Is Cruise Control Economical?
- Thread starter DavidS
- Start date
how is that possible?, it uses more revs than 6th at same speed!!!! thus more fuel????????????????
It all depends what revs the sweet spot is.
Lower revs doesn't always mean lower fuel consumption. try driving in 6th at say 1200 revs, (probably about 45MPH) it will be about the same MPG as driving at 45MPH in second.
The sweet spot on a diesel will be ~1800 revs. 1800 revs in 6th gear is about 63 MPH in my Leon.
Last edited:
In theory you can get better by doing it manually (cruise control has no anticipation of events ahead of you), but I always cruise at 60 and just relax. I can get 40-42mpg out of my TFSI FR like that.
It also removes the "I'm bored, let's go a bit faster" that I used to get without cruise. And then I discover that driving really fast on the motorway is just as boring as driving slowly.
The thing I like best is the fact that I'm completely unstressed after a long trip.
It also removes the "I'm bored, let's go a bit faster" that I used to get without cruise. And then I discover that driving really fast on the motorway is just as boring as driving slowly.
The thing I like best is the fact that I'm completely unstressed after a long trip.
Cruise Control to me uses more fuel.
Back in 2010 when I had my Octavia vRS, a few of us went to Nurburgring and one guy had same car as me. He drove with cruise control on and I didn't. He managed 41 mpg and I managed 44.7mpg.
Back in 2010 when I had my Octavia vRS, a few of us went to Nurburgring and one guy had same car as me. He drove with cruise control on and I didn't. He managed 41 mpg and I managed 44.7mpg.
Thinking about it when it comes to MPG the cruise function must not be as frugal if you have activated it....iv read that even having the radio on can contribute to fuel...even having our lights on does the same although very minor but wev had to activate these (radio/lights).
Activating the Aircon uses fuel.....under/over inflated tyres uses fuel....so im guessing activating the cruise surely must also use a bit of fuel if activated.
personally i think cruise is a waste
Activating the Aircon uses fuel.....under/over inflated tyres uses fuel....so im guessing activating the cruise surely must also use a bit of fuel if activated.
personally i think cruise is a waste
Last edited:
cruise at 70 mph will use hte same fuel as driving at 70 otherwise. cruise is not like aircon, it doesnt need any compressors running or anything.
sgb27
Guest
Everything in the car that uses power will reduce your mpg, but you need to be realistic. Your engine is generating about 10000 W of power to keep you at a constant 60 mph, so a set of lights using 100 W is going to make about 1% difference.
When travelling at a constant speed (eg on motorways) slower always uses less fuel. You must average your mpg over a long distance though, even very slight inclines or wind can affect the numbers by a large amount. Also the fuel your engine needs to develop to keep a constant speed is roughly proportional to your speed squared, so 85 mph is going to need twice as much fuel as 60 mph, and 95 is going to need twice as much as 65.
Off the motorway the speeds are lower so don't make so much difference, the most important thing becomes how often you brake. Braking simply wastes fuel, it's far better to lift off the accelerator 300 metres from a corner rather than braking 50 metres from it - it uses 250 metres less of fuel just for that one corner alone. Leave a bigger gap to the car in front and try to anticipate thing further in advance to avoid having to brake except when only absolutely necessary.
Lower RPM doesn't automatically equal less fuel being used, the efficiency of the engine depends on both RPM and torque (throttle position) in a non-trivial relationship (I have a chart from a petrol engine if anyone is interested). The 6th gear ratio will have been chosen to put the engine at the most economical operating point at 130 km/hr (or whatever speed they think will be most common).
When travelling at a constant speed (eg on motorways) slower always uses less fuel. You must average your mpg over a long distance though, even very slight inclines or wind can affect the numbers by a large amount. Also the fuel your engine needs to develop to keep a constant speed is roughly proportional to your speed squared, so 85 mph is going to need twice as much fuel as 60 mph, and 95 is going to need twice as much as 65.
Off the motorway the speeds are lower so don't make so much difference, the most important thing becomes how often you brake. Braking simply wastes fuel, it's far better to lift off the accelerator 300 metres from a corner rather than braking 50 metres from it - it uses 250 metres less of fuel just for that one corner alone. Leave a bigger gap to the car in front and try to anticipate thing further in advance to avoid having to brake except when only absolutely necessary.
Lower RPM doesn't automatically equal less fuel being used, the efficiency of the engine depends on both RPM and torque (throttle position) in a non-trivial relationship (I have a chart from a petrol engine if anyone is interested). The 6th gear ratio will have been chosen to put the engine at the most economical operating point at 130 km/hr (or whatever speed they think will be most common).
Last edited by a moderator:
Deleted member 74601
Guest
To be fair, mpg is is **** this time of year as well.
I've seen my tank averages drop from 64/65mpg to 58/59mpg. All down to colder temperatures, wetter weather, different fuel (winter fuel has a lower freezing point) and higher winds.
I noticed a big change when I went on holiday. I filled up my car before winter fuel was introduced in November, and came back after it had been introduced. My MPG on my tank that I filled up before I went was 64.8mpg, the mpg on the first tank when I came back was around 61.5 - my lowest tank since the first two. After that it went 59, 60, 58. The tanks were I got 60 mpg and 58mpg where actually in warmer temperatures than the tank where I got 64.8mpg, all down to shitty winter fuel.
All my tanks are done with a m'way cruise speed of 70mph.
I've seen my tank averages drop from 64/65mpg to 58/59mpg. All down to colder temperatures, wetter weather, different fuel (winter fuel has a lower freezing point) and higher winds.
I noticed a big change when I went on holiday. I filled up my car before winter fuel was introduced in November, and came back after it had been introduced. My MPG on my tank that I filled up before I went was 64.8mpg, the mpg on the first tank when I came back was around 61.5 - my lowest tank since the first two. After that it went 59, 60, 58. The tanks were I got 60 mpg and 58mpg where actually in warmer temperatures than the tank where I got 64.8mpg, all down to shitty winter fuel.
All my tanks are done with a m'way cruise speed of 70mph.
Last edited by a moderator:
This always makes me laugh. This is the effect it can have... but obviously don't get that close 
http://www.youtube.com/watch?v=lnYp4srEooI
http://www.youtube.com/watch?v=lnYp4srEooI
sgb27
Guest
The thick curved black lines are constant power lines, so if you know you need eg 25 kW of power the engine must operate somewhere along the 25 kW line. Using different gear ratios will allow the engine to operate at different points along that curve. The closer you are to the max torque curve along the top means you need more throttle.
The thin black lines are iso-efficiency lines, the 245 is the best efficiency, it is measured in grams of fuel used per kWh. Note the engine speed is in rad/s not RPM.
Similar threads
