The following case study was conducted with a 1991 Honda Accord LX 4 cylinder 2.2 liter 5-speed manual that had 288,000 miles on the odometer by the conclusion of the study. The date of the study period is the six months from April 12, 2010 to October 11, 2010. The gas mileage for this vehicle has been carefully charted since that date, and is accompanied by a complete set of statistical analysis. The data was recorded in a relatively simple format on a standard sheet of college ruled paper; data fields included were the date of the gas transaction, price of gas, quantity purchased, amount of money spent, miles traveled on the tank, gas mileage, and some totaled statistics including total miles traveled, total money spent, total fuel economy, and average price per gallon.
From this careful chart of fuel transactions, some useful statistics have been deduced. Over the six month period, 14,914.1 miles were driven with the automobile. The Accord consumed 461.07 gallons of gasoline, cost $1,205.65 (with an average fuel price of $2.61 per gallon), and posted an average of 32.35 miles per gallon over the same distance and time (this is combined city and highway mileage). The government's fuel economy website, http://www.fueleconomy.gov/feg/findacar.htm, contains data about this car that shows it is performing very well, since they say the 15,000 mile period should have cost $1,775 for this car. If you conduct the same research experiment with your own car, you can couple the compiled data with your own intimate knowledge about your driving habits and vehicle maintenance. This can help you to understand for yourself what produces good gas mileage and the consequences for certain driving behavior.
Vehicle maintenance makes a difference! At the very end of the six month research period, the analyzed automobile received new NGK platinum spark plugs, a cleaned and recharged oil-impregnated air filter, and some other general maintenance. With six months of data and 31 gas fillups assembled on one sheet, the car still outperformed the best economy result on the page by nearly a full mpg with 36.7 miles per gallon on the final transaction!
Several implications can be drawn from this data.First, changing items like spark plugs and air filters at the recommended intervals makes a difference. Your car's engine will run smoother and more efficiently when this maintenance is performed.
The other implication is that the rate of travel is enormously important to your fuel economy. The record-breaking 36.7 mpg result was achieved traveling at 70 miles per hour on the interstate, but a number of results on the page came from traveling 80 mph on the same route, and only managed to produce 31 or 32 mpg. If you take your foot out of the gas pedal a bit and make the choice not to compete with the speedy flow of traffic, you will improve your gas mileage significantly and will also reduce the strain on engine and brake components. In the data stream of this example, the correlation is 100% consistent: the speedier the driving was and the more acceleration and braking occured, the worse the gas mileage got. You can improve your gas mileage if you take a lesson from this data.