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Cruise control and mpg


VelvetblackCT
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Hi everyone,

I'm going to do a lengthy (400 mile) South Wales to London (M4) round trip on Saturday, and I haven't yet experimented with the cruise control on the CT. Could I ask what people's opinion / experience is as far as fuel economy is concerned? I've had a number of cars with cruise in the past, and the efficiency varied dramatically, from those in which it seemed to hit economy hard, to those where it seemed to do a better job of managing the fuel than I could! I've never tried it with a CVT transmission, though.

I'd be grateful for any thoughts or observations. Whether in cruise or not, I would be driving at a very steady 70 -75. 

Thanks,

Nick 

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I do many journeys on the M4 driving 70-75 too and I always use cruise when possible.  I have the IS250 and it usually returns 35 to 38mpg.

 

Something I'm unsure of though.  In the steep areas (ie Sarn Park, Bath), it will drop a gear and often two down to fourth in order to maintain speed.  I've not tried it, but I'm sure I could coax the car along without dropping lower than fifth gear.  I'm not sure if the cruise control is basing its gear selection on optimum economy or not ?

Overall, I'm certain that the computer can operate the controls far more smoothly than my right foot, so I'll continue to use cruise.  Report back with your experience please Nick.

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with cruise control it cannot forsee any upcomming gradients so if you know the road is going uphill slightly

use the accelerator to assist this way you can normally still stay in the eco section on the guage

rather than the cruise taking you into the power section and using more fuel.

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I probably use cruise control for every journey. The main function which I use it for is staying within the speed limit in 30 , 40 or 50 limits. For high speed cruising I use my foot to regulate the throttle because cruise control doesnt react to traffic conditions as I would want it to and I end up fiddling around with the lever in order to ease off or edge the speed up a bit meaning that I use my fingers to operate the throttle rather than my foot. Travelling at 70 to 75 wont get you in trouble with speed cameras on the motorway because this translates to about 63 to 68 in real terms. However, you will find that you have a fair amount of lane swapping to do because of the people who like to travel at 77 to 83mph ( 70 to 75 mph in real terms on my speedometer) I guess that driving an old car with manual controls will be ok in years to come when driverless cars become popular. 

 

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Thanks, guys - I sort-of suspected that a relatively low-powered CVT auto wouldn't be an ideal partner for cruise control. I might experiment, or I might just play the how-high-can-I-get-the-average mpg game with a feather-light right foot! 

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There are some distinctions to make about cruise control systems: in traditional CCs the simple function is to keep a fixed speed, so the only disadvantage comparing human control of speed is in situation where speed has to be varied for a better fuel use, i.e. in  intense traffic or driving up and down hills; so it's possible to achieve good and sometimes better mpg.

In new CC systems with adaptive logic, speed may vary with vehicle car is seeking, it's quite comfortable as you have no need to brake or accelerate in queue, but usually CC restores set speed in a fast way, and this is not good for fuel spare, so mpg rise compared to a human quiet ride.

So, generally speaking, CC in no traffic helps to spare gasoline, in intense traffic not.

 

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