Speed and gas mileage

I was doing errands with mrs crusty, and i remarked about people not slowing down on highways due to the high price of gas, and mrs crusty said that people don’t know that driving speed and mileage are related. any thoughts about that?

Americans were never great at getting a good science education and of course that’s gotten much worse in recent years, so unfortunately that wouldn’t surprise me.


I think overdrive and 8 speed transmissions changed the need for a 55 mph interstate speed.

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Mrs. Crusty is unfortunately correct. The majority of the folks out there don’t even know how to check their oil.

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Sure, I’m well aware that if I slowed from 75 mph to 65 mph I’d save some fuel and money. I’d also constantly be getting blown off the road by everyone else who’s running 80 plus. The savings aren’t worth it to me.


I have no idea what I must be doing wrong . Both of our vehicles get decent mpg at 65 mph . I have been to most of the US and never had trouble driving the speed limit . Here in Oklahoma the turnpikes are 75 and I don’t fear death at 65 or even the short stretches of 80 mph .

When I was still driving, I kept my speed at 55 on highways as a means of both conserving fuel and minimizing strain on the car.

They’d get even better mileage at 55. So, slow down some more if you want. I’d rather drive with the rest of traffic and spend the extra $5 a week.


If your car is that unstable, get it fixed. Why white knuckle it if you don’t have to?

I feel a certain satisfaction when I am enjoying a relatively calm cruise and someone comes past too fast and too loud. It must be exhausting for them after the exhilaration wears off, but that’s not my problem.

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I rented a 4 cyl straight stick. At highway speed it was turning 3000 rpm. My V6 s turn 1800 to 2000 rpm at the same speed. Do what you want though. Just another excuse for people that like to tell others what to do.

I think most people know that speed and fuel economy factor into each other. But I also think that modern cars still get good enough fuel economy at higher speed vs say a brick shaped 80’s GM A-body with 3 speed automatic, that the trade off isn’t worth it. At 75-80 mph my Mustang gets between 25 and 26 MPG, at 65-70 mph it goes up to a bit over 27 MPG and at 55-65 mph thrift reaches upwards of 28 MPG. Now doing 50-55 MPH on an interstate probably isn’t a grand idea. You could theoretically run 65 MPH , but with a modern car you’re giving up maybe 2-3 MPG, that’s not enough to change most people’s habits. It’s not enough to change mine. Of course the difference varies from vehicle to vehicle , your mileage will literally vary.


Which vehicle has the greater drag and fuel consumption at highway speed? The tachometer is not an indicator of fuel consumption, the four-cylinder engine might be half the displacement of the V6 but turning 50% faster.

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On second reading I think I understand what you mean, that you are surprised drivers are continuing to drive as fast as before the gas price increase, given that driving slower would likely improve their mpg and gas expense. hmmmmm … you are certainly correct that driving slower would burn less gas, but on a practical level I think most drivers who want to decrease their gasoline bill prefer to do that by just driving fewer miles, not by changing their driving style and speed. A lot of car trips are optional, not absolutely necessary, so it is easier when facing high gasoline prices to just eliminate those from the mix. Me, for example, currently my only vehicle I have available to use is my 15 mpg truck. So I ride my bike to do errands. That’s my primary mode of transportation. The folks who suffer from this change of behavior are the businesses that I’d normally be visiting.

Just anecdotal evidence. My cars cars shifts into overdrive at 60 or 65, yes I see all the charts proving otherwise , but for me no significant change going 68 or 78.

Mrs Crusty is right, I have a 2007 Silverado that my son drives a lot. When he drives it, it gets about 16mpg, when I drive it, I get close to 18 mpg. We both drive at around the same speed, but he varies his speed more than I do and accelerates faster. Since it is a 4 speed auto, all the benefits of the newer transmission do not apply.

Now I recently bought a 2020 Nissan Frontier with a 3.8 V-6 and 9 speed auto. I have taken it on a 4 lane road at a time when there were almost no vehicles as far as the eye can see. I accelerated slowly noting when each gear change occurred. It didn’t go into 9th until I was a little above 60 so in this case, it actually might get better mileage at 65 than 55, but that would be hard to tell the difference.

I suppose I could go back to that road with instantaneous MPG selected on the dash display and run the flat section at 55 and then at 65 and see.

None of my cars are unstable and I’m not white knuckling anything. I just prefer to move along with the speed of traffic rather than constantly getting passed and tailgated in order to get 1 or 2 mpg’s better.

Bear in mind, I still get passed quite a bit driving around 72-75. Drop the speed to 65 and you’re kind of in the way. Drop it to 55, and I think I’d actually be a road hazard.


Here we are again with all the gas saving tips. You could wait until the wind is blowing in the right direction. In the old days I taped a couple cow magnets on the fuel. Line just before the carb. That was one of the tips. Didn’t help but they are great magnets. I did about 1600 miles between 75 and 80 and didn’t notice any measurable difference in mileage. But everyone should do as they want.

On my route 95 in northern Maine from Orono (just north of Bangor) to Houlton it used to be torture if you had to go 55 mph. Now, at 75 you can cover the distance in one hour and thirty minutes. At 55 it took two hours and ten minutes. I thought about slowing down once but I would rather save the time on that stretch of road. I hope the speed limit never goes back down. Locally I just remain calm and do the speed limit anyway.

Most folks do know that high speed equates to greater gas consumption (lower mileage) and they do not care… That helps to explain why folks will pay $5 just for cup of coffee…

Somewhat, but wind resistance increases exponentially with speed.
Our local expressway has a 55 MPH speed limit and I am usuall going 64 and I tay out of the left lane and a steady stream od large pickup and suv’s stream past me at 80 and up. Neither gas prices or the massive amount of tickets handed out on our I-290 seems to have any effect on the speed of traffic.

The speeders don’t upset me, I don’t thpmk many accidents are caused by speeding. I think most are caused by not paying attention and drinking or drugs. SpeedeRs are usually paying attention.