Exactly, people need to remember these cars are used all over Europe, a good designer will do the fuel warning maths based on a country/region, that has few filler stations. He will look at the longest stretch of road and distance between the furthest filler stations, then add a few percent on for silly people.

It would be nice to think that so much thought went into the calculations - but seriously?

Warrior193.

The range to empty is calculated using the speed sensors, trip distance etc and the fuel consumption as calculated by the ecu. This is then compared to the level that the fuel gauge is saying (which is never going to be 100% accurate) before a simple calculation of the distance on the fuel in the tank. I have seen the range to empty go up on my mk1 as the mpg increases on the trip computer.

As said, you will never get a completely empty tank, as the pick up doesn't go all the way to the bottom of the tank.

The OP really needs to dust his instruments!

I got 15 miles into the '0' showing in my Fabia, I was sweating buckets as I was slightly lost and there was no mobile signal for me to find a petrol station on Google Maps! I happened to pass one and filled it up, which was a relief. Still didn't get the full 45 litres the Fabia is supposed to take in it, so it's not just the Octy that's conservative in that way. But I'm glad it's that way round- far better to sweat a bit about it and still have fuel in the tank than to think all is good before conking out on the side of the road!

 

Also interesting how, after a load of stop/start city driving, the range can increase as you head out onto the motorway, especially on the 50 mph section just south of Manchester! Last time I did that I set off with it saying about 410 miles range, and it got to 450 before starting to decrease again about 50 miles in!

Why on earth anyone would want to run a tank all the way down is beyond me

 

This is useful to know so I thank the OP.

The empty warning is shown to be too sudden. Sometimes you don't have a handy filling station so a fill-up requires making a special trip, a detour, stopping at a motorway services (aka bandit country) or some other inconvenience. Now we can avoid some of those if we're careful. 

I never got more than 43 litres into mine but I never ran it down to zero.

 

To me, an innacurate fuel gauge is useless.

 

I'd rather all manufacturers displayed how much fuel was left in the tank rather than this Mickey Mouse "20 miles to empty" malarkey.  Simple enough to do given that they know the weight of an empty tank and they know the weight of a tank full to capacity.......once you know those two metrics you can calibrate the reading to within an ounce of fuel.

If it was that easy all the cars would have 0.01 litter accuracy, but the fact is :

- the car is movin all the time which means longitudinal, lateral and vertical accelerations that moves fuel in random directions continuously

- density of fuel varies with ambient temperature

- not all fuels are within the same specifications in all the countries

- We think liters (or gallons) of fuel in the tank but the ECU thinks grams of fuel injected in the chamber

- etc...

Got mine down to 0 miles remaining last week, turned up at the petrol station and my fuel flap door was stuck shut. Was definitely sweating at this point, as I didn't fancy leaving without fuel. With some help from Skoda Assist, I managed to get the fuel flap open and put in 48.2 litres.

 

Gonna fill it up a bit sooner on this tank!

The most I've ever managed to get into the Octavia was 48.5 litres - with only a little rocking, range remaining was stated as 12 miles (430 miles on the trip meter) but that was my chicken point.

Warrior193 

The OP really needs to dust his instruments!

 

I know, wish i had time to clean it - When it was new i was fairly fastidious with the cleaning. bought a foam gun and everything - but when picture was taken, and now, not so much! I'm even going to let the dealers clean it when it goes for a service. I hope they don't use sponges . . . 

 

This is useful to know so I thank the OP.

The empty warning is shown to be too sudden. Sometimes you don't have a handy filling station so a fill-up requires making a special trip, a detour, stopping at a motorway services (aka bandit country) or some other inconvenience. Now we can avoid some of those if we're careful. 

 

It's more laziness . . but it means i can leave it until the weekend and a supermarket fill up with an extra 8p off a liter, rather than diving into the 8p per liter more expensive place in a panic that the computer says zero.

 

Got mine down to 0 miles remaining last week, turned up at the petrol station and my fuel flap door was stuck shut. Was definitely sweating at this point, as I didn't fancy leaving without fuel. With some help from Skoda Assist, I managed to get the fuel flap open and put in 48.2 litres.

 

Gonna fill it up a bit sooner on this tank!

 

Someone else mentioned the petrol engines run theirs down to a true zero faster - I imagine you get through a lot of fuel with a 220 TSI?! I have a hard enough time not playing with the 150 diesel . . .

Someone else mentioned the petrol engines run theirs down to a true zero faster - I imagine you get through a lot of fuel with a 220 TSI?! I have a hard enough time not playing with the 150 diesel . . .

Usually a tank per week (somewhere between 300-350) miles depending on what kind of journeys I've done. It does seem to go from fuel light to 0 miles quite quickly though. I had a 52 mile trip to make yesterday with a 70 mile indicated range. Filled up beforehand this time to be sure I wouldn't get caught short!

To me, an innacurate fuel gauge is useless.

Absolutely. If I fill up with fuel as soon as the warning light on my Mk1 Focus comes on it takes exactly 45 litres, which I know leaves 10 litres which is good for about 90 miles. The warning light on the Octavia seems to be much less precise.

Don't you love fuel warning lamp roulette game?

This week I saw a guy park his car on a hill. Hazards flashing. Climb out with green 5L fuel can. I knew exactly where the fuel station was about a mile away. That's exactly where he was heading.

I considered pulling over to give him a lift but the bugger was smoking so I left him to it as I was hurrying on taxi duty. Stupid arse.

Good planning to carry a fuel can. But so so stupid to to run out. Why would you?

I don't always wait for the lamp, but it's always "brim full" - "drive" - "brim full".

I fill when it suits me.

Good luck to the players.

ps - yesterday's routine, planned, fill up was 44L with the dash reading range = 20 miles.

The most I have squeezed into the tank is 52.5l not bad for a 50L tank

The OP really needs to dust his instruments!

 

Saved me from making the post 

The most I have squeezed into the tank is 52.5l not bad for a 50L tank

 

Dodgy calibration on the dispensing pump?

 

Quite common even though Trading Standards Officers inspect regularly.

This has puzzled me since I got a MK11 CR Superb, my old Mk1 would fill to brim and show up to 700 mile range. I would drive it up to 120 miles with no movement on gauge then it would race to 3/4 tank. My replacement Mk11 fill to brim and show about 650 range, within 20 miles of local driving the gauge starts moving.

Once the MK1 gauge started moving it was pretty linear on the gauge however the MK11 gauge has a mind of its own. If i start a med-long journey following previous short ones then the gauge will be pessimistic on start, but once my MPG is up for the current trip then the gauge will increase a couple of segments. 

I think this shows that the fuel gauge isn't showing an accurate volume of fuel but an ECU reading of fuel remaining at current MPG. Thats my theory anyway, thus I refuel early and don't worry how the damn car works out how much fuel is left  :sweat:

Petrol

By far the easiest way to prevent fueling/ range concerns is.....

Fill up more often.

Works for me any way.

I never let it get below 1/4 full

Edited 13 December, 20169 yr by Bristolf2b

Dodgy calibration on the dispensing pump?

 

Quite common even though Trading Standards Officers inspect regularly.

If that had happened only once I would say that, but have regularly put more than 50L in from different pumps at different service stations

Good that @jthyssen posted proof of his real life experience of a 55L fill because I was just about to cite it myself.

I'll presume he drove into the station without the engine coughing and spluttering.

 

Most manufacturers understate the true capacity of their fuel tanks. Why? Because there are dumb asses out there who insist on running out of fuel, even when the gauge is indicating empty. My daughter has done it twice and mobile reception is patchy where she lives.

Or... they are just being conservative and it then covers manufacturing tolerance issues or airlocks encountered when filling.

 

In VAGs case it is fair to assume the tank is at least 5 litres larger than published across the range.

So in the mk3 Octavia the standard 50L tank can probably hold (at least) 55L and the 4WD models 55L will hold (at least) 60L

 

With regard to fuel gauge accuracy,  warning lights, and distance to empty indications? Well it does seem there is an element of pot luck as to how good your set are. It does seem much more common for diesel models to get unduly early warnings of low fuel. indicating that it is really not good for modern high pressure diesel injections systems to run out of fuel so it is probably a feature of  manufacturer conservatism.

I have probably experienced more variations in gauge accuracy and behaviour between individual cars than between manufacturers but you get used to the characteristics of your particular vehicle and account for its foibles.

The really annoying gauge (for me) is the one that moves in steps of a quarter of a tank at a time, you think you are doing well and then it plummets.to empty after a bend or bump.

 

'Distance to Empty" estimations will only be as good as the fuel gauge is accurate.

My experience is that the 'since refuel' information set (distance travelled and average consumption) when set to kilometres can be used to accurately assess how much fuel is left in the tank, but that is probably more difficult for UK residents who measure/display distances and consumption in miles and mpg and yet fill up in litres.

 

I should also add my current 1.4tsi fuel gauge, empty indicator and distance to empty are workably accurate although the first 'half' of the tank is 30L and the second 'half' is closer to 20L on my usual 50 litre from 'empty' fill.

Edited 13 December, 20169 yr by Gerrycan

Volvo S60 T5 hire car a few years ago in the states, took out the prepaid gas option and was told to bring it back empty.

Distance to airport on last day was 120miles, range showed 100.

once on freeway range improved.

Distance 80 miles, range 100

distance 50 miles, range 80

Distance 30 miles, range 50

got to 10 miles out and range 0 with constant beeps and fill up now warnings

made it without coughing but not fun for last few miles dreading running out of fuel and possibly missing plane.

Leason learned...don't like that kind of stress.

car was wonderful though, stupidly quick (US got a 260HP version)

I complained that a hire van from my old employer was empty when it was delivered to me. They said it's OK, just leave it empty when we pick it up.

I don't think theyd have said that if they knew I have a transfer pump

Edited 14 December, 20169 yr by StevesTruck

Once the MK1 gauge started moving it was pretty linear on the gauge however the MK11 gauge has a mind of its own.

Fuel gauges are normally driven directly from a float in the tank, so if the tank is a simple shape such as a rectangular "box" then the gauge will be very close to linear.

 

But with the increasing trend to odd shaped fuel tanks that fit in and around things such as rear suspension, exhaust pipes, etc. then the level of a float is very unlikely to be linear with quantity of fuel in the tank.

 

You could argue that car manufacturers should apply a calibration curve to the float level and display that linearised value on the fuel gauge. But that would cost them time & money to measure/calculate the curve and to add the linearisation code to the instruments firmware, and not enough people complain about or don't buy a car because of a non-linear fuel gauge - so there's no return on investment for them to do that, so they don't!

Edited 14 December, 20169 yr by PetrolDave

But in coding there are 3 (I think) fuel tank profiles selectable but whether that handles capacity or shape I do not know but someone may