My car calls for oil 5w/20w I want to change it to 10w/30w or maybe just 20w

Paul, a few years late, but to answer your question I have to ask a question. Have you tried using synthetic? I use Castrol synthetic WITH a long life filter (important -- one that is designed to last longer than 3,000 miles or 3 months)? I tow about 2k with my CX-9 AWD and have used synthetic from the day I purchased it 3 years ago with 26,000 miles. Currently, I have 47,000 miles and never had any abnormal engine sounds nor any overheating issues. I live in the Pacific Northwest for what it matters.