The Eternal Road Trip Debate: Go Fast or Save Money?

January 29th, 2013
Road trip

It's all smiles to start!

It begins with loud music, fully stocked coffee cups and snack bags, and the excitement of leaving town and heading to a favorite destination for a few days of fun and relaxation.

Ahh… the road trip.

Soon enough, though, the miles pile on, the music gets turned down, the empty coffee cups mean full bladders and empty snack bags litter the car. The final destination doesn’t seem any nearer than when the trip started, and the urge to get there faster translates to a few nudges up in speed on the cruise control.

But what does speeding up from 70 mph to 80 mph mean for fuel consumption? Is getting there a little earlier worth the extra cost of fuel?

In all truth, at least from my perspective, yes.

I adore road trips. I crave them even, especially with a special someone to a secluded winery many miles away. Depending on the distance being traversed, though, I reach a point where I just want to be there, and I’d set the cruise at 100 mph and take 10 miles per gallon if that were an option.

A new study by Oak Ridge National Laboratory, which supplies fuel economy information to the fueleconomy.gov website, has completed testing on 74 vehicles at highway speeds of 50, 60, 70 and 80 miles per hour. The results are perhaps the most sleep-inducing set of data you’ll ever see, but the bottom line is interesting. Lucky for you, I’ll report the findings here and save you from an intensely scientific read. And maybe I’ll even save you a few bucks on your next road trip.

It’s no surprise, really, but increasing speed dramatically reduces fuel economy.

An increase from 50 to 60 mph reduces fuel economy on average between 10 and 14.3 percent.

Speeding up from 60 to 70 mph means an 11.2 to 16.1 percent drop.

Moving from 70 to 80 mph will cost between 12.5 and 17.5 percent.

The 74 vehicles that ORNL tested represented a wide range of models, including

various sizes of sedans, wagons, and SUVs, as well as pickup trucks, minivans and a few “muscle” and sports cars. Vehicles from model years 2003 to 2012 with a wide variety of powertrains were represented and included two hybrid sedans and a diesel sedan.

The final numbers shown above are the averages of all vehicles tested.

Once a modern vehicle gets close to the 80+-mph range, something called “protective enrichment” happens, which means a vehicle will inject more fuel in order to prevent the exhaust system from getting too hot. Once that happens, fuel economy can drop up to 26 percent.

The bottom line of all this is pretty obvious, but giving in to the temptation to increase highway speed can have a pretty sizable effect on the amount of fuel used on a road trip. So, the question is:

On a road trip, would you rather take the fuel penalty and get there faster, or save money and keep things slow and steady on the highway?

-tgriffith

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  1. Randy
    | #1

    I always plan my trips to give me plenty of time to get where I need to go at a safe speed and take some interesting side trips. I try to avoid really boring roads like I-70 through Kansas or ANY road in Texas to reduce the tempation to go over 70. As for speeding, don’t– You don’t want to find out what happens to out of state drivers pulled over for speeding.

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