## Saturday, August 9, 2014

### Fuel consumption of the Prius and the Corolla.

Prius versus Corolla fuel savings

Questions:

Gas mileage estimates for the Toyota Prius and the Toyota Corolla are presented below.

 Fuel Efficiency In Miles Per Gallon Toyota Prius Toyota Corolla City 51 30 Highway 48 42

Driving patterns defined by total miles driven in a year and percent of miles driven in city and in highway for six drivers are presented below.

 Six Driving Scenarios Driver # Miles Driven Per Year % City % Highway 1 10,000 25 75 2 10,000 75 25 3 12,500 25 75 4 12,500 75 25 5 15,000 25 75 6 15,000 75 25

How much gas would the six drivers use in a Prius and in Corolla over the course of a year?

How much would the six drivers spend on gas in the two cars at a price of \$3.50 per gallon?

How much would the six drivers spend in gas in the two cars if the price of gas was \$4.00 per gallon?

Analysis:

Discussion of Calculation:

Step One:  Obtain city and highway miles driven.  For driver one city miles = 0.25*10,000 and highway miles = 0.75*10,000.

Step Two:  Obtain gallons of gas consumed in city and highway.   (Note that gallons=mile/(miles/gallon).  So for the first Prius driver Prius City gallons = 2500/51  and highway gallon = 7500/48.

Step Three:  Add city gallons to highway gallons.  For the first Prius driver get 205.

Step Four:  Dollars spent on gas is \$/gallon x gallons.  Get \$718 at \$3.50 per gallon and \$821 at \$4.00 per gallon.

Results:

 Prius Calculations Ann Miles % City % Hway City Miles Hway Miles city mpg Hway mpg City Gals Hwy Gals Total Gals Gas @ \$3.5 Gas @ 4.0 1 10000 0.25 0.75 2500 7500 51 48 49 156 205 \$718 \$821 2 10000 0.75 0.25 7500 2500 51 48 147 52 199 \$697 \$797 3 12500 0.25 0.75 3125 9375 51 48 61 195 257 \$898 \$1,026 4 12500 0.75 0.25 9375 3125 51 48 184 65 249 \$871 \$996 5 15000 0.25 0.75 3750 11250 51 48 74 234 308 \$1,078 \$1,232 6 15000 0.75 0.25 11250 3750 51 48 221 78 299 \$1,045 \$1,195

 Corolla Calculations Ann Miles % City % Hway City Miles Hway Miles city mpg Hway mpg City Gals Hwy Gals Total Gals Gas @ \$3.5 Gas @ 4.0 1 10000 0.25 0.75 2500 7500 30 42 83 179 262 \$917 \$1,048 2 10000 0.75 0.25 7500 2500 30 42 250 60 310 \$1,083 \$1,238 3 12500 0.25 0.75 3125 9375 30 42 104 223 327 \$1,146 \$1,310 4 12500 0.75 0.25 9375 3125 30 42 313 74 387 \$1,354 \$1,548 5 15000 0.25 0.75 3750 11250 30 42 125 268 393 \$1,375 \$1,571 6 15000 0.75 0.25 11250 3750 30 42 375 89 464 \$1,625 \$1,857

 Potential Fuel Savings Prius over Corolla Gas @ \$3.5 Gas @ \$4.0 Corrolla Prius Diff. Corolla Prius Diff. \$917 \$718 \$198 \$1,048 \$821 \$227 \$1,083 \$697 \$386 \$1,238 \$797 \$442 \$1,146 \$898 \$248 \$1,310 \$1,026 \$283 \$1,354 \$871 \$483 \$1,548 \$996 \$552 \$1,375 \$1,078 \$297 \$1,571 \$1,232 \$340 \$1,625 \$1,045 \$580 \$1,857 \$1,195 \$662

Summary   Based on the assumptions used here the savings on fuel consumption from the use of a Prius instead of a Corolla range from \$198 to \$580 at \$3.50 gas to \$227 to \$662 at \$4.0 gas.

Concluding Remarks:

The analysis presented here relied on EPA estimates of fuel efficiency, which differ from on-read fuel efficiency.  On-road fuel efficiency rates are generally a lot lower than EPA estimates and on-road gas consumed varies across drivers.  I expect that differences between EPA estimate and real world driving performance is higher for the more fuel-efficient car.

The Prius costs more than Corolla.  The potential economic gain from purchasing one car over the other would look at additional purchase costs and the difference in the lifetime fuel costs.

The next post looks at the net present value of purchase costs and fuel costs.

#Prius
#Corolla
#fuel efficiency