Any ideas for some petrol/diesel cars?
What if you want to sit in the car with the air coin on a hot day?
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The fairly obvious answer is zero mpg. However I'm sure this is not what you're looking for....
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Diesels will generally consume less fuel per unit of time than similar sized petrols, and using the aircon will increase the rate of usage of the fuel.
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I had a 1.4 Civic yesterday - when idling with the aircon on, the MPG meter was showing around 90.
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It always used to be said that a traditional diesel engine used a tiny amount of fuel at idling because direct injection meant that every drop of fuel was actually used. For that reason commercial users and boat owners would let the engines idle for long periods.
I even heard it said on good authority that the railways' big Deltics etc were left running non-stop.
The argument with petrol engines was that carburettors or indirect injection lost a certain amount of the fuel in the inlet manifold, which then had to be sucked into the combustion chamber rather inefficiently.
But the designs have all changed now, so perhaps neither of these extremes now apply.
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>>I even heard it said on good authority that the railways' big Deltics etc were left running non-stop.
This is still true of HSTs - among the reasons for doing this is that when left for a long period of time, the engines were susceptible to coolant leaks into the manifold. A cylinder would fill, and hydraulic upon starting!
This extensive idling of HSTs used to be a problem for me and SWMBO, because our house was only a couple of hundred yards from the depot in Derby, and on a summer's evening, the noise and fumes were a tad annoying.
With the arrival of Number_Nipper, we felt the magnetic pull of the suburbs, and now we live on the outskirts of town - the evening symphony of large V12 diesels is no more an issue.
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Then Andy you must have been moving? Because if you were stopped and the engine was on then you are doing 0 miles (per gallon) since you are stopped. Either that or there is a software glitch in the meter.
Stationary engines measure their fuel consumption in gallons (or litres) per hour.
Edited by Billy Whizz on 15/05/2008 at 09:56
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The real time fuel consumption computers on my various Vauxhalls have all shown around 0.2 - 0.3 gallons per hour when idling stationary. That's always seemed quite low to me but I've never run one dry to see how accurate it really is.
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At 0.3 gallons per hour, I make that £1.70 an hour at current diesel rates (1.25/l), so about 3 pence per minute.
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And a Tap on the Door by a keen officer to tell you you are in violation of the road traffic act for "Excessive Idling". Regards Peter
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Those figures are for a warm engine, at cold start up the figure is about 1.2 gal/hour and drops fairly rapidly over the first few minutes to the warm figure. On SWMBO's Zafira switching the aircon on changes the display from 0.2 to 0.3, maybe the aircon is adding 50% to idle fuel consumption, maybe it's just the way the computer rounds the figures up or down.
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Of course the car wasn't moving - the figure is the theoretical distance the car would travel were it possible to move. I guess that switching the display from mpg to gph wasn't worth the effort and most people wouldn't notice if you did.
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AndyP, that is impossible. mpg is miles per gallon, if there are no miles, then the value for mpg is 0, as for every gallon you have burned you have moved 0 miles, not 90. I wouldn't trust a computer that had been so badly programmed!
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My Vectra-C displays fuel consumption in gallons per hour when the engine is idling (and below 8mph).
Usually 0.3 to 0.4 gal/hr when idling (2.2 Petrol engine)
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DD,
As a matter of interest what sort of "average" mpg do you get from you Vectra? My friend has one, 2,2 manual and is averaging 27mpg. This is with no motorway use, local rural journeys of about 10/15 miles each way. He thinks that this is a bit heavy.
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mjm, my 2.2 is an auto, and if I've got my slippers on instead of my usual heavy boots I can average 27 to 28 mpg on 'rural' journeys. More often than not it's more like 25 mpg, but it has been known to drop down to lower than 20 mpg with my lead boots on.
At a constant 50 to 60 mph, I can average around 38 to 40 mpg.
70 to 80 mph (motorway) averages 34 mpg, as does driving down to the south coast using the backroads from Oxfordshire to Dorset.
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Thanks, DD
In the minefield of estimating what any car should do to the gallon under "normal" conditions, his 27/28 to the gallon seems about right.
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I have a 1.8 Vectra, and with carpet slippers, and an indicated 70mph, I get 44mpg including some town miles.
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SWMBO has a 2.2 Vectra Estate - it's never seen 30mpg - either with her carpet slippers on shortish runs or my hobnails on long motorways!
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Doesn't excessive idling glaze the bores on diesels?
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SWMBO has a 2.2 Vectra Estate - it's never seen 30mpg - either with her carpet slippers on shortish runs or my hobnails on long motorways!
Mine saw an average of 30.5mpg over 4 years and 50k miles so no surprises there !
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I had a 1.4 Civic yesterday - when idling with the aircon on the MPG meter was showing around 90.
My VW shows the last instant mpg when coming to a stop so could show as low as 18 mpg and high as 200mpg.
When stopped in traffic I switch to the average mpg and then see that reducing.
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