To add to that, if you've got a GPS, bring it along for the ride. Typically theres a setting to show you the FASTEST or SHORTEST route. One is based on time, the other is on distance.
I've used both, and often times the SHORTEST route doesn't give me the BEST route, but it can knock 25km off my route in some situation. Whether or not that 25km worth of fuel ends up being chewed up because I'm being told to go through a residential or commercial area with lots of stop lights, versus the 25km of highway travel, I can't be 100% certain.