|
I know that the consumption readouts from on-board computers are not necessarily that accurate but I would have expected that cold weather and low temperatures would have improved my indicated fuel consumption. The fact is that, regularly driving the same 15 mile route in the same manner, my fuel consumption has worsened by about 5 mpg indicated. Any ideas please? The figures are still accpetable but I would have thought that cold weather would have improved the engine's overall efficiency but this does not seem to be the case!
|
|
It is the opposite.The warmer the air temp the better the mpg/factors include moisture make up of the warm air/oxygen content etc.The colder the air temp is the longer it takes for engine to reach normal operating temp.
|
|
|
|
I agree with your findings. I achieved typically 37 mpg in the summer, but 32 mpg in the winter (calculated from the distance I travel between fill-ups and the amount of petrol required to fill the tank). I believe this is because the fuel/air mixture is richer when the engine/air is cold.
|
|
Mech1 thanks for that. I was working on the knowledge that a jet engine works better when it is given cold air to use ie a better density of air and I though that the same would apply to a car engine. Certainly what I have observed bears out what you say.
|
It's true that the engine is more efficient with cold air coming in, unfortunatly, this is more than cancelled out by the richer mixture required to reach normal operating temp, and during warmup, the cold block is sapping energy up like a big heat sink, energy which should be going on propulsion.
Cold air intake is good, that's why air intakes should take air from a cold place like the grille, and not from within the hot engine compartment, hence the intake piping to the front. It;s also why many of these 'sporty' air filters which do away with the trunking are useles, as they take hot air in. These filters are designed for the race car with custom made intakes.
|
|
That isn`t the case.The air intake is taken from front of car to enable the engine to get the air needed for combustion as you know it`s a scavenger ie air is pulled in by the piston the ram air effect helps the induction to get the air needed.as the air heats up during it`s flow to manifold/bores makes it even faster for the fuel to explode.hence the better fuel economy less fuel needed to operate the engine.
|
|
|
|
|
I don't know how constant the temperature of underground fuel tanks is from summer to winter, but assuming the fuel is a few degrees colder, each litre you buy in winter should contain marginally more carbon (=energy) because of higher density. So your engine's consumption may rise a bit more than you think.
|
|
|
|
|
I'd guess my figures (from actual consumption & mileage) show the same seasonal variation as yours
and as well as the 'climatic' factors, bear in mind there is more school traffic on the road (no 'its a nice day, you can walk'), and also dark/wet/icy conditions mean there are probably more accidents to slow traffic down, and there is (chip on shoulder mode) a large percentage of the population who don't know how to drive, whose only response to dark/wet/ice is to go slower and brake harder, neither of which will do your fuel efficiency much good!
--
Bora - what Bora ?
|
I'm one of those sad gits who has kept a record of fuel/mpg since 1980. In every case, including diesels, mpg has dipped in the winter months, typically 3 mpg or so . I really must get out more in 2004!
Baz
|
|
|
|
Speed hump`s aren`t any better!
|
|
My Octavia 1.4 does 46 mpg in the summer and 41 mpg in the winter, I just put it down to the time the engine runs whilst defrosting the windows and slightly worse winter traffic queues.
|
|
|
|
|
My 230E auto Mercedes does about 22 in winter and about 24-25 in urban London in summer. Don't forget in winter...
1.Grease in bearings and oil is thicker so more drag/friction
2. Engine/transmission is cold and tighter so more friction
3. Heated window and lights put a load on the engine
4. Tyres are cold and flex less = uses more energy.
5. Denser cold air is harder to part = drag
|
|
|
Yes, I've always found Miles/gall dip in winter. Longer warm up times, combined with more drag even when warm as the transmission temperature will drop slightly - it's not thermostatically conrolled like the engine. In addition. there's more drag from cold wheel bearings, more use of the electrics - lights, HRW, heater fan etc - which requires more power to the alternator. All these factors offset the slight increase in air mass throughput of the engine.
Regards
John S
|
|
don't forget more wind - car has to push more - and dirtier/rainy roads - more resistance to the tyres. Mind you, post on cold performance explains how my Corolla goes better when its cold......
|
I would like to suggest something relevant to 'Summer/Winter' MPG.
Petrol and Diesel both have a 'Summer' and 'Winter' spec,(for instance up to 25% jet fuel in 'Winter' blend diesel to reduce waxing).
|
Petrol and Diesel both have a 'Summer' and 'Winter' spec
Totally irrelevant to the subject, but I understand that "margarines" have a different blend in winter.
--
L'escargot by name, but not by nature.
|
Totally irrelevant to the subject, but I understand that "margarines" have a different blend in winter.........
So if the different components added to winter blends are lighter fraction and have lower calorific values ...this is going to affect the fuel consumption isn't it? ....or am I missing something?
|
|
Yes, winter fuel is lower in calorific value, petrol has butane infused into it, to help cold starting. But when cold, it also becomes more dense anyway. During the hot summer, customers often complain to the fuel companies after thay have had a delivery of gasoline andt it is 600 litres short or something, but the oil company just tells them that their tanks are in the sun and the retailer's below ground and it is due to the temperature, and there is nothing they can do.
|
|
I may be corrected here but butane is compressed gas it cannot be contained in petrol on pressure release it turns into it`s original state gas.Besides which when filling up you would destroy filling station.slightest spark/as I say could be wrong
|
Well, I thought that too. It was by someone who worked for ESSO. Maybe it dissolves in the liquids, like CO2 and O2 do in water?
If you smell it in winter, it does have an LPG whiff to it.
|
|
Propane won`t dissolve it only decompresses to be a gas that heats when ignited ie gas cooking/heating.same as used in caravans I believe it is used on running cars but as a main fuel the 2 cannot be mixed
|
|
|
|
Butane boils at about 0°C, and it will happily mix with all its close relatives like octane. Most modern cars have sealed recirculating fuel systems, so once the stuff is in the tank and the cap is put back it should stay there, unless external temperature rises a lot when some will vent I suppose.
|
|
no such a sealed fuel system.Ie fuel evaporate`s the system only allows the unused fuel to return to the tank.the excess fuel vapour exit`s the pipe on top of tank/or through the filling cap unless anyone knows better.I think we are straying from first post.have a good Christmas all nice talking
|
|
|
|
