Monday, May 27, 2019

Fuel Efficiency Improvements and Gas Consumption Reductions

This question considers impact of fuel efficiency changes on small and standard vehicles.


Question:   Below are the EPA measures of the least and most-fuel efficient small SUV and standard SUV.

How much gas is saved by a driver who drives 10,000 miles per year switching from the least fuel-efficient small SUV to the most fuel efficient small SUV?  

How much gas is saved by a driver who drives 10,000 miles per year switching from the least fuel efficient standard SUV to the most fuel efficient standard SUV?

How high would the small SUV fuel efficiency have to rise so that the net savings in gas from the switch in vehicle choice would be identical to the improvement that occurred in the standard SUV category?


Lowest EPA Fuel Efficiency
Highest EPA Fuel Efficiency
Small SUV
16
31
Standard SUV
13
26




Answer:   The gas consumed is miles/mpg.   Take 10,000 and divide by mpg in the above chart to get: 



Gas Consumed Least Efficient
Gas Consumed Most Efficient
Gas Saved
from Shift
Small SUV
625
322.6
302.4
Standard SUV
769.2
384.6
384.6




The amount of gas saved by converting from the low fuel-efficient to the high fuel-efficient vehicle is around 82 gallons greater when the conversion is done in the standard SUV category rather than the small SUV category.


The gas savings in the standard SUV category was 384.6 gallons.   For this to happen in the small SUV category the high fuel-efficiency small SUV would need to run 10,000 miles on 240.4 gallons  (625.0 – 384.6).   

The required fuel efficiency is 10000 miles/240.4 gallons or 41.6 mpg. 

Sometime a relatively small improvement in fuel efficiency for standard or large cars can result in a larger fuel savings than a large improvement in fuel efficiency for small cars.

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