switching oil brands. will this be a issue
 

Ok i bought my 09 new and it's had nothing but valvoline 5/20 used in it.
doesn't burn any oil car has 42,000 on it...

i plan on keeping the car until at least 75-80,00
so i've got this wild hair to change over to mobil 1 for the remaining 40,000
concerned about the engine getting older etc. am i worrying to much and should just leave well enough alone. or could i mess something up.

thanks for any advice

You will be fine

Thanks I'll go that way.

5w20? Isn't that a little thin?

5w30 would be preferable, esp given you're not exactly in an extremely cold climate over there in Orange :)