Pennzoil Platinum seems to hold up well to high heat, high stress situations. I'd just stick with 5w-30, both 10w-30 and 5w-30 are the same exact thing at operating temperature. I'd prefer the 5w for better cold start flow, since 90% of all engine wear occurs during startup, oil flow would be my top priority. Summertime wouldn't matter which you use though, but I'd still stick with the 5w, just my preference. I run 5w-30 year round and have never had any problems with it in my Tacoma.