While I'm no Civic expert, I've never heard of warmups or idling helping fuel economy. The engine has to warm up, no way around that. If you're moving, at least you get some useful work during warmup. Low MPG is better than No MPG! Plus, idiling only warms the engine, all the cars other components (transmission, drivetrain, etc) warm up only with motion. Modern engines warm up best best while driven (gently). They probably don't like hard acceleration or going 65MPH until they wake up, but wake up faster by getting out of bed!