i live in MA where it gets cold during the winters but right now its the summer and i'm wondering if it's okay for my IS250 AWD to use 10w30 oil. my dad bought the valvoline full synthetic 10w30.

from what i know 10w30 will work fine as long as temperatures don't drop below 30? seeing that winter isn't until november, is it okay for me to use this oil until winter comes and change it back to 5w30? thanks.

 

That weight should be fine consult your owners manual to be sure it gives temp range and remember those numbers are viscosity ratings. Viscosity is resistance to flow, so you don't want high resistance to flow when it is cold.
I do recommend you decide what oil type & brand you will use for the life of your car & stick with it. I use Mobil 1 full synthetic