Comments on: Can You Drive 55?

By: Ted

Ted — Tue, 01 Jul 2008 13:36:00 +0000

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.

By: Sam

Sam — Tue, 01 Jul 2008 00:09:00 +0000

Jerry is correct, cars have different optimum cruise speeds. If Big-Gubmint ActionG

By: Toejam

Toejam — Sat, 28 Jun 2008 02:35:00 +0000

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.

By: Darrell

Darrell — Fri, 27 Jun 2008 21:20:00 +0000

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.

By: 11 Bravo

11 Bravo — Fri, 27 Jun 2008 20:15:00 +0000

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.

By: Flanker

Flanker — Fri, 27 Jun 2008 17:47:00 +0000

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!

By: Jerry in Detroit

Jerry in Detroit — Fri, 27 Jun 2008 15:38:00 +0000

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.

By: GeekLethal

GeekLethal — Fri, 27 Jun 2008 15:38:00 +0000

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.

By: Bram

Bram — Fri, 27 Jun 2008 14:40:00 +0000

Thanks – I think I’m the last Federalist left.

By: Murdoc

Murdoc — Fri, 27 Jun 2008 14:06:00 +0000

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.