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A couple of questions...
1. My petrol consumption seems to have risen, I used to squeeze 320 miles out of a tank, now it's 260-280. This has happened since the weather got cold, is this the reason? My car is almost nine years of age, could it be general elderlyness? Any other reasons?
2. I seem to remember reading somewhere a long time ago that while the heat from the heaters was free because it came from the engine which was hot anyway, the rear windscreen demister was powered differently and so actually cost money each time it was on. Is there any truth in that?
Thanks!
2. I seem to remember reading somewhere a long time ago that while the heat from the heaters was free because it came from the engine which was hot anyway, the rear windscreen demister was powered differently and so actually cost money each time it was on. Is there any truth in that?
Thanks!
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Im not sure about the heater as they run off the battery! and the alternator charges the battery!
Are your tyres at the correct pressure as this has an affect on fuel consumption.
are you using air con? as this puts extra strain on the engine which in turn also uses more fuel.0 -
1. Engines run more efficiently with cold air, so no it's not the reason. Have you had it serviced regularly (spark plugs, air filter etc) and what are the tyres and wheel alignment like? Unless you've done starship mileage or the engine is knackered there's no reason why you should notice a discernable drop in economy IMHO. I had a 16 year old BMW that happily retuned 30mpg until the day I sold it after 9 years of ownership. Have you changed fuel provider/type? My current car runs more efficiently on super unleaded than standard because it alters the timing to take advantage of the higher octane.
2. Provided you're not using climate control but rather a normal vent, then hot air from the vents is achieved using heat generated by the engine. But until the engine reaches normal operating temperature you are asking the it to do more work by having the heater on. As for the rear de-mister, yes that will put a load on the system.0 -
joshm wrote:As for the rear de-mister, yes that will put a load on the system.
In what way? Is it harder for the battery to work?
I don't have aircon.
The spark plugs were done a year/12k ago, as was the air filter. The oil was done about four or five months ago. I think the air filter does need changing/cleaning, doesn't it.
I will check my tyres, I've been meaning to do that for a few weeks. In fact, i will do it tomorrow as I've just finished work for Xmas!0 -
waterbaby wrote:In what way? Is it harder for the battery to work?
I don't have aircon.
The spark plugs were done a year/12k ago, as was the air filter. The oil was done about four or five months ago. I think the air filter does need changing/cleaning, doesn't it.
I will check my tyres, I've been meaning to do that for a few weeks. In fact, i will do it tomorrow as I've just finished work for Xmas!
The extra power needed for the heating elements places an extra strain on the engine - to test this, whilst the car is idling, switch on the rear heater and listen to the noise of the engine, same with the heater fan - you'd be surprised how much the fan uses!
Spark plugs should be done every 12 months though if you aren't doing high mileage then don't worry about it too much. The air filter depends how black it is but generally this would increase efficiency - I got mine from the dealer for £16 and installed it myself, not paying their outrageous labour time of 45 mins :rolleyes:
Tyres - take it to a garage somewhere and have them check the alignment, wheel balance, tracking and ask to check if the tyres are wearing evenly. Don't agree to any work - some places will pounce if they sense you aren't versed in this type of stuff. Any more questions just ask
and maybe someone who knows a lot more than I do 
will reply :T 0 -
Car engines are most efficient with warm air flowing into them, not cold. This would not account for all of the change. Have you changed where you are buying your fuel?0
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not true, cold air is more dense than hot. cold dense air as the affect of increasing the compression slightly. intercoolers are fitted to super charged engines to cool the incoming air.reduceditem wrote:Car engines are most efficient with warm air flowing into them, not cold. This would not account for all of the change. Have you changed where you are buying your fuel?0 -
Well I've just checked my tyres and they could do with about four units each (is that psi or bars or something), anyway I know how to fix it and I will do so before I venture out in the chiliness again!
Bit annoyed to have let that slip, I usually check them often as I know it affects safety.
So I'll see what effect that has.
And the issue of the air temperature, well there isn't much I can do about that anyway I guess
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reduceditem wrote:Car engines are most efficient with warm air flowing into them, not cold.
Sorry, but I disagree. Can you substantiate that claim as I'm convinced that a cold air intake increases the efficiency of an engine versus warm/hot air.albertross wrote:Also, any form of heating uses extra fuel, it is not a free byproduct.
Not sure I fully agree with this either. Once the car has reached operating temperatures, the thermostat opens and the coolant starts pumping around the enigne to draw heat away (it is dispersed by the radiator). So losing heat by this method is no worse than opening your vent. Granted, if you switch your fan on or the car has not warmed up sufficiently you're using extra energy, but otherwise you're just diverting heat that would otherwise be lost via the cooling system...
If you can design an engine that doesn't produce any excess heat and runs efficiently you'll be a very rich man!0 -
You could try using a thinner oil in your engine, one of the reasons a car uses more fuel in winter is the oil doesn't 'thin' as much as in summer and causes more 'drag' on the moving parts in the engine.
Even though an engine is more efficient with cold air going in, it will use more petrol. Cold air is denser than warm, that means the air mass (or weight) is greater and with that extra air there has to be extra fuel as well to compensate. But your car should perform better in cold weather, so enjoy it 0 -
Crabman wrote:The air filter depends how black it is but generally this would increase efficiency - I got mine from the dealer for £16 and installed it myself, not paying their outrageous labour time of 45 mins
Yes that is a bit mental, I have done a little bit of car maintenance at an evening class and I have taken out and refitted my air filter, no way does it take 45 mins! More like 5 if I remember correctly.
I changed my own brake discs and pads in the summer, that cost me £45 instead of £125 at the garage. It did take me 5 hours, but I can see that for a skilled person it would not take long at all. (Don't worry, I was overseen by someone who is fully competent!)0
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