Author Topic: 29 mpg in 100% urban environment. Is this normal or what should I check?  (Read 2136 times)

J@zzy

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Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
« Reply #15 on: December 24, 2017, 02:18:00 PM »
Is there any way to improve mpg in winter time?

culzean

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Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
« Reply #16 on: December 24, 2017, 02:36:28 PM »
Is there any way to improve mpg in winter time?

The only way to use less fuel in winter is not to drive so much (technically this is not improving mpg because no miles / travel involved) .

To allow engine to warm up faster drive off as soon as engine is started, letting a cold engine idle on your drive means slow warm up and wasted fuel.  Using the heater can mean slower engine warm up so wear a fleece and glove and don't use heater  (like many BEV drivers do)..   Do the normal fuel saving stuff like using brakes as little as possible, change up early, don't accelerate any faster than you need to (rapid acceleration drinks fuel). Make sure tyre pressure is correct to lower rolling resistance.
« Last Edit: December 24, 2017, 02:45:22 PM by culzean »
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

Jocko

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Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
« Reply #17 on: December 24, 2017, 02:54:32 PM »
I don't put my heater on (control in the blue) until the engine warms up. This allows the blue light to go out a quarter mile earlier than if the heater control was set to red. Another thing I have been advised to do, but have never got around to trying, is to block the lower grill. Something not too permanent so it can be easily removed when the weather warms up. I have a a ScanGauge E fitted so I can actually monitor the coolant and intake air temperature.
I keep my tyre pressures 3 or 4 psi over Honda's recommended figures. I also check my tyre pressures on a weekly basis (always checking and adjusting them when cold).

madasafish

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Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
« Reply #18 on: December 24, 2017, 06:23:26 PM »
Don't accelerate hard when engine is cold.
Try not to drive up hills when engine is cold.
Brake little when engine is cold.

eagle123

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Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
« Reply #19 on: January 10, 2018, 02:52:33 PM »
Don't accelerate hard when engine is cold.
Try not to drive up hills when engine is cold.
Brake little when engine is cold.
Make sure you fill up half a tank and declutter your car take excess weight off correct oil check tyre pressure change to eco tyres drive smoothly anticipate ahead


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culzean

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Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
« Reply #20 on: January 10, 2018, 04:09:50 PM »

Make sure you fill up half a tank


With the Jazz weighing 1100 Kg saving weight of half a tank of fuel (less than 20kg) is hardly going to make any measurable difference,  in any case I try never to let my tank get less than half empty because without fuel a car is just an expensive ornament. 

A fast warmup and avoiding using brakes,  avoiding excessive acceleration and speed above 50 if possible will give best payback.

Most engines do less than 20mpg until they warm up, and with short journeys your car never gets warm.  Suggest you zero the trip and take it for a decent run (more than 20 to 30 miles) driving carefully and see how the consumption goes.  It is important to zero the trip (I do it every time I fill up) because the mpg indication is at its most accurate and sensitive when trip at zero,  as the miles build up on trip it gets very sluggish to change and after about 100 miles mpg readout hardly changes whether you are going downhill,  uphill driving carefully or not.  This effect is because the fuel usage data (the injector open time taken from ECU) is averaged out over the total miles on the trip and as the miles build up and change in instantaneous fuel usage is swamped by averaging it over more miles.   The mpg readout normally updates about every 10 seconds.


In fact if you zero the trip from cold and drive say 5 miles you will see 'cold mpg' if you then zero trip with engine warmed up you should see a marked difference in mpg.  Winter is not a good time to check MPG as the results are normally disappointing.
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

Jocko

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Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
« Reply #21 on: January 10, 2018, 06:08:33 PM »
I always fill my tank to full. Until the first click off of the pump. The only way to get an accurate mpg figure is to fill the tank, zero the trip (or note the mileage - I do both), refill tank when fuel light comes on. Divide the miles covered by the gallons added to fill tank, and there is your mpg figure.

peteo48

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Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
« Reply #22 on: January 10, 2018, 08:20:16 PM »
I do the same Jocko. Only difference is I tend to refuel when the miles left "guessometer" reaches gets down to 100. Don't like living on the edge lol (probably why I haven't bought an EV yet!)

Jocko

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Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
« Reply #23 on: January 10, 2018, 08:46:36 PM »
My dashboard display just shows Average mpg. My ScanGauge shows anything I want! If there is any likelihood of a longer run I will fill up earlier, but my local filling stations are 24 hour so if I got an urgent call in the middle of the night, I can get petrol.

John Ratsey

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Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
« Reply #24 on: January 11, 2018, 09:02:48 AM »
Short trips, particularly in the winter, are a killer for decent fuel economy. My HR-V has a trip computer display option which shows the mpg for the current trip and it's informative to watch the number increase as the journey gets longer. It takes at least 5 miles (and maybe nearer 10 miles) in the winter for the engine to warm up properly and reach full efficiency. I always knew that efficiency and economy dropped but seeing the numbers on a screen has highlighted the extent.

I've considered, but not implemented, half blocking the front grille during the winter months in order to help with the warming up. I'm surprised that manufacturers don't provide thermostatic louvres but they lack the incentive as the standard tests don't include winter fuel economy.

Jocko

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Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
« Reply #25 on: January 11, 2018, 09:40:52 AM »
I keep meaning to block the lower grill for just that very reason. It takes almost 10 miles before my average mpg starts to recover after a winter start. And the majority of my daily journeys are less than 4 miles. The ScanGauge is great because I can customise the display to show a variety of data while it shows a graph of running mpg around the current average,

eagle123

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Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
« Reply #26 on: January 11, 2018, 10:15:36 AM »
I keep meaning to block the lower grill for just that very reason. It takes almost 10 miles before my average mpg starts to recover after a winter start. And the majority of my daily journeys are less than 4 miles. The ScanGauge is great because I can customise the display to show a variety of data while it shows a graph of running mpg around the current average,

Petrol cars aren't that efficient due to their Otto cycle deisels burn more efficiently and are relatively 30 percent more efficient.
A interesting recent design by Mazda for their new sky active X engine marries both deisel and petrol advantages. It uses variable combustion cycles to mimic petrol smooth running to dedeil like torque and exonmy.


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culzean

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Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
« Reply #27 on: January 11, 2018, 11:21:25 AM »
Petrol cars aren't that efficient due to their Otto cycle deisels burn more efficiently and are relatively 30 percent more efficient.
A interesting recent design by Mazda for their new sky active X engine marries both deisel and petrol advantages. It uses variable combustion cycles to mimic petrol smooth running to dedeil like torque and exonmy.


If you take away the fact that Diesel fuel is heavier than petrol and contains about 20% more energy per litre it explains 'diesel efficiency' a bit LOL  - IMHO because of higher energy diesel should actually be 20% more expensive than petrol, also  a standard barrel of crude yields on average 20 gallons of petrol and only about 9 of diesel, another reason to raise diesel price, there is less of it.

The Mazda 'petrol-Diesel' direct injection is very interesting, my brother has new 1.4 Skoda  with similar technology and is very happy with its mpg.
« Last Edit: January 11, 2018, 01:21:58 PM by culzean »
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

Jocko

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Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
« Reply #28 on: January 11, 2018, 11:34:20 AM »
The Mazda 3 with Its Skyactiv-X Compression-Ignition Gas Engine is actually a petrol engine.

auntyneddy

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Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
« Reply #29 on: January 11, 2018, 02:20:47 PM »
Whilst this is a deviation from the query, much to the chagrin of some, my favourite couple opposite have an Audi and a Ford van. Dumber as I call the female ( this is what my Wife has  observed previously) comes out in pyjamas and starts the Audi ( diesel), this morning the headlights were shining into our bedroom so I timed her. 18 minutes between starting the car and driving off.  Not only an offence but as I used to tell motorist when I caught them leaving a car running while they went into a shop. If it gets stolen, you will have to go and collect it and the chances are your Insurers will not pay out for anything. At 30mph this Audi could be 7 miles away before she comes out. The van has not been taxed for some considerable time.
It might be a diesel but over a week I should think a fair bit of fuel is wasted not withstanding the pollution.
Does anyone know if the Audi is fitted with the very expensive 'particulate filter?' which I believe loves this sort of treatment.

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