I <3 Cruise Control

[tplyons]

I drive 39.8 miles a day, each way, back and forth from work. That's 79.6 miles a day, and 398 miles a week, before errands and social visits.

Before cruise control, I was getting 26.55 miles per gallon (calculated by fuel at the pump, not by the onboard computer that reads about 3-5% high)

About this time last year, I made a realization. I knew I drove over 20,000 miles a year, and determined that at 26.55 mpg, I burn through about 780 gallons of gas a year. This accounted for $2,170 of my spending in 2010.

For a year, I used cruise control for my commute to and from work. No major changes in driving style other than using cruise control at 65 instead of driving at 71-72 mph. Not only did my commute become more peaceful, I managed to increase my fuel economy to 28.89 mpg, and only managed to get to work 2-3 minutes later than I had previously.

By slowing down and using cruise control, I increased my fuel mileage almost 9%. At 20,000 miles per year, my calculated fuel savings is approximately $235.66 or about 67 gallons of gas.

By using cruise control, I saved almost enough money to buy a Squier VM Jaguar bass.

Just some nerdy math that I figured out today. Long story short, I'll be keeping this resolution this year too

[MJ5150]

Slowing down on the road is good for everyone. Good job bro, and thank you.

-Mike

[Lee H]

I drive an F250 4x4, with a modified V10, a 3 inch lift and 35 inch tires...don't even mention mileage around me

[Pilgrim]

I use cruise by preference, as I want to travel a steady speed whenever possible. It's amazing how most drivers don't ever travel at a consistent speed!

But I don't slow down. I normally have more need to get where I'm going than to save gas. And on I-25 between here and Denver slowing down below normal traffic speeds can get you into frustrating traffic snarls. I watch ahead, and I usually speed up to get around traffic problems before they slow me down.

[oldrocker]

Surprised you can use cruise during your commute. Too much stop and go and traffic for me. Do you work off shifts?

[iamlowsound]

I used it when ever I can, it is a fantastic invention. I find the station that I fill up at has the most difference in my mileage. I have found one station where I can constantly get 38mpg in the winter from their gas, while a few other stations on my commute I only get 35mpg. Well worth the effort to fill up at the other station.

lowsound

[T-Bird]

Hi.

Drop off the cruise control as well and there'll be an additional 5% (if not more) efficiency increase.

Regards
Sam

[Let It Fall]

Originally Posted by T-Bird

Hi.

Drop off the cruise control as well and there'll be an additional 5% (if not more) efficiency increase.

Regards
Sam

If this is true why?

I know too much about vehicle efficiency as I'm a Hypermiler. Theron actually can be more efficient to speed up to a certain speed at a certain rate and then slow down. But to turn off cruise and do the exact same thing as with your foot changes nothing.

If you held a certain rpm while driving instead of a speed even uphill that would also be more efficient than a fixed speed.

[Lee H]

Originally Posted by Let It Fall

If this is true why?

I know too much about vehicle efficiency as I'm a Hypermiler. Theron actually can be more efficient to speed up to a certain speed at a certain rate and then slow down. But to turn off cruise and do the exact same thing as with your foot changes nothing.

If you held a certain rpm while driving instead of a speed even uphill that would also be more efficient than a fixed speed.

on cruise, the engine is not responding to your foot on the accelerator. It is responding to increases or decreases in intake manifold vacuum, and corresponding them to subsequent changes in load. This is truly very efficient on absolutely flat ground, but it is slow to respond to changes in load, because increases in intake manifold velocity can confuse the vacuum signal

[Let It Fall]

I'm still not tracking. Either way I'm almost positive newer vehicles track the speed via vehicle speed sensor. And may use vacuum to move the throttle plate or on newer electronic controlled throttles simply tell the computer to do it. Either way I don't see how the base statement that cruise control is less efficient without any other info can be true.

[Lee H]

Originally Posted by Let It Fall

I'm still not tracking. Either way I'm almost positive newer vehicles track the speed via vehicle speed sensor. And may use vacuum to move the throttle plate or on newer electronic controlled throttles simply tell the computer to do it. Either way I don't see how the base statement that cruise control is less efficient without any other info can be true.

speed is taken via magnetic sensor on the transmission. the throttle valve is still controlled by vacuum... vacuum signal is inconsistent, because it can intake velocity can cause variances in a smooth vacuum signal...as can things like the EGR valve interior heater controls, and a multitude of other things that bleed off the vacuum signal

EDit...maybe physics of an engine in laymans's terms will help
There is NO real vacuum in an engine. That is an agreed upon misnomer. When a piston goes down, the weight of atmospheric pressure pushes air into the area left by the movement of the piston. For engine mechanical purposes, average atmospheric weight is 14.7 lbs per square inch. This air movement is called vacuum, so you have a possibility of 14.7lbs of vacuum. Close the throttle valve, and it creates a venturi effect. Air speeds up, and the engines vacuum system "thinks" it gets more vacuum. The ecu calibrates fuel mixture upon a given formula of fuel necessary, for the amount of air entering, based on a throttle position sensor telling the computer how far the throttle valve is open. The O2 sensor in the exhaust takes readings and fine tunes the mixture. The computer also regulates the amount of vacuum, based on the air/fuel mixture.... when the cruise control is on, the throttle position switch is controlled by the vacuum, which is subject to change with load, and intake speed. It is a very highly inefficient way to calibrate air/fuel mixture

[tplyons]

Originally Posted by Pilgrim

I use cruise by preference, as I want to travel a steady speed whenever possible. It's amazing how most drivers don't ever travel at a consistent speed!

But I don't slow down. I normally have more need to get where I'm going than to save gas. And on I-25 between here and Denver slowing down below normal traffic speeds can get you into frustrating traffic snarls. I watch ahead, and I usually speed up to get around traffic problems before they slow me down.

True on all counts. I passed the same guy four times on a 20 mile stretch of highway. I'd blow past him in the right lane doing 65 while he's doing about 50 in the center lane, and about five minutes later, he's doing about 80 trying to play catch up.

And it's amazing how many people can't see upcoming issues.

Originally Posted by oldrocker

Surprised you can use cruise during your commute. Too much stop and go and traffic for me. Do you work off shifts?

I work 8-4:30... just far enough off of rush hour to avoid most traffic, and I have a reverse commute, driving away from the city.

Originally Posted by Let It Fall

If you held a certain rpm while driving instead of a speed even uphill that would also be more efficient than a fixed speed.

This is true. However, speeding up and slowing down doesn't work as well when the other people on the road are idiots. Honestly, I wish there was a hyper-miling lane. I'd totally be in it.

[Chebass88]

This is great to hear. I find it very hilarious when people gripe about high gas prices - WITHOUT doing anything about it.

I track my mileage with every tank of gas used, and drive conservatively. I exceed the "City" mileage every time!

[kanonfodr]

Meh, gas mileage should only be an indicator of engine performance, not some Holy Grail to attain. I drive with racing technique (at legal speeds) because that's maximizing the traction and options I have while minimizing risky points in the drive and generally keeping the idiots on the road from trying to kill me.

BTW, 98 Jeep Wrangler, 15 mpg avg. But it's paid off

Peace,
Greg

[Actium]

Driving around 65, cruise control or no, is much more fuel efficient than even driving at 70. The thing about cruise control is if you hit hills your rpm will spike as it overcompensates for the hill, eating more gas. In a flat area it wouldn't matter.

I don't remember where I read it but I did read something about 65-70 being a drop off point where your fuel efficiency for most cars plummets.

Your cars mpg is an indicator of how well everything is running. For example, if your tires are low on air and you leave it that way for a few months you lose 2-3 mpg regardless of how you drive.

[kanonfodr]

The 65-70 point is an old school myth, more applicable to big trucks that have lots of wind resistance. In reality I have come across several vehicles that get more efficient as you get faster (up to a point of course), including a mazda pickup that got 2 extra MPGs going between 80-95 on the Freeway versus cruising at 70.

Miles per gallon is exactly that, but if you are burning just a bit more fuel but covering ground much faster you are being more efficient. Modern vehicles are extensively wind-tunnel tested (a 2001 Toyota Prius has a drag coefficient of .29, the 1995 Ferrari F50 is about .372, lower is slippier ) to help maximize fuel economy and performance in this age of EPA regulations.

Also, for your tire pressure to have that massive of an effect on your gas mileage you would first have to have a really fuel efficient car, then have your tires pretty low. The highest number I have seen stated is 10% fuel economy hit, so for my Jeep that's 1.5 mpg. Maybe. In a Honda Civic, you MIGHT see that 2-3 mpgs, if your rims didn't carve up your tires first.

Peace,
Greg

[Let It Fall]

I find it hard to believe faster could be more effluent after 55-60mph.

[elgecko]

I don't like cruise control. I'm not a fan of robots driving my vehicle...I don't even like automatic transmission. BUT accelerating like a grandma and keeping tight reins over your top speed DOES do wonders for fuel economy. It's all about being aware of where your go pedal is at.

[mkandolf]

I love using cruise control and never understand shy people don't use it more often.

I use it religiously on my 45 mile commute and am getting historically 28-29MPG out of my 2008 Impala. I'll get 32-33 out of it on a trip.

Follow other vehicles at safe distances and watch your mileage creep up as well. Amazing how far back the draft actually is. I play with my information system and will find a sweet spot to ride in behind different vehicles.

And use the cruise +/- to increase/decrease you speed to match traffic as well. Get a read on what traffic is doing ahead of you and use it.

I really get aggravated nowadays when I get in situations where I can't use cruise.

[mkandolf]

BTW, most modern cruise controls are handles by the ECU's (Engine Control Unit and sensors), not vacuum.