Filling up the Corolla, very different amunts

[nielshm]

Are the fuelgage inaccurate, or do fuelpumps have different measuments with the same amount of fuel?

I always fill up with the same reading on the dashboard. That is between 0 and 20 km. indicated range left.  With 0 km. left, is"s around 38.6 liters to fill to the brim.

How ever, some times I visit gas stations with much higher readings. The 'record' is 41 liters with 0 km. range left. 

Last week I did fill up a bit early, 50 km. range left, and the fuel light was off. 39 liters went in, and I just get a little suspicious. Do I get cheated by the fuel company, or is my fuel gage really that inaccurate?

Your experiences?

[AndrueC]

It'll be the way your car is calculating distance remaining. It turns out that measuring fuel flow is surprisingly difficult and domestic vehicles typically do so by noting how long each injector is open and how frequently.

This makes the distance remaining gauge quite inaccurate at times. The fuel consumption figure on mine is typically 5% understated when compared with the corresponding pump-to-pump measurement. But I've had instances when it was horribly wrong. In the particular the pattern of a long journey followed by a bit of local running over several days can produce some crazy good figures from my Corolla. When on holiday on several occasions I've filled up with the car saying over 70mpg but when the pump clicks off it turns out to be mid 60s.

But we also have to figure in the variations in pumps and weather. I nearly always fill up when at home from the same pump but of course can't do that when away from home. And the temperature will effect how much fuel you can get in the tank due to thermal expansion.

The bottom line is you should always take the distance remaining and fuel consumption figures with a grain of salt. They aren't usually wildly wrong but they are both far from precise.

[nielshm]

The fuel warning light turns on with 40 to 45 km. remaining, no matter the driving conditions.

I'm not sure if the warning light is triggered by a sensor within the fuel tank, or if it's a calculated value from the computer. 

Since the fuel tank only holds 43 liters, it seems like a narrow gap to put 39 liters in, without the warning light beeing activated. 

[TonyHSD]

Perhaps the petrol station pumps stopped differently. One of my last fill ups the total range was 495 miles , two days later same garage same pump only 458 miles, I was driving same places and most variables were very similar. I believe the pump simply clicked earlier. 60mpg averaged real world currently. 

[Cyker]

You've only mentioned the range reading, but not the fuel gauge reading - Has the fuel gauge reading been the same all those times?

I don't think you can gauge the accuracy of the fuel gauge if you're using the range meter to determine when to refuel - It's only an estimated range, and will vary wildly depending on how you're driving; Mine has a swing of maybe 50 miles depending on how I've been driving recently!

 

[TonyHSD]

20 minutes ago, Cyker said:

You've only mentioned the range reading, but not the fuel gauge reading - Has the fuel gauge reading been the same all those times?

I don't think you can gauge the accuracy of the fuel gauge if you're using the range meter to determine when to refuel - It's only an estimated range, and will vary wildly depending on how you're driving; Mine has a swing of maybe 50 miles depending on how I've been driving recently!

 

Gauge shows full each time while there is slightly less fuel in, I believe it’s from the pump stops.
Even it will depend how you position the gun into the neck, I did an odd type , a bit higher up and clicked earlier imo. 
The average mpg on what usually is based the estimate new range after fill up was very similar to the previous fill up by the dashboard and calculated from the fuel quantity. The first fill up 60.1mpg , range 495 miles, the second fill up 59.7mpg range 458 miles, I am sure it’s from the pump, perhaps a litre less petrol and we have the difference. 

[Cyker]

Sorry my query was directed at the OP - I thought I quoted them but apparently didn't!

They keep questioning the accuracy of the fuel gauge, but only talk about the range aka guess-o-meter readings, and that they're basing their refuel timing based purely on that - To me that would explain why they're putting in such varying amounts of fuel, since the range remaining has only a vague relation on the amount of fuel left!

 

[nielshm]

It's well known, that Toyota is very conservative in terms of going to the limit.

The last 20 years, fuel reserve has been between 7 or 8 liters, no matter the model. 9 of 10 refills is 36.5 liters, if I do it when the warning light turns on.

I allways fill to the brim, and don't use 1. or 2. click method. 

[Cyker]

Be careful with that depending on your country - Literally brimming it, so you can see the fuel in the filler neck, can damage the evap system, esp. if there is a charcoal fuel vapour filter in it, as fuel can get into that and ruin it!

 

[AndrueC]

A simpler and safer strategy is to start thinking about filling up when your tank drops below half. There's little to nothing to be gained by running the tank nearly dry and in fact several good reasons not to do that.

[TonyHSD]

That’s right , as someone said recently fill up when half and it feels like you have a full tank petrol for half price 😂😉 For  the evap system and refill to the brim been proof it’s only a myth and I personally done it few times no problems at all, just not nice to have petrol coming out of the neck and spills on the car and on the ground. 

[Cyker]

I don't think we have that evap system requirement in the UK so you're right there, but I don't know what country the OP is from so just putting the warning out - I know people in the USA, where they do have charcoal evap systems, who've made this expensive mistake!

I couldn't do half a tank as it feels like I haven't driven anywhere, and I feel silly when I go to fuel up and can only put 20 seconds worth in   But a quarter is enough - That's still over a hundred miles so no range anxiety but still a good fill amount!

 

[bigblock]

On 7/23/2023 at 5:46 PM, AndrueC said:

A simpler and safer strategy is to start thinking about filling up when your tank drops below half. There's little to nothing to be gained by running the tank nearly dry and in fact several good reasons not to do that.

I always think about filling up when just below half a tank left as well. This is also means less pain in the wallet when the price goes up.

[Cyker]

I just filled! 420 miles covered, only got in 24 litres!