Fuel gauge accuracy

[Cowgirl]

On my mk4 Yaris I can access 3 fuel gauges, the mileage to refuel, on MyT app the percentage remaining and the traditional gauge made up of 8 bars. My question is which one is most accurate? Also after the 8 bars on the traditional gauge is there any reserve?

[FROSTYBALLS]

As regards the reserve, in your owners manual, check the index under warning lights for 'low fuel light', and that should indicate how much fuel is remaining when the low fuel light illuminates - that is your reserve.

[Bernard Foy]

Low fuel warnings are just given as an indication of low fuel and the mileage left in the tank is variable according to the driving conditions and how the car is driven. I wouldn’t as a general rule drive more than 50 miles after the low fuel warning ⚠️ 

[AlJ]

I think, despite the massive advances in car technology, that 'all' fuel gauges should be treated with a pinch of salt, unless you're driving a race car! They're indicators, more than anything else. For instance, before now, I've driven two or three short trips (5 miles or so) after filling up and the MyT app has still shown 100%. Drive the shortest distance after that and it's 94% or whatever, like it's suddenly caught up. 
Of the different methods, the mileage to refuel is probably the most "accurate", for want of a better word, as it's giving you an indication based on your current driving style but even that will change if you speed up, go up more hills, etc. 

[Cyker]

I will say the Mk4's fuel gauge is the least terrible/inaccurate of all the Yarisusuessesis I've had - The Mk1 was definitely top heavy but the Mk2 was particularly abysmal - 300 miles on the first half, 80 miles on the second half! I know it's a V-shaped tank but would it have killed them to calibrate it or put in a correction curve?! It's not like this was an unknown problem from the Mk1!

It's still slightly skewed to the top in the Mk4 but nowhere near as badly as the Mk1 or especially Mk2.

[Starensis]

When the Range hits 0, you normally have at least a gallon in reserve.

[Cowgirl]

2 hours ago, Starensis said:

When the Range hits 0, you normally have at least a gallon in reserve.

Thanks, that’s really helpful

[Cyker]

Wouldn't recommend experimenting with that too much without a jerrycan handy tho'  

[Cowgirl]

I don’t plan on getting to 0!

 

My last Yaris I got to 6 miles left, that was scary enough for me!

[Cyker]

Probably sensible!  I haven't tried the low fuel experiment on the Mk4 yet, but tried it on my old diesel Mk1 once - Drove 100 more miles on the last flashing fuel-gauge block before I chickened out and dived into a petrol station  

I know the Mk1 diesel is a smegging efficient car, but Toyota must be really conservative with the reserve fuel!!

I tend to refuel my Mk4 with around a quarter tank left and that usually takes ~26 litres, so there's still 10 in the tank in theory!! (Still can't believe I can get 400 miles out of 26 litres of petrol, esp. with the way I drive - It's madness!  )

[Roy124]

We got to zero in Corolla on our test drive.  The low fuel light came on when we were 50 miles from base.  We nursed the car and pulled in to a filling station only to find we had no idea how to open the filler.  We continued as fast as we could before the fuel ran out (joke) and limped into the garage with the gauge hard below empty.

We were assured there was plenty left.

Best way, fill up.  Half full fill up again and note fuel up load.  Do it again at a quarter full.  Do it again at low light on.  This will give you some idea of gauging accuracy.  From my observation 1/2 is just that a quarter is pessimistic and empty happens not long after.  You don't need to run to empty to find out.

[bathtub tom]

I did put 5 litres in a can in my boot to try and find out what the reserve was, as I'd never got more than 32 litres in when the light came on and range was at zero. This in an advertised 40 litre tank.

I did about 40 miles with the light on and range at zero, but it was a wet Sunday evening and I was about to join the A1. I didn't fancy standing on the side of that, while I poured some in the tank and tried to re-start it. I got 36 litres in it without using any of what was in the can!

I wonder if the tank will hold 40 litres.

[Spo2]

2 hours ago, Cyker said:

Probably sensible!  I haven't tried the low fuel experiment on the Mk4 yet, but tried it on my old diesel Mk1 once - Drove 100 more miles on the last flashing fuel-gauge block before I chickened out and dived into a petrol station  

I know the Mk1 diesel is a smegging efficient car, but Toyota must be really conservative with the reserve fuel!!

I tend to refuel my Mk4 with around a quarter tank left and that usually takes ~26 litres, so there's still 10 in the tank in theory!! (Still can't believe I can get 400 miles out of 26 litres of petrol, esp. with the way I drive - It's madness!  )

Do the same of refuelling when quarter is left. Will see how much ch i can fill in. 

[TonyHSD]

With hybrids best not to try your luck and let the engine run dry on fuel, this can easily lead to full discharge of the traction Battery and then not possible to restart the car after you fill up with fuel. Best to refill when gauge goes down to 1/3 of its range. 

[preperationlaunch]

The car will still cut out Battery assist once the Battery falls below a certain threshold. There's still enough juice left to start the engine at that stage usually, but you'll need to reset the computers by disconnecting the Battery and add enough fuel to let it start. If you keep resetting it and trying it in that state, there's where you're really liable to have battery issues.

On the mk3, the fuel gauge reads empty when there's another 6 litres left in the tank, the remaining range is quite conservative and doesn't seem to count those 6 litres to try and discourage you from getting stuck like the above.

[Cowgirl]

I got to 44 miles left and low fuel indicator still not on…but I chickened out and filled up

[Roy124]

1 hour ago, Cowgirl said:

I got to 44 miles left and low fuel indicator still not on…but I chickened out and filled up

I have a gripe with my Corolla, watching the distance to go and fuel gauge, the fuel low light comes on. 

The problem is the fuel low caption replaces the distance to go. 

[Dala]

according to the manual, the MK4 should have a tank volume of 36l
when reporting: range 0 km - refuel immediately! - I refueled in the tank max. 28 l
At my average consumption of 4l / 100km (70.6 MPG), this means that if the car reports "range 0", the actual range is 200 km 

[Stopeter44]

On 3/30/2022 at 9:38 PM, Cyker said:

I tend to refuel my Mk4 with around a quarter tank left and that usually takes ~26 litres, so there's still 10 in the tank in theory!! (Still can't believe I can get 400 miles out of 26 litres of petrol, esp. with the way I drive - It's madness!  )

I went down to 1 bar, with My T saying I had about 15% of a full tank left, which would be 5 litres (~1 gall), but I couldn't get more than ~26 litres in (26,5 in fact), range remaining said 89 km, but if the average fuel consumption is to believed that means nearly 200 km before bone dry !