Mixing Different Brand of Oil

[el guapo]

I saw a friend of mine do something yesterday that made me cringe. But it leads me to a question.

He was changing the oil in his Mazda 626 and was ready to fill it with oil when he pulled out three quarts of different brands of 10W30...two Pennzoil, one Castrol GTX, and one Quakerstate. I advised him against this and told him it would be best to use just one brand. But does it REALLY matter? The are all the same weight, all SL/Energy Conserving rated, and all "dino" oil (non synthetic).

Any thoughts on this?

[Mole]

eh... i'd say just stick to 1 brand per oil change.

i personally only use mobil 1, however during different times of the year, i may switch weights but still the same company.