Jezz. You guys are really stuck in your ways. Idleing temps are not that far off from full power temps, and the modern ABC engines don't care as much as many posting here do. The only bad thing about breaking in an engine at idle is it takes longer to break in. Most likely, being a car engine it simply injested some dirt. Or with that low oil fuel washed the machine oil off and it just seems tighter because of less lube.