Can You Drive 55?

55 MPH

WOOD-TV: Could lower speeds spur gas efficiency?

With gas prices climbing, one Michigan lawmaker says its time to roll back the speed limit.

A Democrat from the east side of the state has introduced a resolution in the state house urging the federal government to enact a 55 mile per hour speed limit nationwide.

The government did just that in the 70’s during the oil crisis setting a 55 mile per hour speed limit to conserve gas.

That went up to 65 miles per hour in the 80’s, and was lifted altogether in the 90’s allowing states to set their own limits.

So far there has been no vote on the resolution.

And they have a poll on the subject. Here’s a screenshot:

The problem with this poll, and the 55 MPH speed limit resolution in particular, is that the slight mileage improvement that would result from a lowered speed limit will do nothing to change the price of gas. Not in a noticeable way. Sure, you may save a few bucks personally, and all of that savings will add up. But it’s not going to do much to increase the supply of oil/gasoline.

The number I usually seem to hear about the mileage benefits of a 55 MPH speed limit is “up to 15%.” So let’s say, for the sake of argument, that it really is 15% instead of the 5-10% that “up to 15%” probably really means.

If you’ve got a vehicle that gets 30 MPG and you drive 12,000 miles a year, you will burn about 400 gallons of gas getting wherever it is that you go. Up your mileage by 15% and you’ll be getting 34.5 MPG, saving yourself about 52 gallons of gas. At $4.00 a gallon, that’s 208 dollars, or about $4 per week.

You aren’t going to be buying many extra groceries each week for $4, and gas prices aren’t going to shift much (if at all) because of a tiny decrease in demand.

Meanwhile, gas tax revenues will fall, as will the profit of gas stations and oil companies. This decreased revenue will actually give governments and gasoline suppliers an incentive to RAISE prices to make up for lost income.

Recall that when a county-wide initiative to conserve water in the Atlanta, GA area succeeded in lowering water usage by 30%, the country hiked water rates to make up for the lost revenue. If water usage goes back up, do you think the country will lower rates accordingly?

The Peanut Farmer Drives 55

Here’s a hidden cost to drivers: Driving 12,000 miles at 55 MPH takes about 218 hours. But if you drive 70 MPH, it only takes 171 hours. In other words, to save $4 each week, you’ll need to spend 54 extra minutes driving each week. $4 for 54 minutes comes out to somewhere in the neighborhood of $4.40 per hour. Would you work for $4.40 per hour? Would you give up 54 minutes of family time or free time or sleep each week for $4?

The actual savings (and time cost) experienced by most drivers will be far less, as most people drive a large percentage of their miles on roads other than highways. So maybe you’ll save $1.75 per week. Is that worth lowering the national speed limit?

Personally, I spent the past three tanks of gas driving 65 MPH on the highway instead of my normal 70. I’m shifting back up to 70 for the next three tanks and will see if I notice any difference in my mileage.

I encourage people to do some math before deciding to go forward with this. If someone feels strongly about driving 55, I have a suggestion for them: Drive 55. No one’s stopping you.

Can I drive 55? Sure. Do I want to? I don’t know for sure, but I doubt it.

Do I want to have to? Not a chance.

UPDATE: Bram correctly points out that the federal government did not set a 55 mph speed limit in the 1970s. They actually set a new limit that the states were required to adopt if they wanted their national highway funds. It was a de facto federal speed limit, though Washington couldn’t just set the limits in each state on their own.

(Cross-posted from MichiBlogger.)


  1. The federal government DID NOT enact a 55 mile per hour speed limit nationwide in the 1970’s. Since the federal government has absolutely no authority to set speed limits (except place like military bases), they used highway funds to bludgeon states into lowering speed limits and raising drinking ages. It’s wrong! It runs counter to the spirit of federalist form of government. Tell the Feds to mind their own business, the states and the people should retain their rights.

  2. You’re correct, Bram. It was the ‘National Maximum Speed Law’ and did, as you said, threaten to withhold funds from states that did not comply. I do think the difference is important to note, so I added an update. Thanks.

  3. I’m an engineer and I can report from personal experience that driving slower speeds does not necessarily improve fuel economy. The last time we went through this nonsense, my 1969 Camaro went from 21-22 mpg @ 70 mph to 17-18 mpg @ 55 mph. . There are proven engineering principles to explain this phenomena. Internal combustion engines get their best economy at a certain speed; usually within a couple hundred rpm of the maximum torque rpm. Fuel consumption increases above or below that speed. The speed at which a vehicle gets its’ best economy is a function of the engine’s best economy speed and the final drive ratio. . In other words, the original 55 mph limit was feel-good legislation intended to make you ‘feel’ like you were doing something to save gas.

  4. Three things: 1, If I want to drive faster than 55 because I don’t give a sh*t if it costs me an extra $4 to get where I’m going so be it. The state can bugger off. 2, I guess no one’s legally stopping you from going 55 (unless there is a posted minimum), but if you drive much slower than 70 you’re a danger to yourself and others in most of CT and MA… 3, …although during rush hour anywhere on I95, I91, or the Mass Turnpike your average speed is about 12 mph, so it’s a moot point.

  5. The point JiD accurately makes has been previously made in Car & Driver and a number of other auto publications. My experience has been the same as his. ’98 Z28 Camaro/LS1 5 liter V8 300HP– 27mpg @ 70mph/cruise and 24mpg @ 55mph/cruise. Transmission & final drive ratios play a part too, as they help keep your engine in an optimum efficiency/speed range (usually predetermined by Engineers like JiD at the factory during development). ’03 Subaru WRX turbo 2 liter flat four 265HP (in modified form) exact same mileage figures as the Z28 at the same speeds. A BIG 10-4 to GL’s observation that just because the limit is 65 or 70, doesn’t mean you have to drive it. DUH!!! This whole drive slower AgitProp campaign is nothing more than an excuse for liberal socialist elements in the gov and their eco freak allies to gain more control over one more area of our lives. What’s that technical term I’m thinking off………………oh yea,……BITE ME!

  6. My car gets better fuel economy when I keep it around 2400 rpm, which corresponds to about 65 mph. If I ramp up to 80 mph, I start to pull over 3000 rpm and my economy declines from around 32 mpg to 26.

  7. Screw that. Living out west, everything is far from everything else. It took forever to get ANYwhere at 55! If you want to drive 55, go right ahead, but leave me out of it. My ’06 Matrix gets 39-40 on the highway, and that’s going 75+ on the interstate.

  8. Heck, I’m retired I don’t need to speed. A couple of years ago in July when I was living near Durham, NC I drove up to see family in mid-NJ. My car at the time was a 2000 Toyota Echo (now Yaris) with a 2.0 liter mill, auto and AC. I purposly kept a record of the mileage, gas consummed on the 500-mile trip. No I didn’t take Rte-95. It sucks big time, any time. I took Rte-84 from Durham up past Richmond, VA then hopped off on Rte-301 through Maryland and Delaware, then back roads through the NJ pinelands. I purposely tried to do 55-mph tops (staying in right lane) most of the journey. Anyway, when I arrived in Soprano land I calculated my gas consumption and was suprised to see it was 48 mpg. Jerry in Detroit is correct in a way. A Camaro with a big V-8 will probably get better mileage at 70 mph, but at the end of a pleasant, stress-free 500-miles I bet I used a heck of a lot less gas over all.

  9. I happily stumbled across this post while stumbling through the internet trying to find out what a Ridgback armored vehicle is. Anyway, it is unlikely that a modern, computer-controlled, fuel-injected vehicle will get worse gas mileage at a lower vs. higher speed. Unless the automatic transmission is faulty, or, in the case of of a manual transmission, the driver, you will get better gas mileage at a lower speed. The main reason higher speeds lead to higher fuel consumption is drag. Carbureted vehicles are speed dependent in that optimum air velocity providing the most efficient air/fuel mixture is in a very narrow band. My highway mileage in a 2007 VW GTI increased from about 29-30 mpg to 34-37 mpg during my 20 minute commute to work. As GeekLethal said, traveling less than that is a danger to both me and other drivers. However, just being able to pay for the increased gas price isn’t a justification for doing it. One of my reasons is to help reduce our country’s dependence on something that is controlled by lunatic countries like Iran and Venezuela. Therefore, in my mind, people speeding are in my mind anti-American, and need to put our country in front of their personal wishes.

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