So once again I'm bad at math when I buy stuff. Passat takes 5.8 quarts of oil so of course I buy a gallon and a quart (I know, bad at math).
Last night I'm changing the oil when this failure dawns on me. Normally this isn't an issue as I have extra quarts on the shelf in the garage. This time however, due to the sale going on at vatozone, I bought Castrol Syntec. Normally I use Mobil 1 so this is what I have extra quarts of.
So is there any reason why mixing two different brands would be bad? Both are "full synthetic" and rated for euro cars.
Synthetic, synthetic blend, dino oil, doesn't matter. They will all mix together.
Nope. Hell, I mix all the leftover partial quarts and jugs until I get enough for an oil change. Little Rotella, Mobil 1, havoline, etc. Different weights and brands and types. I use that jug in the small block chevy though.
In all honesty, as long as service grades both meet spec. It doesn't matter.
No reason not to mix brands or synthetic/fossil. You can even mix viscosities if you know what you're doing.
To carry the logic further, there is no reason to believe that 100% of the old oil actually drains out. Therefore, anytime you change brands, you are mixing oils, even if you are adding only one brand at a time.
You'll be fine.
if the engine ends up with new oil in it that's a normal viscosity then it will do just fine
