Pennzoil Platinum seems to hold up well to high heat, high stress situations. I'd just stick with 5w30, both 10w30 and 5w30 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 5w30 year round and have never had any problems with it in my Tacoma.