Author Topic: Fuel consumption from full tank to empty vs frequent refill.  (Read 4830 times)

guest10626

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Re: Fuel consumption from full tank to empty vs frequent refill.
« Reply #15 on: September 16, 2021, 09:40:53 AM »
So how many litres did you get in ?

The tank is 40L so it's interesting as to how many litres left  = 5 km

The result is 4,79 Liters then.

sportse

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Fuel consumption from full tank to empty vs frequent refill.
« Reply #16 on: September 16, 2021, 09:41:05 AM »
Usually I always fill up between 1/2 - 1/4 of a tank left.

The only time I ran it down was the first dealer supplied full tank of cheap fuel as I wanted to use it up and refill with my preferred fuel.

It’s good to know that the range remaining display can’t be relied upon below 100 miles in case you need to go low though.

There is fuel stored in the fill pipe as well as the tank when you refill, so I estimate there might only be at most 3-4 litres remaining when the range display hits zero.

Not all of those may be usable depending on where the pickup pipe is in the tank.

guest10626

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Re: Fuel consumption from full tank to empty vs frequent refill.
« Reply #17 on: September 16, 2021, 09:43:28 AM »
I'm quite surprised that folks are prepared to believe the "range remaining" display and risk running out of fuel. Plenty of people have commented on the inaccuracy of the fuel economy calculation (aka the "fibometer"), and that data must be used in the range calculation. I have witnessed myself the range display (in my Mk 3) varying by +/- 30 or 40 miles whilst travelling only a few miles, so it's really not particularly accurate. But yet people are prepared to trust that they can travel 5km when the display says they can. I really don't get that.

I wasn't brave enough for 1 km.

guest9814

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Re: Fuel consumption from full tank to empty vs frequent refill.
« Reply #18 on: September 16, 2021, 09:48:07 AM »
So how many litres did you get in ?

The tank is 40L so it's interesting as to how many litres left  = 5 km
My last refill from 7km remaining, managed to refill 36l.
But back to my question do someone there tried refill after 200km?
And does this helps to reduce fuel consumption ?
Now after my last refill average on fibometer is 85MPG or 3.3l/100km distance from refill is 162km or 95 miles, I will refill after 2 bars disappears, and will do so several times on same fuel station and same fuel pump.

Neil Ives

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Re: Fuel consumption from full tank to empty vs frequent refill.
« Reply #19 on: September 16, 2021, 10:02:03 AM »
Was1929 the last year the Austin Seven had the petrol tank over the engine?
I'm not sure.  :)
Neil Ives

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Re: Fuel consumption from full tank to empty vs frequent refill.
« Reply #20 on: September 16, 2021, 02:58:44 PM »
Fuel has some weight, so the more fuel you are carrying, the worse will be your fuel consumption, albeit by a small amount.  I have had no worries in my Mks 2 & 3 about running down to an indicated zero miles remaining and slightly into negative territory, but only in the interests of reaching a known ASDA filling station to save a pound or two on the fuel price!
« Last Edit: September 16, 2021, 03:05:39 PM by Downsizer »

John Ratsey

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Re: Fuel consumption from full tank to empty vs frequent refill.
« Reply #21 on: September 16, 2021, 04:02:31 PM »
The handbook says that the low fuel indicator comes on when there's approximately 5.3 litres remaining in the tank. I think that's also the point at which the miles remaining is shown as zero. Honda doesn't want a breakdown due to lack of fuel.

My miles and fuel gauge observations suggest that the forecast miles remaining are fairly accurate down to 1/2 a tank and then the algorithm changes to converge on the zero miles with 5.3 litres remaining. The miles remaining estimate is also influenced by recent fuel consumption. However, while Honda's system is good for a normal drivetrain where crawling traffic due to a long jam can result in low mpg, the hybrid system can handle this situation without adversely impacting the fuel economy.
2022 HR-V Elegance, previously 2020 Jazz Crosstar

culzean

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Re: Fuel consumption from full tank to empty vs frequent refill.
« Reply #22 on: September 16, 2021, 04:58:30 PM »
I'm quite surprised that folks are prepared to believe the "range remaining" display and risk running out of fuel. Plenty of people have commented on the inaccuracy of the fuel economy calculation (aka the "fibometer"), and that data must be used in the range calculation. I have witnessed myself the range display (in my Mk 3) varying by +/- 30 or 40 miles whilst travelling only a few miles, so it's really not particularly accurate. But yet people are prepared to trust that they can travel 5km when the display says they can. I really don't get that.

Normally my tank never allowed to get below half empty....

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

peteo48

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Re: Fuel consumption from full tank to empty vs frequent refill.
« Reply #23 on: September 16, 2021, 05:46:08 PM »
I'm another who doesn't run the tank down. I tend to fill up when it's convenient to do so soon after I get past half full. On occasions I'll go down to quarter full (usually around 110 to 120 miles on the guessometer).

nowster

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Re: Fuel consumption from full tank to empty vs frequent refill.
« Reply #24 on: September 16, 2021, 11:46:52 PM »
Something to note is that if you're topping up before any of the bars on the fuel gauge go out (eg. with less then 5 litres) the car doesn't notice and range indicator does not increase.

guest9814

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Re: Fuel consumption from full tank to empty vs frequent refill.
« Reply #25 on: September 26, 2021, 08:11:12 PM »
Yes computer not recalculated remaining km after refill of 10l of gasoline, but then computer will recalculate remaining km.
Today after 2 bars of fuel gauge disappeared I  refilled  tank.
From reset of  Trip A   counted 327km  and 10.8l filled in tank, pump stopped automatically.
If after several refills of 10l each time MPG will not drop the only thing I can think is stale gasoline  in tank after almost month of driving without adding fresh gasoline.
And our gasoline without ethanol , what’s would happen with E10 fuel after month in fuel tank ?

Jazzik

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Re: Fuel consumption from full tank to empty vs frequent refill.
« Reply #26 on: September 26, 2021, 10:36:40 PM »
I'm sorry to say that this topic in my view is a total non-topic (is that proper English?). It looks like an empty tanlk.
Everyone will know by now that fuel consumption according to the BC is never exactly correct. Just refill the tank when it's almost empty. That can be when none, still one or maybe two bars are visible. Or when a particularly, extremely tempting gas station :-* comes into view of course.
I did my last tank filling when I still had some 10 km. reach according to the BC. Completely filled up I got 34.54 liters in the tank. So there was almost 5.5 liters left.

Difference in consumption between driving the tank (almost) completely empty or always refueling after some 200 km., topping up some 10 litres, is totally nonsensical. The BC might even show a difference, but it doesn't mean a thing, because that BC, as we know, isn't precise.
Theoretically, it's simple: by always driving with an almost full tank, you drag more weight than necessary and you drive less economically. Period!
The only way to determine actual fuel consumption is to divide the number of kilometres/miles driven by the litres/gallons tanked. An easy way is to use https://www.spritmonitor.de/

Oh... and you save the most fuel by doing short(er) trips by bike. And besides: it also seems to be very healthy...  :D


PS Stale gasoline...? After almost a month?
« Last Edit: September 26, 2021, 11:22:18 PM by Jazzik »
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DERMOT

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Re: Fuel consumption from full tank to empty vs frequent refill.
« Reply #27 on: September 26, 2021, 11:23:02 PM »
I would imagine by now everyone in UK now has a full tank of fuel, and no-one is going to risk leaving only a few km range left before heading to the local petrol station.

guest9814

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Re: Fuel consumption from full tank to empty vs frequent refill.
« Reply #28 on: September 27, 2021, 05:20:49 AM »
I'm sorry to say that this topic in my view is a total non-topic (is that proper English?). It looks like an empty tanlk.
Everyone will know by now that fuel consumption according to the BC is never exactly correct. Just refill the tank when it's almost empty. That can be when none, still one or maybe two bars are visible. Or when a particularly, extremely tempting gas station :-* comes into view of course.
I did my last tank filling when I still had some 10 km. reach according to the BC. Completely filled up I got 34.54 liters in the tank. So there was almost 5.5 liters left.

Difference in consumption between driving the tank (almost) completely empty or always refueling after some 200 km., topping up some 10 litres, is totally nonsensical. The BC might even show a difference, but it doesn't mean a thing, because that BC, as we know, isn't precise.
Theoretically, it's simple: by always driving with an almost full tank, you drag more weight than necessary and you drive less economically. Period!
The only way to determine actual fuel consumption is to divide the number of kilometres/miles driven by the litres/gallons tanked. An easy way is to use https://www.spritmonitor.de/

Oh... and you save the most fuel by doing short(er) trips by bike. And besides: it also seems to be very healthy...  :D


PS Stale gasoline...? After almost a month?

https://www.bp.com/content/dam/bp/country-sites/en_au/australia/home/products-services/fuels/opal-factsheet-storagehandling.pdf
Ok read please.

embee

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Re: Fuel consumption from full tank to empty vs frequent refill.
« Reply #29 on: September 28, 2021, 12:47:46 PM »
It never ceases to amaze me how worked up some folk get about such trivial things. The world will not come to an end with E10 fuel or leaving a tank half full.

The space above the fuel in a car tank is full of vapour, not air. All modern cars run with a positive pressure in the tank to help regulate evaporative losses. The pressure is generated by the volatile elements in the fuel coming out, excess is adsorbed in the carbon can (evaporative loss canister) which is then purged when the engine runs using the engine management system to draw air through the canister which carries the trapped hydrocarbons with it. No air is drawn into the tank, just through the canister.
The volatility of fuel (often described by Reid Vapour Pressure RVP) is regulated throughout the year according to market/climate. I'm out of touch with recent regs, but this gives an insight https://www.concawe.eu/wp-content/uploads/2017/01/rpt_97-53-2004-00588-01-e.pdf
Volatility is required for starting and combustion initiation etc., but too much means loss of a large amount of vapour and difficult fuel handling issues (vapour locking etc).

Alcohols such as IPA are used for de-watering systems, and some ethanol will do the same function. Fresh clean fuel with some ethanol can be quite useful for cleaning a fuel system, and will certainly update the volatility of older fuel, at least enough to get the engine started again after a winter lay-up for example. Modern fuel injected cars don't generally suffer starting problems because the fuel in the pipework to the engine and fuel rail (if used) cannot readily lose the volatile fractions, it id trapped in a closed system, so it has to be left for a long time to cause real issues. Once started and warmed up it will usually then run happily on any residual lower volatility fuel.
To start horticultural engines after winter I usually give a short squirt of brake cleaner in the intake, it is very volatile (often naptha/acetone/toluene etc) and usually gets them going.

If leaving a vehicle unused for any length of time it is usually desirable to either drain it completely (if practical), or fill the tank which minimises deterioration.

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