club.liberty.asn.au

Okay, so I know you use more petrol when you have the air con on, but how much more?

Im currently on 10L/100km, how much would it go up to if I ran the air con all the time lol...?

Also, how much more petrol does cruise control use, or is this a myth?

Depend on circumstance. In city driving studies have shown that air con can add 5% to the average fuel use. So in the city, windows down! On the open road it can be the opposite - the additional drag created by open windows can increase fuel use by more than air con compressor, so windows up, air con on.

Cruise control is not as economical as a human because it cannot anticipate the undulations in the road. If you can increase your speed leading up to a hill and then use less throttle as you climb the rise, this will be more economical than the cruise control which waits for a certain decrease in your speed before increasing the throttle setting - thus trying to increase speed when nature is working against you ... so no myth there!

Mythbusters tested this (Yes I watch Mythbusters haha) Windows down uses more fuel then air conditioning.
Ive gotten into the habit of turning my air con off in my car a few streets away from home, about 5-10 minutes worth of driving.
the car stays cool and I dont waste the fuel. Just a habit Ive picked up from my tight arse father. hahah.

tmacca wrote:Depend on circumstance. In city driving studies have shown that air con can add 5% to the average fuel use. So in the city, windows down! On the open road it can be the opposite - the additional drag created by open windows can increase fuel use by more than air con compressor, so windows up, air con on.

+1 If in bumper to bumper traffic I go windows down if I can bear it, also due to the car suffering from some decent heatsoak if in bumper to bumper and it's a hot day since the aircon condenser reduces the cooling effect of the radiator.

When driving up to Shepparton I had aircon on and windows closed the whole way and still got 7.5L/100Kms.

Yeh just found this on the web

REVISITED: Running a car with air conditioning on is more fuel efficient than running with the windows down. (From Episode 22)
PARTLY CONFIRMED
The fundamental flaw in the MythBusters’ test was that the point where the drag becomes powerful enough to inhibit a car’s performance with windows down was inside their 45 – 55mph margin at 50mph. Going less than 50mph it is more efficient to leave your windows down, but going greater than 50mph it is more efficient to use your A/C.

SO pretty much if ur going 80km or faster, air con!

The Lib is 3 years old and 100000k and I can t remember
turning the AC off Wish I could super glue the "S" drive to
S#

BUDDAH wrote:The Lib is 3 years old and 100000k and I can t remember
turning the AC off Wish I could super glue the "S" drive to
S#

Same here, owned the car just short of 2 years (50,000k's) and think I may have turned the AC off maybe once? For the sake of a few cents worth of fuel I'd rather be comfortable all the time.

Kevlar GT wrote:

BUDDAH wrote:The Lib is 3 years old and 100000k and I can t remember
turning the AC off Wish I could super glue the "S" drive to
S#

Same here, owned the car just short of 2 years (50,000k's) and think I may have turned the AC off maybe once? For the sake of a few cents worth of fuel I'd rather be comfortable all the time.

Thats what im trying to figure out, how much of a full tank would the AC use? $2 or something lol?

Laps wrote:Thats what im trying to figure out, how much of a full tank would the AC use? $2 or something lol?

The only person who can work that out is you, we don't know how good or bad a driver you are so next time you fill up turn on the a/c and do your own test. Let us know how you get on!

Bob.

The air-con shouldn't use much more if your going for a highway cruise. But it will (From experience) still reduce your overall mileage per tank.

Obviously this varies from car to car... In a V8 I've found it's made a negligible difference but in a small 4 banger it can make a massive one... Aside from the fact it will zap a lot of power

Cruise control shouldn't use any extra fuel, in fact it should make you use less as the computer only applies enough throttle to keep the car at the set speed. Whereas if you are controlling it, you'll find you stab the throttle from time to time because you've dropped too much speed etc etc etc.

Well, funny you guys should mention this!

I've started running recently with the aircon on a LOT (probably due to the week of 34+ temps in Melb) and my fuel econo has jumped up by ~.8-1l/100km This is all heavy peak hour or shot trip stuff when it's a combo of cold start and heavy aircon to cool the car.

Didn't expect that much difference, but there ya go.

Modern cruise control saves you fuel!

Detroit Diesel Series-60 engines with DDEC controls are programmed to give an extra 25kW when cruise is turned on, but it still delivers a lower fuel consumption. It's not like it used to be when the car put down too much power, then dropped it, too much, then gives a bit extra to make it up, but too much and back off etc... Now DBW technology is intelligent and responds sensibly to demands.

I was always told <80km/h windows down but above it's air con, but like most I quite frankly couldn't care less about the $5 fuel difference and leave it on all the time. It gets too uncomfortable with the leather if you don't. However, it does occasionally recieve a tap of the 'off' button when I'm blowing away some fake evo or LoganMobile 200SX/VK Bombadore...

GT-B

I guess what it comes down to is this one question:

Are you a Prius person?

Golf Tango - Bravo wrote:Modern cruise control saves you fuel!

Detroit Diesel Series-60 engines with DDEC controls are programmed to give an extra 25kW when cruise is turned on, but it still delivers a lower fuel consumption. It's not like it used to be when the car put down too much power, then dropped it, too much, then gives a bit extra to make it up, but too much and back off etc... Now DBW technology is intelligent and responds sensibly to demands.

I was always told <80km/h windows down but above it's air con, but like most I quite frankly couldn't care less about the $5 fuel difference and leave it on all the time. It gets too uncomfortable with the leather if you don't. However, it does occasionally recieve a tap of the 'off' button when I'm blowing away some fake evo or LoganMobile 200SX/VK Bombadore...

GT-B

I don't know about your Detroit example but in our vehicles cruise definitley uses more than an astute driver would and its for the reasons listed above that the ecu cannot anticipate and will alays try and keep a fixed speed at all costs. Whereas the smart driver will allow slight slowing on uphill grades to negate having to floor the throttle. Also the ecu will only increase throttle after the car has already begun to slow
And there is a small amount of 'catchup' for the engine to do.

As for aircon economy I can tell you the IDC increases from 1.3% at idle to 1.6% with the ac switched on so around a 15% increase in fuel useage at idle. As for increase in usage whilst driving well that depends on how you drive. But arbitrarily around 5-8% is fair

Kevlar GT wrote:I guess what it comes down to is this one question:

Are you a Prius person?

Nope

I ADD to the greenhouse effect with my aircon on if >30 ambient