Pessimistic Fuel Gauge

[madasafish]

None of you have ever lived!

In the 1980s I drove my very own Jaguar XJ6..and towed a caravan
At 60mph err,, 70mph.

I recall each of the two fuel tanks (switchable) held about 10 gallons (alcohol. age and time mean I cannot recall exactly_)
When you achieve 13mpg , switching fuel tanks and visiting fuel stations become a common occurrence..

[Westy36]

13mpg! Blimey. Do you have your own oil field Sheik madasafish? 
 

[nowster]

So, thought I would see 'how low I dare go' the other day. Little Jazz reckoned he was about bone dry and only 23 miles left in the tank. Right then, I reckon I'll get about 40 litres in...

At an indicated "empty" you've got between 6 and 8 litres left in the Mk2 Jazz. It's all due to the unusual shape of the tank. They made a feature out of it by marketing it as a "reserve".

[Jocko]

I had a Mk 1 Triumph 2.5 PI in which the fuel injectors were shot. When I sold it I told the guy, "I have to be honest. I have had 18 mpg out of it.". What I didn't tell him that was the best I had had. 9 mpg was my average. I had to replace the sooty spark plugs every day. Luckily I had about 5 sets of them (30) and access to a sandblaster.

[150234]

I tend to fill the tank when the needle drops below the half way mark. Today, the needle was suggesting a nearly empty fuel tank. Only took 33.08 litres to fill it! I was expecting to get more in. 

The fuel gauge on Honda Jazz’s are indeed very pessimistic. The light on my mk1 Jazz comes on with around 9 or so litres left (meaning a 34 litres fill up) but because I’m an idiot I like to stretch it and play the lottery. Current personal record is 40.1 litres in a 42 litre tank, I really was running on fumes that day.

So many people panic about the fuel light when they really don’t need to. Like I said, my fuel light comes on with 9 litres left so at 45mpg that rices me around 90 miles of running before empty so people who rush to the pump the second the light comes on don’t need to. If the next fuel pump isn’t for 30 miles, don’t worry about it.

[MartinJG]

This may divide opinion and I'm certainly no expert on these things, but a mechanic I know told me many years ago that consistently using almost your entire fuel tank was a good thing as you were more likely to avoid poor quality fuel accumulating at the bottom (because it would have been processed by the engine for its intended purpose).

Ever since then, and on a range of previous cars, I have almost always waited for the fuel warning light to come on before filling up (when there is approx. 5-7 litres left in a 40 litre tank). Not sure if that mechanic was right or I've just been lucky, but I've never had any engine problems.

I would suggest your mechanic has expressed an opinion . If in doubt, I think the prudent approach is to avoid the risk of any rubbish (dead flies, dust, dirt, you name it) that has collected at the bottom of the tank, especially with older vehicles.

[TnTkr]

I have intentionally driven fuel tank empty on many cars to see where the needle goes when the tank is empty and how much fuel can be filled then. And in all those cars the needle has fallen below the empty line before it's all used.

Haven't done it with my GK Jazz, because digital fuel display has so coarse resolution and it will not present anything less than empty. Would be nice to see the volume though...
 

[TnTkr]

This may divide opinion and I'm certainly no expert on these things, but a mechanic I know told me many years ago that consistently using almost your entire fuel tank was a good thing as you were more likely to avoid poor quality fuel accumulating at the bottom (because it would have been processed by the engine for its intended purpose).

Ever since then, and on a range of previous cars, I have almost always waited for the fuel warning light to come on before filling up (when there is approx. 5-7 litres left in a 40 litre tank). Not sure if that mechanic was right or I've just been lucky, but I've never had any engine problems.

I would suggest your mechanic has expressed an opinion . If in doubt, I think the prudent approach is to avoid the risk of any rubbish (dead flies, dust, dirt, you name it) that has collected at the bottom of the tank, especially with older vehicles.

Both approaches are difficult to give reason. The intake of the fuel line is always at same level from the bottom no matter how much fuel there is in the tank. Only the rubbish on the surface can get into the system if driving until the tank is empty.

[culzean]

Both approaches are difficult to give reason. The intake of the fuel line is always at same level from the bottom no matter how much fuel there is in the tank. Only the rubbish on the surface can get into the system if driving until the tank is empty.

I agree,  the intake level does not change as the fuel level decreases, so any water ( which is heavier than petrol ) would be sucked up whether tank was full or empty.   There is a large filter in the tank so and solid debris on the 'surface' of the fuel should not get through either.  Once you have run a car to empty light once you should know how much fuel is left anyway. IMHO Jazz reserve is better than only having 1 litre left when light flashes ( service stations in UK these days seem to be larger but are also further apart ).  Personally I never really let my tank get below half way because you never know when an emergency may arise and you need to use car.

[Kremmen]

Same here, topup at 50% left ....... because you never know

[RichardA]

I had a Mk2 Fiat Punto where the low fuel light used to come on very early, just under a quarter of a tank if I remember, much earlier than on any other make I've owned. I learn't to drive in Fiat Uno and that would the same, my driving instructor just said to ignore it!

[Kremmen]

Same here, topup at 50% left ....... because you never know

Vindicated ?

Just took a short walk to my local Tesco, 06:20, and there is a nose to tail procession as they have to go round the roundabout and back out to the main road as they are shut, run out.

[Neil Ives]

[smug]
I am very happy that I filled our MK4, day before yesterday. I should not need to refill until the current fuel crisis is over.
[/smug]

[d2d4j]

Hi

There is no fuel crisis apart from the perceived fuel crisis the panic buyers are creating!

Many thanks

John

[JimSh]

Hi

There is no fuel crisis apart from the perceived fuel crisis the panic buyers are creating!

Many thanks

John

But what will be the next crisis?
Don't panic Mr Mainwaring !
https://www.theguardian.com/business/2021/sep/24/how-will-energy-crisis-pandemic-brexit-affect-uk-households
https://www.theguardian.com/society/2021/sep/25/fears-over-nhs-plan-to-close-all-local-ambulance-stations-in-london