How much fuel left when Reserve light comes on?

[dcr69]

I did my first proper tank refill yesterday on my D4 FWD Manual.

I am used to computers that fib as to how much fuel is left (my Toyota would say I had a range of 20 miles when I could put on 55 litres in a 60 litre tank).

Anyways, being dumb, and making a 70 mile motorway journey, I ignored the Reserve light (which came on at around 50 miles left) and went off the trip computer telling me the range left.

When it got to 20 miles left I decided to leave the motorway and get to a fuel station.

On the slip road (uphill) the range went from 20 miles left to "---" and stayed like that for 2 miles to the petrol station.

I was expecting to get about 65 litres into the fuel tank.

I actually managed to put in 73.08 litres - definitely NOT something that I am proud of
Bear in mind the tank is officially 70 litres, plus the plumbing from the filler cap.

Incidently, I managed 777 miles on the tank and averaged 48.33mpg with a mix of
- about 500 miles on the motorway, locked in cruise control at 56mph - an indicated 58 mph on the computer - hey, they always overestimate, but GPS never lies
- about 200 miles on decent windy A-roads, speeding.
- the rest around town

So, from here on I will search for a fuel station when the reserve light comes on.

Has anyone ever run out of fuel, or run the fuel levels so low they got more than 73 litres in?

[RoyMacDonald]

Originally Posted by dcr69

I did my first proper tank refill yesterday on my D4 FWD Manual.

I am used to computers that fib as to how much fuel is left (my Toyota would say I had a range of 20 miles when I could put on 55 litres in a 60 litre tank).

Anyways, being dumb, and making a 70 mile motorway journey, I ignored the Reserve light (which came on at around 50 miles left) and went off the trip computer telling me the range left.

When it got to 20 miles left I decided to leave the motorway and get to a fuel station.

On the slip road (uphill) the range went from 20 miles left to "---" and stayed like that for 2 miles to the petrol station.

I was expecting to get about 65 litres into the fuel tank.

I actually managed to put in 73.08 litres - definitely NOT something that I am proud of
Bear in mind the tank is officially 70 litres, plus the plumbing from the filler cap.

Incidently, I managed 777 miles on the tank and averaged 48.33mpg with a mix of
- about 500 miles on the motorway, locked in cruise control at 56mph - an indicated 58 mph on the computer - hey, they always overestimate, but GPS never lies
- about 200 miles on decent windy A-roads, speeding.
- the rest around town

So, from here on I will search for a fuel station when the reserve light comes on.

Has anyone ever run out of fuel, or run the fuel levels so low they got more than 73 litres in?

The fuel tank holds 70 litres but the station fuel pump might not be accurate.

The range left is a product of the last few miles you drove but if the level in the fuel tank falls too low the computer cannot do an accurate calculation so you just get the dashes. The fuel system can be ruined on a diesel if it completely runs out of fuel. A friends car now has a fit of the jerks at random ever since she ran out of fuel. People who have done it here have been OK though. Volvo do warn not to run out of fuel in the handbook. In my friends case the main dealer is saying the only way to fix it is to replace the whole fuel system.

[Harvey1512]

The fuel station pump has to be accurate. Trading standards check them every so often. Some people talk about secret storage in cars that mfrs don't tell owners about. Sounds a bit conspiracy theory to me but maybe that is true.

One possible theory is the amount fuel expands and contracts. When the tank is first checked the temperature will be whatever, let's say 20°C. When you filled up recently, bearing in mind the fuel is stored underground, it may be 6-8°C. This would reduce the volume of the fuel so that you can get more in than if the temp was the standard level.

I have only got to 0 miles left once and it was by accident. The car I was driving was quite new and would drop suddenly at the end and I was not near a fuel stop. I drove meticulously at 50mph and was quite pale. I now get no lower than a quarter before filling. Lesson learnt.

[St James]

I've never done it in my XC60, but like Harvey, I did do it in a BMW once coming out of London late at night.........I think the range said 1 mile just as I pulled into the garage......never been so worried (it was about 12.30pm, I didn't know where I was, and I had no sat nav).

[andymcp]

I left the house this morning with 120 miles of range left. Shortly after leaving the fuel indicator went red, with 110 miles range left. Add in some cold engine miles, uphill motorway and wet conditions and 5 miles later the range said 65 to go....

Stuck with it and 47 miles later range was back to 75 to go. Only needed 67 litres to the first click of the pump. Most I've managed to squeeze in was 75 litres. I had totally brimmed the car and also had, from memory, 20 miles indicated range left before I started filling up.

[RoyMacDonald]

Originally Posted by Harvey1512

The fuel station pump has to be accurate. Trading standards check them every so often.

I've never seen a fuel pump being checked in 50 years of motoring. There have been big reductions in the number of trading standards officers recently as well. What you say may be true but I can find no proof either way. I've looked at a number of council sites and no work on checking garage forcourts were listed as being done. Mostly cars, food and counterfeit goods.

The most I've ever filled is 69 litres but I don't have the nerve to go any further.

[id5]

Originally Posted by Harvey1512

The fuel station pump has to be accurate. Trading standards check them every so often
...
fuel expands and contracts. When the tank is first checked the temperature will be whatever, let's say 20°C. When you filled up recently, bearing in mind the fuel is stored underground, it may be 6-8°C. This would reduce the volume of the fuel so that you can get more in than if the temp was the standard level.
...

Expansion is why planes are fuelled by weight and not by volume and also why cars are more efficient when it is colder.

But worry not because the pump is measuring the fuel as it is drawn at the temperature of the storage tank, and not after it has expanded to air temperature.

The average 15°C temp change between the storage tank to the car tank increases the amount of fuel by approximately 0.5 litre in an average size tank full. That expansion also dilutes the amount of energy in each litre making the MPG less in summer than in winter by about 8%.

[flipper234]

Originally Posted by RoyMacDonald

I've never seen a fuel pump being checked in 50 years of motoring. There have been big reductions in the number of trading standards officers recently as well. What you say may be true but I can find no proof either way. I've looked at a number of council sites and no work on checking garage forcourts were listed as being done. Mostly cars, food and counterfeit goods.

r.

Sorry but the pumps at all petrol stations are subjected to regular testing by not only Trading Standards, but also by Her Majesties Customs and Excise. You may be lucky and see one or the othern in their white mobil lab/van wandering about on forecourts with large old fashion looking copper containers.

[Whyman]

If you look on the fuel pump there will be a sticker telling you when the pump was last tested. Not sure if Trading Standards do it any more, more likely to have been put out to contract

[wimorrison]

Originally Posted by flipper234

Sorry but the pumps at all petrol stations are subjected to regular testing by not only Trading Standards, but also by Her Majesties Customs and Excise. You may be lucky and see one or the othern in their white mobil lab/van wandering about on forecourts with large old fashion looking copper containers.

A tad out of date as Customs and Excise was superceded in 2005 by HMRC = Her Majesty's Revenue and Customs