Cruise control better than man?

[Riley]

My brother and I got into a discussion the other day and I said I'd consult with my web gang to settle it. A friend of his (supposedly very smart about autos...) claimed that even a good driver can not get as good gas mileage as the cruise control can.

For example when cruising the highway, you will always get better mileage using the cruise control (assuming the traffic is not too congested). I disagreed. Sometime (mainly in hilly areas) the cruise control will do whatever to keep the speed pegged at the set point. However sometimes like on steep hills I'm ok with it slowing down a bit to climb that super steep hill. Do I really need to floor it and shift down ect.... just to keep it pegged?

I can see that in lots of cases (with lots of different drivers), the cruise control can do better but to make the claim that cruise control will ALWAYS get better mileage then even the best driver is incorrect (in my mind anyway).

What do you guys think, you want to settle this?

Riley

 

[Scamper]

I'm with you. On relatively flat/even roads, CC can't be beat. But on hills, I take the CC off and use the right foot.

 

[thorvald]

probably is better not using it on hills.

ive never liked cruise control much. on long trips the jerking of my foot on the gas helps keep me awake

 

[landtoy80]

Get one of those mpg meters or a meter that tells you gallons used and run a strech of road once with the cc and again with the foot.

 

[hoser]

Manual mode CAN get better gas mileage than cruise control especially when the road is hillly. You are correct that cruise control will do what it can to keep that speed even if it means full throttle. Full throttle=poor fuel economy.

CC will often get better fuel mileage on flat roads as it tends to feed fuel at a contstant rate as opposed to surges of fuel. I've noticed people tend to surge a lot when they are preoccupied or on the phone--I pass them up and sure enough, they are on their cell phone.

However to get the very BEST fuel mileage... Road & Track did a test 10 years ago with a Honda Civic VX that was rated at 50 mpg. They were able to drive it from San Francisco to Los Angeles AND back(total 720+ miles) on ONE TANK (9 gallons).

To do this, they very slowly accelerated to 35mph and then let it coast to 15mph and then back up again to 35mph--and repeated this process over and over. Never exceeding 35 because that's when wind resistance would have an impact. I can't remember if they overinflated the tires or removed weight but I think the vehicle was otherwise stock.

The best mileage they were able to get was something like 100+mpg and the lowest was about 75 mpg! Awesome, that's a 50-100% increase over their rated mileage.

 

[RavenTai]

I wonder how the hand throttle would do in hilly terain? set it to a constant throttle opening and the speed you get is what you get

 

[ELLTEE]

Manual control can get better gas milage in the mountains, especially if you're able to get up a head of steam on the downhills.
But if you're like me, and use the CC for speed control (fewer tickets, less points, lower insurance premiums) as much as for MPG, the CC beats manual control every time in every circumstance.

LT

 

[CDN_Cruiser]

I wonder how the hand throttle would do in hilly terain? set it to a constant throttle opening and the speed you get is what you get

...ya, I used to use the hand control 'cruise control' on my 60 every now and then...When it was 1600km to the next major town, you needed something!

 

[T Y L E R]

Good question Riley !

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Can anyone address gearing in all of this ? Is there an optimal rpm to cruise at in our 80's , for instance ... so within limits , could we pay attn to rpm VS speed to achieve better mileage ?

T

 

[Riley]

snip...
But if you're like me, and use the CC for speed control (fewer tickets, less points, lower insurance premiums) as much as for MPG, the CC beats manual control every time in every circumstance.

LT

I agree on the ticket aspect. In fact using CC is about the only way I can stay at the speed limit. The question was soley technical in nature. Hoser's got it nailed regarding hills ect.... more power required to keep speed up going up hills = less mpg.

 

[photogod]

Your best mpg will be at the max torque of your engine for the 80 in stock config. Say the max torque was in the 2200 rpm range then hypothetically the best mpg would be to run the engine at 2200 rpm at highway speed to attain best mpg... As explained to me by a corvette gearhead.