I use Castrol GTX 5w30 all year. Should I switch to 10w30 in the summer?

 

<div class='quotetop'>QUOTE (UltraTibby)</div><div class='quotemain'>I use Castrol Syntec Out Performance 10w40. I do a lot of highway driving and this keeps the engine temps way down.</div> that's what I've been looking for, something to keep my engine temps down. I might have to try that.


I use Mobil 1 with no problem. Change oil about every 6,000-8,000 miles or so. Switching to 5-w 30 for the winter but I usually use 10w30

I have 86,000 miles on my 2000 Tib.