Which uses more petrol?

[corn_flakes]

starting your engine, or idling for a few minutes?

just a random thought i had after seeing someone switch off their engine at the lights today. a particular light that stays red for about 5 minutes.

so lets hear the experts and your rationale behind this...

how much petrol is used in igniting the engine?

vs

how much petrol is used while idling?

[bigjo5]

starting ur engine eats more petrol

[destrukshn]

yes starting your motor consumes a fair bit of petrol.
leaving it idle would probably be better.
lol.

[Zilli]

yes starting your motor consumes a fair bit of petrol.
leaving it idle would probably be better.
lol.

ditto

[corn_flakes]

what's the rationale behind this? :D

it's a debate, explain your answers! ;)

[bigjo5]

cause when u start up the car it pumps a fair bit of petrol in to get the engine started or moving

[Chi]

You wana save petrol, go catch a bus.

[corn_flakes]

i didn't say i want to save petrol.

i'm just asking a question since i saw someone do that today.

[blk_shadow]

it will consume alot more when your engine is cold (during starting), cos it takes some amount to heat up the muffler/exhaust to certain degree.

[corn_flakes]

^ anyone want to debate that? sounds pretty clever. lol

[Petronas]

In the "old days" when everyone had carburetors it took some extra fuel to start the engine because most everyone would automatically step on the gas pedal when starting and that would activate the accelerator pump forcing out a big shot of fuel. Today if you have a fuel injected engine and it's up to running temperature shutting off the engine is better for fuel mileage because when the engine is off you are burning NO FUEL AT ALL.

I have a dual carby... Does this mean that (If I do not step on the gas pedal when starting) I would save petrol if I let it idle for lets say 5min rather than restarting an up-to-temp car?

[quangsta]

i reckon either way the amount save would be minimal....cause the longest time u'll b sitting still in traffic is at train crossings and at the most it would be for 5mins before you have to atleast move. Having said that you wouldnt know if it was a 5 minute wait or not so you'll probably wait for the first train, realise theres another one, wait a bit more incase it would come straight away realise its not AND then shut off your engine.

by the time you decide to turn off your engine you'll save 1 minute of idling, do this everday for 5 days (assuming happens to you EVERYDAY which i hihgly doubt it would) for 48 weeks, which means 240minutes of idling. thats 4 hours which by taking a wild guess would consume 1/4 of an average tank? (assuming a tank would cost $50) $50/4 = $12.5 you would save a year.

but by turning you engine on and off whenever you can, your starter motor would be used twice as much as it could be have been used. starter motor cost approx $250 to fix?? (wild guess again) every say ~10 years. $250/10 = $25 a year. assuming it will shorten ur start motor life by 5 years $250/5 = $50

so technically you'll be spending an extra $25 a year to fix your starter motor inorder to save $12.5 in petrol. worth it?

thats my uneducated guesstimates of prices and usuage =)
if someone confirms this cool, if not then ah wells i cbf turning my engine and off all time anyway so just leave it on

[corn_flakes]

ROFL!!!!!

your uneducated guestimates are awesome!

i never shut my engine off, but have just always thought about people who do it at the lights. maybe they're running low on gas? which is ironic as people say u use more gas starting ur engines than idling. lol

[NSPYRE]

quangsta, going by that rationale, u could say that idling ur car for long periods is not good for your car. when idling, the engine is not working at its peak operating temperature so fuel doesn't undergo complete combustion. this means that fuel residues are left and they can contaminate engine oil and damage engine parts. water can also condense in the vehicle's exhaust which can lead to corrosion and reduce the life of the exhaust system.

an idling engine releases twice as many exhaust fumes as a vehicle in motion, polluting our air for no good reason. now, can u really put a price on the quality of our air, or for that matter, our lives? :P