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Fuel Consumption.

Started by The Saint. (Owen), December 17, 2017, 22:01:48 pm

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The Saint. (Owen)

I have recently bought my first diesel powered car and my question is (or should be) quite simple.
Does a diesel engine use more fuel when cold or doing short journeys of about 3 or four miles like a petrol engine would?

[answers on a postcard to the usual address please.]   ;) ;)
Electrickery is the work of the devil.
Proper aeroplanes are powered by engines.

meharibear

Inside every old person is a young person wondering what happened.  (Terry Pratchett)

paulinfrance

If you do trips of less than 10 kilometres you diesel wont last long, :embarassed:
and it will also use at least 30% more diesel it takes much longer to
warm up than a petrol engine,  you should have bought a petrol engine,,,  :-X
Mode 2 THE only way to fly

FrankS

Quote from: paulinfrance on December 18, 2017, 08:00:56 am
If you do trips of less than 10 kilometres you diesel wont last long, :embarassed:
and it will also use at least 30% more diesel it takes much longer to
warm up than a petrol engine,  you should have bought a petrol engine,,,  :-X


Why does a diesel take longer to warm up?

British Victory

December 18, 2017, 08:20:12 am #4 Last Edit: December 18, 2017, 08:22:24 am by British Victory
Quote from: paulinfrance on December 18, 2017, 08:00:56 am
If you do trips of less than 10 kilometres you diesel wont last long, :embarassed:
and it will also use at least 30% more diesel it takes much longer to
warm up than a petrol engine,  you should have bought a petrol engine,,,  :-X

I wonder why most medium sized transit types are diesel oh and london cabs.
Diesels, modern ones at least, are slow to warm up because they burn less fuel. It's petrol ones that suffer with many short journeys, the richer mixture helping to break down the cylinder lubrication.
I would agree that the item most at risk is the diesel particulate filter, even this can be maintained by regularly following the manufacturer's instruction manual.
However VAG blew it all into the water with their con job of several years ago.
My ancient series 2a landrover diesel used to tow my 2 tons of boat and trailer 5 miles to the launching ramp and 5 miles back again every weekend and it didn't suffer.
there's only one f in RCMF,
               John

paulinfrance

Your LR is an ancient diesel with direct injection, as for wear diesel lubricates the cylinders so it should do a good 250.000 miles or even the double, but it will coke up the valves and exhaust, and cold the consumption will be 50% when cold especially when towing.

Todays diesels are different, and as you say the exhausts often make the engine go into 'safe mode' limiting the
speed to 50 mph, and the turbo's clog up and seize !
Diesel 'burns and has a cooler running temperature and as the compression ratio is more than a petrol engine it is heavier so two good reasons why they take so long to get to their optimum running temperature,  Petrol engines 'explode' with lower pressures so they are built lighter so they warm up faster, and are also higher revving, my Peugeot ( 2 litre HDI diesel ) takes 8 klms to warm up my petrol Jag, 2 klm's !.
Mode 2 THE only way to fly

itsme

even this weather (-1) my two litre diesel Mondeo warms up in 2k. Sallys diesel Corsa takes 8....

paulinfrance

Quote from: itsme on December 18, 2017, 12:16:05 pm
even this weather (-1) my two litre diesel Mondeo warms up in 2k. Sallys diesel Corsa takes 8....


Yes it just proves what crap Fords are,,,  :''
Mode 2 THE only way to fly

FrankS

My 2 litre BMW 520D warms up very quickly, and doesn't seem any longer than our 1.1 petrol Mitsubishi petrol Colt, based on heater output as the Colt doesn't have a temperature gauge.

BTW the compression in diesel engine takes the temp up to around 600-700 C before the diesel is injected, where as the post combustion temp in a petrol engine is around 700 C. But a petrol engine has to regulate the air and fuel to around 14:1 for it to burn whereas a diesel doesn't and at low power the ratio could be as high as 160:1. One of the reasons for high NOx in diesel engines is the higher combustion temp. http://clean-carbonenergy.com/nox-emissions.html

itsme

Quote from: paulinfrance on December 18, 2017, 13:21:21 pm
Yes it just proves what crap Fords are,,,  :''
yep. Wont have a word said against it. Loads of room (estate) and plenty of power to pull the caravan.

paulinfrance

Quote from: itsme on December 18, 2017, 15:58:22 pm
yep. Wont have a word said against it. Loads of room (estate) and plenty of power to pull the caravan.


OMG do you wear lycra and ride bikes as well ?,  :banghead:
Mode 2 THE only way to fly

itsme

Quote from: paulinfrance on December 18, 2017, 17:07:03 pm
OMG do you wear lycra and ride bikes as well ?,  :banghead:
How dare you. There are insults and there are insults...

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paulinfrance

Quote from: itsme on December 18, 2017, 17:13:41 pm
How dare you. There are insults and there are insults...

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I could except a caravan OR a cyclist but not both  ;D
Mode 2 THE only way to fly

itsme

Quote from: paulinfrance on December 18, 2017, 18:25:36 pm
I could except a caravan OR a cyclist but not both  ;D
Not ridden a bike in years. Caravan is mostly for model shows and fly ins. Estate car can get at least two quarter scale models in. And I carry a third of the gear for my band. No room for bikes. .....

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FrankS

Quote from: paulinfrance on December 18, 2017, 13:21:21 pm
Yes it just proves what crap Fords are,,,  :''


Says the man whos Peugeot takes forever to warm up  :''

keithl

A key thing about diesels and short journeys is the Diesel Particulate Filter - most diesels in the last 8-10 years have one fitted.  These reduce the nasty emissions that the government conveniently forgot about when setting the regulations and taxes based on CO2.

The problem with DPFs is that they clog up.

When the engine is hot, and you pass 50mph they start a cycle that burns off the particulates.  This takes between 6 and 10 miles.  If your speed drops below 50mph during that time, the cycle does not complete.  This causes two problems, the much from the partial clean is dumped into the sump and secondly it hasn't made any difference to the state of the DPF so it needs to do it again.

If your usage is mostly short journeys, then get in the habit of doing a run at least once a month or you will end up with a £300 garage bill to unclog it.

I'm not sure if the newer diesels with "Adblue" still have this problem?
Warning: objects in the mirror may be close than they appear (or I'm creeping up on you from behind)

itsme

well seeing as I am surrounded by 50mph speed cameras for ten miles that is a bit of a problem. So i need to get on to the motorway and do a pointless journey of ten miles once a month? (Hoping for no holdups) Thanks DVLA.

paulinfrance

Quote from: itsme on December 19, 2017, 10:51:35 am
well seeing as I am surrounded by 50mph speed cameras for ten miles that is a bit of a problem. So i need to get on to the motorway and do a pointless journey of ten miles once a month? (Hoping for no holdups) Thanks DVLA.


No just drive around like my wife does, all in 1st gear,,,  :co
Mode 2 THE only way to fly

Bad Raven

Quote from: paulinfrance on December 19, 2017, 11:23:15 am
No just drive around like my wife does, all in 1st gear,,,  :co


Now, most people would take that as a joke, but I had to do a couple of long distance journeys in a mini-bus sharing with someone who apparently thought that a gearbox had to be used sequentially every time, so they went down to first on the move at far too high a speed every time in traffic (only sometimes recognising that they could not let the clutch fully grip), before coming back up the gears one at a time till they found one that wasn't banging the valves against the pistons.

They had NO concept of which gear was the right one for the conditions. It says a LOT for Ford Transits that both the engine and gearbox survived this horrendous abuse. (Though I'm not sure my nerves ever recovered).

The various diesel (of course) Transits I drove seemed to warm up extremely  quickly, even when being driven "properly".

My TDCI Focus seemed to warm up quickly.  My current car, 2009 Octavia Estate with the Golf GTI common rail diesel, seems to take a long time if you believe the gauge, but hasn't shown any signs of disliking its treatment over the 85k its done, which for the past two years has included more short less than 3 mile journeys than previously, although it gets a 50 plus each way round trip about once a fortnight. Fuel consumption is usually close to 50mpg, and while I don't speed, I do use its acceleration and do not deliberately drive to save fuel.
The user formerly know as Bravedan........... Well if Prince can do it....................

paulinfrance

Working as a boat mechanic in the 80's, I got called out by the Mercury Z drive specialists on an
on-going problem with one of their Z drive powered speed boats, the owners drove out of the port,
across the bay ( flat out ) then down the canals all day and back across the bay where the engine
lost all of it's power then into the port, if ( maybe they did ) they had asked the owner what he was doing with
the boat they would have realised that the turbo was coking up,, a twist with a 10mm tube spanner, and
just tell them to rev it up now and again solved the problem. :study:
Mode 2 THE only way to fly

itsme

Quote from: Bad Raven on December 26, 2017, 07:59:49 am
Now, most people would take that as a joke, but I had to do a couple of long distance journeys in a mini-bus sharing with someone who apparently thought that a gearbox had to be used sequentially every time, so they went down to first on the move at far too high a speed every time in traffic (only sometimes recognising that they could not let the clutch fully grip), before coming back up the gears one at a time till they found one that wasn't banging the valves against the pistons.

They had NO concept of which gear was the right one for the conditions. It says a LOT for Ford Transits that both the engine and gearbox survived this horrendous abuse. (Though I'm not sure my nerves ever recovered).

The various diesel (of course) Transits I drove seemed to warm up extremely  quickly, even when being driven "properly".

My TDCI Focus seemed to warm up quickly.  My current car, 2009 Octavia Estate with the Golf GTI common rail diesel, seems to take a long time if you believe the gauge, but hasn't shown any signs of disliking its treatment over the 85k its done, which for the past two years has included more short less than 3 mile journeys than previously, although it gets a 50 plus each way round trip about once a fortnight. Fuel consumption is usually close to 50mpg, and while I don't speed, I do use its acceleration and do not deliberately drive to save fuel.
My Transit was always quickly up to temp. and my diesel Mondeo is excellent. Wifes Corsa (also diesel) on the exact same journey takes twice as far to warm up, and ten miles to get really hot.

paulinfrance

Older women du take longer to 'warm up',,  ^-^
Mode 2 THE only way to fly

itsme

Quote from: paulinfrance on December 26, 2017, 11:22:38 am
Older women du take longer to 'warm up',,  ^-^
Rubbish. Ask me how I know....as for the cars,  they are both the same age.

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Engine Doctor

Quote from: meharibear on December 17, 2017, 22:32:26 pm
Yes, but not so badly.

Yes they do use slightly more fuel when cold but nowhere near as much as a petrol engine .
Re short journeys ;If your car has a DPF (diesel particulate filter )you may find doing loads of short journeys will cause the DPF to bclog up. I have been mixing Two stroke o0il adde to fuel at a ratio of 200 ; 1 and had no problems  as it burns the particles . Other benefits are smoother quieter engine better pick up and better protection of the low and high pressure pumps . Oil must be normal mineral based oil , low ash self mix. NOT synthetic .
Take off's are optional ,landings are not !

FrankS

Quote from: Engine Doctor on January 25, 2018, 11:09:03 am
Yes they do use slightly more fuel when cold but nowhere near as much as a petrol engine .
Re short journeys ;If your car has a DPF (diesel particulate filter )you may find doing loads of short journeys will cause the DPF to bclog up. I have been mixing Two stroke o0il adde to fuel at a ratio of 200 ; 1 and had no problems  as it burns the particles . Other benefits are smoother quieter engine better pick up and better protection of the low and high pressure pumps . Oil must be normal mineral based oil , low ash self mix. NOT synthetic .


mmm, this technical review http://www.fuelexpert.co.za/2-stroke-oil-in-diesel-technical-study.php doesn't recommend adding two stroke oil to diesel. If it stopped the DPF from blocking up you think the manufacturers would sell it as an additive, or maybe they don't so they can sell DPF regeneration services or replacments  :''

British Victory

Don't use 2 stroke oil, much better to use first pressing of cobra, fixes everything  :ev. In a pinch you can use extract of adder, it isn't as potent as the cobra though  :af.
there's only one f in RCMF,
               John

itsme

Quote from: British Victory on January 25, 2018, 20:57:13 pm
Don't use 2 stroke oil, much better to use first pressing of cobra, fixes everything  :ev. In a pinch you can use extract of adder, it isn't as potent as the cobra though  :af.
Whatever happened to Redex?

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Bad Raven

The user formerly know as Bravedan........... Well if Prince can do it....................

itsme

Quote from: Bad Raven on January 25, 2018, 21:50:58 pm

Nothing................     https://www.holtsauto.com/redex/
It used to be a 'penny a shot' in garage forecourts.

Gaspin

Thank you "itsme" for making me really feel my years, your post reminded me of flirting with the petrol pump attendant ( yes a girl) to get a free squirt of redox in my Ford Pop.  :''

itsme

Quote from: Gaspin on January 29, 2018, 07:58:52 am
Thank you "itsme" for making me really feel my years, your post reminded me of flirting with the petrol pump attendant ( yes a girl) to get a free squirt of redox in my Ford Pop.  :''
as long as it wasnt reciprocal  ........