Tire pressures are a very important key to higher fuel economy. The higher the pressure, the lower the rolling resistance, the higher the fuel economy. The absolute minimum you should use is the driver’s side door or owners manual recommended tire inflation criteria.
Oil types and amounts are another important key to higher FE . A proper amount of low kinematic viscosity oil can do wonders for not only longevity of your ICE but the FE your automobile may be capable of.
So what do you do with all this entire list of techniques? What we are attempting to achieve is changing the EPA’s 11 mile city test so as to travel the same 11 miles but under our constraints, not theirs. The EPA test has you come to 23 complete stops. We are going to try and achieve 0 stops over those same 11 miles! In the highway test, we are using a far superior setup and DWL within DWB to achieve greater than the EPA highway test across its 10 mile distance. In other words, we are changing the rules of the City and Highway test to match our own much higher FE goals, not the EPA’s lowly ones!
To read the entire article: http://www.cleanmpg.com/forums/showthread.php?t=1510