Cruise Control and Fuel Consumption - Alfa Romeo Forum
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Cruise Control and Fuel Consumption

Does anyone know why the fuel consumption while the car is in cruise control going a steady 70mph on the flat varies so much? Starts out around 40mpg then drops to around 20mpg.
Does cruise control use more fueld than driving "manually" at the same speed?

Seems to use loads of fuel on cruise control which is a bit of a b*gger for long journeys

thanks in advance

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Never looked at the mpg while on cruise. Will have a look next time i switch it on.
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Cruise control keeps the speed constant but not the throttle.

70mph up hill requires a lot more throttle than 70mph on the flat so you will see the instant mpg disply changing.

In theory while maintaining a steady sped cruise control should be more economical than trying to do it yourself.

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I suspect the real differnce between you and cruise control is that if the cruise control system perceives a decrease in speed it will accelerate immediately to get back to speed even if it reqiures heavy throttle to do so.
You may decide that because of the situation it is better ito change down or mabe hold throttle at current position and let the speed fluctuate.

ie A criuse control system is a constant speed system which is not the best for fuel economy

A driver holding the throttle constant will get better fuel consumption figures than a cruise control unit. (however your speed will vary)
However I prefer to use cruise control as it is less tiring on long trips and you are less likely to get a speeding ticket with the associated loss of points.

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Normally , when you maintain the same speed by using your feet , you will be more consuming then by the CC . Why ??? because the cruise control just keeps the same speed . You just cannot keep your feet just as stable as the CC can . Even let's say 1/100 mm is a change in fuel to the engine , and you do that maybe every 1/10 sec , without you knowing it off course . If however you just want to use less , than the feet can keep +/- the same throttle position and the speed will go down when driving , uphill , windwards ... . The CC will then use more because it keeps the speed constant and adjust the throttle to maintain that .
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Apparently if you are doing 140km/hr on a 110 highway and you are in "Cruise Control".the cops just wave you on by!!
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thanks for the advice. The mpg definetly goes down whilst running on cruise control even on the completely flat straight motorway.
I will have to watch it and perhaps ask Alfa dealer when it goes in for a service.



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consumption , control , cruise , fuel

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