 qrt of M1 10w-30 1 qrt of GC 0w-30 1 qrt of Penz. 5w-30 1 qrt of QC full syn 10w-30 2 qrts of Delo 15w-40 This oil change is to serve two purposes. One is to get that retched RP 5w-20 out of my truck. The truck is noticably tapping and clicking and vibrating all the time now. I will be sending a sample in, however the noise is really starting to concern me now. Second, I really need to get rid of all these lone bottles of oil. The reason I have them to begin with is that I usually buy an extra bottle to top up with when I do a change. Ironically the only oil I needed to top up with is the RP 5w-20 ( a full qrt) and M1 0w-40 (1/2 qrt). OK - now to my question. Will there be any harm in running this mix for a couple weeks? Does anyone think that the oils will react badly with each other?