The slow car movement........... Easing off the gas eases gas use

The slow car movement
Easing off the gas eases gas use
Posted by Eric de Place

A few weeks ago, Clark wrote about truck drivers slowing down to economize on fuel. It's a great story, but was it a real trend or just anecdotal?

Well, I'm here to report that there's some truth to it. Or at least some truthiness. A recent Congressional Budget Office paper examining the effects of gas prices found this: "Freeway motorists have adjusted to higher prices by making fewer trips and driving more slowly."

But whether it occurs to anyone or not, it is a rational response to high prices, depending on the circumstances. As the paper explains, slowing from 70 mph to 65 mph reduces a typical vehicle's fuel consumption by 8.2 percent. That adds up eventually, but whether it's worth it depends on how much you value your time. (It also depends on how pricey gas is, and how efficient your car is.)

http://gristmill.grist.org/story/2008/4/28/9216/56764


We all flinch at each uptick of gas prices, right? Well, factor in this rule of thumb: each 5 mph you drive over 60 mph is like paying an additional 20 cents per gallon for gas.

If the sweet spot for fuel efficiency is in the 50's, as the chart indicate, then as you get into the high 60's and above, the addition of each mph requires more fuel than the last. This is explained in greater detail at howstuffworks' article answering the question, "What speed should I drive to get maximum fuel efficiency?"

http://www.greenslowmovingvehicle.com/

Who gives a crap about time anymore in business? How are you going to make a profit anyway if your truck's fuel bill doubles?

This fantasy about time is money is so bogus in this age of gas approaching 4 USD

Less gas means a driver can offer lower rates. I've noticed the rigs that run between the grocery warehouses and stores have started driving ~50-55mph. According to Cummins that should save them a 30-40% in fuel costs. If a driver can do that and pass the savings onto the consumer they should be able to stay competitive, even if carriers can hedge against rising fuel prices to an extent.

Mine has bars that light up. The more bars lighting up the better I'm doing. So I choose to have that gauge showing all the time.

I do the worst when taking off at a light, so this is where I'm practicing vigilance. But this is just on side streets.

Most people have no problem passing me, I have only been honked at once or twice

luckily there is not much traffic

too bad this oil administration has not strongly encouraged folks to do the same

I have a Ford Escape Hybrid and went from 32psi to 38psi in the tires (well within the 44psi max rating of the tires). That extra 6psi allowed me to go from 33mpg to over 36mpg economy. I'm sure you'd get similar results with normal cars as well.

Driving more slowly helps as well, but one of the biggest savers I've found is accelerating slowly.

Alot of cars now are coming with transmissions with 5 or 6 gears, many of them can turn between 1500 and 2000rpm's around 60 to 65mph. Lower powered cars are usually geared shorter and will get better fuel milage at lower speeds. My 01 Trans Am with has a tall geared 6 speed manual, I cant even go into 6th gear untill I get well over 60 to avoid lugging the engine, effeciency hardly decreases untill probably over 75mph. Automatics will usually get better mpg at lower speeds. The automatic v6 Camaro I once had will go into overdrive at 45mph, I bet its probably where it can get its best fuel milage, but I never really drive that slow except if the speed limit forces me to, I wont know for sure since I sold it.

It will get even better fuel mileage at the peak efficiency rpm in 5th gear at 50 mph.

And it will get even better fuel mileage at the peak efficiency rpm in 4th gear at 42 mph.


Much below 40 mph, thermal losses begin to dominate (more energy per mile lost to heat).

It actually got worse fuel milage at lower speeds in lower gears. 1400rpm in 6th gear is running around 63mph, that same rpm range in 5th is running the car along at around 42mph. Add to the fact that my car is very aerodynamic so it easily cuts through the air, and has a torqy v8, it doesn't make much sense for me to slow down just for the sake of saving fuel. And no, I dont drive like a maniac, I rarely ever go anymore than 8mph over the limit when driving normally, and slower over the limit in town.

Their are alot variables to consider for different cars, to what type of engine it has, how much effecient torq it produces at low rpm's, the gearing, aerodynamics, the list goes on and on...

It goes down from there, though into the 60 and then 50 mpg range. So, since I live in a rural area on my little single lane farm roads I keep my mph within that range and then when on highways and in town I go the regular speed limit. I average 55 mpg this way. And I coast to stops as though I am riding a bike.

Getting old is funny. The news seems to be more and more recycled. All of a sudden there is talk of this new discovery: driving slower is more efficient (and safer too).

Of course driving 55 was once the law of the land, an example of big brother dictating how people live. As oil became plentiful after the availability shocks of the 1900s, it became ok to waste again. And waste we have.

I learned to drive with a mind towards conserving gas. Gentle acceleration, coast to a light, moderate speed. Kept my cars of moderate size. Just a silly old man now.

I cut my gasoline bill by 95%. Also save $$$ on auto insurance now.

55 mph limit on expressway.
Cars used to blow by me at 65 or better.
Not so much any more.