Modern engines are precision engineered and manufactured to exacting tolerances.  As a result engines burn less oil and are subject to less combustion blow-by which contaminates the oil.  So the days of the 3-month 3,000-mile oil change are over.  Most modern cars have a maintenence reminder or oil change light.  I recommend an oil change whenever this light comes on, or once a year if the light does not come on.  Most cars without an oil change light can safely go 5,000 miles on an oil change, but the level should be checked monthly. 

Most manufacturers do not recommend maintenance cleaning of fuel injectors.  Fuel injector flushing can be effective for repairing injectors clogged by poor quality fuel or other contaminates.  A far better solution for the average driver is to use a high quality, "Top Tier" rated gasoline, such as QT, Chevron, or Shell,  and a bottle of Techron in the gas tank at each oil change.

It seems every dealership and every independent shop has its own recommendations for your vehicle's maintenence.  I personally recommend you refer to the owners manual for your vehicle and follow the factory recommended maintenance schedule.   

The best fuel economy possible is the direct result of proper maintenance and good driving habits.  Two things to consider:

 · Air Filter- A vehicle that has a dirty air filter can’t efficiently draw air into the engine. This restriction forces the engine to expend energy to“breathe” wasting fuel in the process.

 · Tire Pressure- Set your vehicles tires to the manufacturers recommended pressure. This can usually be found in the drivers door jamb area on the tire placard.