Yea using heavier oil is a good idea. You might want to follow pleasdodgvan's suggestion, it has some merit.
However like pleasedodgevan I have the suggestion that you loose the quick lube places like the one you have been using. Keep away from the quick change places. We hear far too many horror stories about them. Some may be fine, but many pay the help little, demand fast changes and that results in a high percentage of errors. Too many live by selling you something you don't need at inflated prices.
Find a good local mechanic and stick with them for your needs.
Don't go to the quick lube places, even for directions.