Universal Muffler And Oil Type, Hopefully this is in the right place lol Options

[mariosdarkworld]

Ok well i was looking at my exhaust system looks like i have two cats. Im guessing idk. Does everyone that owns an st have this weird thing that looks like a cat (sorry not to familiar with them) it goes right after the header. Anyhow i live in AZ so I dont need two I only need one. My question is what is a good size tubing for this vehicle and whats a good but not to loud muffler cause i was thinking MagnaFlow and 2.5 tubing.... Magnaflows pretty inexpensive and i heard it on youtube so i think i may go with that but i am open to suggestions
Next question is it says to use 5w-30 on the manufacture specs but this car is old and has 163k so I was told to use 10w30 in the winter and 10w40 in the summer. What are your guys opinion?? sorry, i know i typed alot just thought it was necessary lol P.S. It gets like 115F here in AZ for normal temp during summer:(

[GriffGirl]

I hear Mobil1 Synthetic is the best thing to use in our cars... currently I'm using Castrol GTX Synthetic Blend, I honestly don't remember if it's 10w30 or 10w40, I wanna say 30 though... anyway, it's been pretty okay, seems to burn off a bit but then again I really need a new valve cover gasket, so I'm sure that's not helping any.

I'm a big proponent of synthetic blends (because they cost a little less than full synthetic) or synthetic in any car that's higher mileage. Generally speaking, just stick with name brands and you should be just fine. Half the crap comes from the same sources anyway I think!