[AlanHo]

I brimmed the car today after running the tank virtually empty. The fuel warning light came on when the trip showed a range of 74 miles. When the range reached 30 the trip changed to a row of dots and the bottom bar of the fuel gauge started to flash. I was on the motorway and did 23 miles to the nearest service station where I brimmed the car with 60.73 litres - the most of have ever got in at any refuelling. The distance covered on this tank was 752 miles (1210 km) which is also a record and the average overall fuel consumption for the tank works out at 57.32 mpg (4.93 l/100km).

Here is a copy of my spreadsheet where I record all fuelling (I carefully brim every time) and the DPF regenerations I have noticed.

[Doggie 1]

Great record keeping Alan & a great result from your latest tank.
I'm looking forward to getting mine.

[Shambles]

Good work Mr Ho.

Does your spreadsheet contain macros, to perform some of the adjustments and ultimate final calculations? If so, could be a useful tool for others

[AlanHo]

Good work Mr Ho.

Does your spreadsheet contain macros, to perform some of the adjustments and ultimate final calculations? If so, could be a useful tool for others

For each fill I enter the date and the information in the 3 blue columns - Litres added, odometer reading, Avge MPG trip reading - and the spreadsheet does the rest.

Note :

I always brim the tank to the very, very, very top of the filler neck. This can take several minutes.

I always reset the average mpg trip at each fill and leave it to show the average since the car was brimmed each time

The odometer in my car is 1.8% slow - the spreadsheet makes an adjustment for this.  As reported in another thread, I compared the odo with the motorway kilometer distance boards over a couple of long journeys to measure the discrepancy.

The DPF regeneration odometer readings are when I first notice the sudden change in economy or when the Auto-stop is disabled. Regeneration continues for 15 to 20 miles and/or 20 minutes and I may not catch the actual start each time. Hence the odo intervals will not be dead accurate.


Anyone who wants a copy of the Excel file is welcome - PM me an Email address and I will reply with the file attached.
You will need basic spreadsheet skills to adjust the odo compensation in the file to suit your car and to use kilometers and litres/100km as appropriate.

[Doggie 1]

I admire your dedication in your striving for accuracy, Alan.
My only doubt would not be in the collection of your data, but in the exact placement of the motorway km posts. I wouldn't be placing too much trust in those because there are too many variables, such as who dug the hole, how the post was placed, etc. I would have seen those as more of a guide (guide post) than an accurate representation of exact distance travelled.
Unless something is significantly different in the U.K. as compared to Australia, which I guess is entirely possible.
Having said that, I'm happy to accept the trip computer readout in mine. 

[Dazzler]

That is a great result for an i30 with a DPF Alan (congratulations)

 This car seems to be getting closer to the economy figures you hoped for in the previous one. 

[AlanHo]

I admire your dedication in your striving for accuracy, Alan.
My only doubt would not be in the collection of your data, but in the exact placement of the motorway km posts. I wouldn't be placing too much trust in those because there are too many variables, such as who dug the hole, how the post was placed, etc. I would have seen those as more of a guide (guide post) than an accurate representation of exact distance travelled.
Unless something is significantly different in the U.K. as compared to Australia, which I guess is entirely possible.
Having said that, I'm happy to accept the trip computer readout in mine. 

I have also used the sat-nav to check the odo on a long straight section of motorway to cut out any possible error due to bends (not that I believe there is one). The sat-nav produces an identical result. One of my friends is a retired civil engineer who was project general manager for the UK M40 motorway a few years back. He claims that the distance marker boards are accurate to within a couple of inches - even over the total length of the motorway. The boards placed on the side of each dual carriageway represent the distance measured at the centre line of the carriageway when originally constructed. Later widening of the motorway by adding extra lanes may move the centre line over - introducing small errors board to board, but not overall. He says it is imperative that the markers are accurate because future maintenance and development activities rely upon them for positioning.

[Dazzler]

Your attention to detail in astounding Alan.. I only wish God had been as thorough when he made me 

[Doggie 1]

Every perfect creation has to have a draft copy.   
(I think I was born just after you, wasn't I?  )?

[Shambles]

I only wish God had been as thorough when he made me 

Sound words there Dazz, but I do believe they broke the mould before they made me

[Keith]

Is there absolutely no contention, that fuel may be lost via the filling cap or overflow / venting system when carefully brimming the fuel tank to its absolute maximum?

[AlanHo]

Is there absolutely no contention, that fuel may be lost via the filling cap or overflow / venting system when carefully brimming the fuel tank to its absolute maximum?

My usual BP garage is only half a mile from my house and on just one occasion I filled up very early one morning - drove home immediately, parked the car on the drive and went indoors. 2 hours later the sun was shining on the back of the car and there was a small amount of diesel on the drive. I assume the cold morning when I refuelled then the hot sun on the car had cause expansion. Since then I have always tried to refuel when I set out for a journey or well before my destination so I use some fuel before parking up.


Considering Hyundai state that the tank has a capacity of 53 litres - I am surprised I managed to squeeze almost 61 litres in.  Others on the forum have also stated that they have got more than 60 litres into the tank without any mention of any fuel loss.

[Doggie 1]

I drive immediately after filling so haven't experienced fuel loss.

[baroudeur]

Is there absolutely no contention, that fuel may be lost via the filling cap or overflow / venting system when carefully brimming the fuel tank to its absolute maximum?

My usual BP garage is only half a mile from my house and on just one occasion I filled up very early one morning - drove home immediately, parked the car on the drive and went indoors. 2 hours later the sun was shining on the back of the car and there was a small amount of diesel on the drive. I assume the cold morning when I refuelled then the hot sun on the car had cause expansion. Since then I have always tried to refuel when I set out for a journey or well before my destination so I use some fuel before parking up.


Considering Hyundai state that the tank has a capacity of 53 litres - I am surprised I managed to squeeze almost 61 litres in.  Others on the forum have also stated that they have got more than 60 litres into the tank without any mention of any fuel loss.

The tank capacity is the actual volumetric capacity of the container and excludes the filler pipe.

[marti30]

Several times recently I've compared my tripmeter with English motorway kilometer marker posts over distances of 70-90 miles. On the M1 my odometer under reads but it over reads on the M25. This seems to be the case in both directions and when I've made a day return journey using both motorways without making any adjustments to the car. When comparing distance recorded with distances suggested by online route information the odometer under reads suggesting to me that that the car's odometer is consistently inaccurate in its under read and that the M25 marker posts are wrong. Perhaps someone else would like to put this to the test when using these motorways. I've not had the opportunity to compare my odometer with the posts on another motorway to make it a best of three. 

[AlanHo]

I have checked my odo against the marker boards on the M5 from The Midlands to Exeter and the M6 up to Carlisle. Both gave me the same result - my odo is 1.8% slow.

[Phil №❶]

Actually, how do you get an accurate reading of distance anyway.

The odo is gear driven and the car travels on the tyre tread, so depending on the profile and wear of the tyre, for every mm of + / - of tyre radius, we get 3.14..... mm variation don't we 

Actually, how do you get an accurate reading of distance anyway.

The odo is gear driven and the car travels on the tyre tread, so depending on the profile and wear of the tyre, for every mm of + / - of tyre radius, we get 3.14..... mm variation don't we 

No, 6.28.

[AlanHo]

The rolling radius of a tyre is not affected in direct proportion to tread wear and does not change very much within the normal tread wear limits. The tyre rolling radius is quite  a bit smaller than the unloaded radius of the tyre tread.  Hence the odo remains reasonably consistent throughout the life of the tyre.

[Phil №❶]

Actually, how do you get an accurate reading of distance anyway.

The odo is gear driven and the car travels on the tyre tread, so depending on the profile and wear of the tyre, for every mm of + / - of tyre radius, we get 3.14..... mm variation don't we 

No, 6.28.

I knew that, just seeing who was awake 

[baroudeur]

Several times recently I've compared my tripmeter with English motorway kilometer marker posts over distances of 70-90 miles. On the M1 my odometer under reads but it over reads on the M25. This seems to be the case in both directions and when I've made a day return journey using both motorways without making any adjustments to the car. When comparing distance recorded with distances suggested by online route information the odometer under reads suggesting to me that that the car's odometer is consistently inaccurate in its under read and that the M25 marker posts are wrong. Perhaps someone else would like to put this to the test when using these motorways. I've not had the opportunity to compare my odometer with the posts on another motorway to make it a best of three.

Motorway marker POSTS  every 100 metres are supposed to be very accurate. 

As the M25 is circular the  clockwise lane 1 carriageway must be longer than the anti-clockwise lane 1..............................................by how much?


Edit:   This has been the subject of much scrutiny.  Apparently anything between 58 and 75 metres is the answer.

[baroudeur]

The rolling radius of a tyre is not affected in direct proportion to tread wear and does not change very much within the normal tread wear limits. The tyre rolling radius is quite  a bit smaller than the unloaded radius of the tyre tread.  Hence the odo remains reasonably consistent throughout the life of the tyre.

I suspect that the difference between a new tread depth of 8mm and a worn tread at  1.6mm depth would be reflected in the rolling radius being 6.4mm less.

[marti30]

Perhaps someone else would like to compare their odometer and/or satnav device against marker posts on the M25, M1 and other motorways to confirm whether the marker posts are always as accurate as claimed. In my experience my odometer always under reads against the posts on the M1 and over reads against those on the M25 and this is the case in both directions. On the M1 the under read is about 1.7% which suggests that my odometer is similar in its under read to Alan's. I sometimes take the long way round the M25 to avoid congestion and/or the Dartford Troll (lurking in the shadow of the bridge and taking money from travellers). Next time I do this I will once again compare the indicated distances. I suspect the clockwise and anti clockwise posts are not always directly opposite each other and show different distances accordingly. The M11 is a bit too short for comparing odometers with marker posts but when I have done so once again my odometer appears to under read.

[marti30]

I've just realised that there's a fair bit of repetition in my posts and apologise for boring you. Please feel free to edit them.

[Shambles]

I've just realised that there's a fair bit of repetition in my posts and apologise for boring you. Please feel free to edit them.

Your wish is my command

[Phil №❶]

The rolling radius of a tyre is not affected in direct proportion to tread wear and does not change very much within the normal tread wear limits. The tyre rolling radius is quite  a bit smaller than the unloaded radius of the tyre tread.  Hence the odo remains reasonably consistent throughout the life of the tyre.

I suspect that the difference between a new tread depth of 8mm and a worn tread at  1.6mm depth would be reflected in the rolling radius being 6.4mm less.

So that's (6.4 X 2)X 3.14 = 40.21 mm less distance covered / revolution


Note that the 6.4 is not quite correct because 1 side is loaded and 1 side is not, but the unloaded side would be smaller to some degree because the tread has worn away. 

[Dazzler]

I just use the trip computer  (it's easier) 

Occasionally I do a brim to brim calculation just to compare, but I would run off the road trying to compare guide post distances with my odometer 

[Doggie 1]

 

[baroudeur]

I suspect that the difference between a new tread depth of 8mm and a worn tread at  1.6mm depth would be reflected in the rolling radius being 6.4mm less.

So that's (6.4 X 2)X 3.14 = 40.21 mm less distance covered / revolution
Note that the 6.4 is not quite correct because 1 side is loaded and 1 side is not, but the unloaded side would be smaller to some degree because the tread has worn away. 

6.4mm is the difference between a new tyre tread  and one worn to legal minimum depth.  The speedometer and odometer use wheel revolution to record speed and distance.  But which wheel?