on Apr 6th, 2009 in Mail Processing & Transportation | 14 comments

Two families trade in their vehicles for more fuel-efficient ones. If both travel the same amount each year, which will save more fuel by making the change?

• Family 1 decides to trade in their 4-wheel drive Jeep Patriot (25.5 avg. MPG) for a Civic Hybrid (42.5 avg. MPG).
• Family 2 decides to trade in their 4-wheel drive Chevy Trailblazer (14 avg. MPG) for a 4-wheel drive Jeep Patriot (25.5 avg. MPG).

Please vote before continuing if you don’t want to cheat.

Did most of you think Family 1?

Well . . . that is wrong by a long shot. In fact, Family 2 will save more than twice as much fuel as Family 1! The problem here, however, is not you – it is the poor metric of MPG (miles per gallon).

If you don’t believe us, let’s do the math. Assume both families drive 10,000 miles per year.

Family 1 goes from buying 392 gallons of gas per year (10,000 miles / 25.5 MPG) to buying 235 gallons of gas per year (10,000 miles / 42.5 MPG) — resulting in an annual fuel savings of 157 gallons.

Family 2 goes from buying 714 gallons of gas per year (10,000 miles / 14 MPG) to buying 392 gallons of gas per year (10,000 miles / 25.5 MPG) — resulting in annual fuel savings of 322 gallons – or more than twice as many gallons as Family 1.

What does this mean to the Postal Service? The best way the Postal Service (or any organization for that matter) can save fuel is to find the least efficient vehicles and replace them with modestly fuel efficient vehicles. Small changes can mean incredible savings. Use the math above to prove to yourself that raising a truck from 5 to 6 MPG will save more fuel than raising a car from 20 to 50 MPG! Also, prove to yourself that raising that truck from 5 to 10 MPG will save more than twice as much fuel as making a 20 MPG vehicle use no fuel whatsoever!!!

Do you have any ideas about how the Postal Service can use fuel more efficiently?

Your analysis is incomplete. If family 2 gave up their gas guzzler for the hybrid, they would save 479 gallons per year, more than your example. You are correct that giving up gas guzzlers is crucial to the nation's fuel efficiency, but you should take the analysis all the way.

That's fine but not the entire story. Factoring in the purchase price of each vehicle, even without any extras, excluding all finance costs, and calculating the cost of fuel at \$2 - \$4 a gallon it would take at least 6 (family 2 at \$4 a gal) and as many as 20 years (Family 1 at \$2 a gallon) to see one dollar of savings.

This is not a simple issue. Tire pressure always gets a lot of attention, truth is the savings per year is slim, less than \$30 a year. A reduction in speed can increase fuel efficiency as much as 35% for the average driver. With the stop and go type of driving the USPS does I am not sure that suggestion is much help.

What ever happened to walking routes?

"S Says" is correct if the scenario presented is a plausible option -- I wish it was! But how many 4-wheel drivers are willing to trade-in to a hybrid? Highly unlikely. And the smae applies to the Postal Service. It's highly unlikely that the Postal Service would be able to trade-in all their LLVs into hybrid vehicles; but they can trade them in with relatively more efficient ones over time.

Lpeters...Walking routes are less time efficient than curbside delivery. You are correct that the stop and go driving significiantly drops the fuel milage. As a rural mail carrier, who must supply their own vehicle, we must have one large enough to carry all the mail and packages. Often a smaller, fuel efficient vehicle just isn't big enough. Many of us also need a 4WD vehicle for when we get stuck on back country roads, soft sand in the south, snow and ice up north. Second trips to reload aren't cost effective on many routes, which begin 10 miles from the post office. You also need a vehicle which will stand up to poor road conditions, a transmission package that can handle idling and stop and go well, and an engine that won't overheat under these conditions.

No wonder the postal service is setting a new record defict... The goal should be to minimize the expenditure.

If the hybrid was used in mounted delivery, in the same way that an LLV is currently used, the speed would be slow enough that a hybrid vehicle, such as a Prius, would use no fuel, only the battery. Gas is used only at higher speeds or once the battery is depleted. Using MPG as the only factor is limiting to say the least. Like using volume to determine route time, using MPG as the basis for estimating fuel savings is simplistic and unrealistic at best.

with mail volume dropping why cant they put two carriers mail volume in one longlife. all offices have 1 extra vehicle for emerg purposes.many times this extra vehicle is a minivan. this vehicle can serve as the taxi to transport multiple carriers to strategic points to drop off carriers who pick up their mail from the longlife. this could be assisted by utilizing the green boxes on street corners. also carriers can load their bag up before they leave the office with their first loop to make more room in the long life. this could theoretcially cut the longlife force in half. many times there can be 2 or 3 longlifes parked less than a block from each other. think about it.. no purchase of new vehicles. vehicles not being used can be garaged for future use as existing long lifes die. gas useage cut in half.. its not hard to figure this out.. i am a clerk and i can do it given the proper time and assistance from veteran carriers. i am sure they would not object to this. no jobs effected, gas savings, vehicle savings.

Josh makes a good point. It would also help out the American automakers by increasing the volume of hybrid cars that they sell, in turn driving down the price for other consumers, eventually making them affordable to more people. Then the demand for them increases, and so on.... A good way to get the automakers back on track and be more ecompetitive. No more need to buy hybrids from Japan.

And a good example for the Postal service to set for the American people.

I agree with you guys...

This is a very interesting idea. Note the links below which describe the same basic topic:

http://www.mpgillusion.com/