Suspect faulty fuel gauge

[Haliotis]

I think my C-HR fuel gauge is not working.  I last filled up - until pump switched off, so full - on 21 June 2024.  Since then I  must have covered about 100 miles.  For a few days I noticed that my gauge needle had not moved below about 2mm from the full mark.  Today I took it into the Toyota dealership where they did a diagnostic check and found nothing wrong.  During my journey from Wigston, Leicestershire to the Nuneaton dealership, I did notice that the gauge needle had dropped about another 2 mm but it seemed to have crept UP slightly after my journey back home.  I used the M69 for a large part of the journey, in both outward and homeward directions.  When I switched the engine off back home, the mfd indicated a fuel consumption of 75 mpg.

When I visit family in Burbage (usually once a week), I also use the M69 for these trips.    On leaving, this is after 11:00pm at night, and my trip always shows an mpg in the low sixties, so 75 mpg during busy daytime hours sounds unrealistic.

Based on experience, I believe I can safely go another week without running out of fuel.  I will then visit the fuel station, take a picture of the fuel gauge on my camera, then fill up and see how many litres of fuel have been accepted.   Can’t think of anything else to do at this point in time.

[Corollanutter]

Is this a new experience on a car you have had for a while?

Normally the gauge on my Corolla only drops to the "Full" mark after 80-90 miles after a fill. I'm only filling it to cut-off. However once the gauge hits the full mark it starts to drop fairly rapidly in line with the mileage done. 

You need to put some more miles on it to get a true picture.

[Haliotis]

49 minutes ago, Corollanutter said:

Is this a new experience on a car you have had for a while?

Normally the gauge on my Corolla only drops to the "Full" mark after 80-90 miles after a fill. I'm only filling it to cut-off. However once the gauge hits the full mark it starts to drop fairly rapidly in line with the mileage done. 

You need to put some more miles on it to get a true picture.

I’ve had the car since April 2023, and this is the first time I have had reason to feel something is wrong.  To be honest, my practice is to refill the tank when it’s reading about half full, then fill up until the pump cuts out.  Other than that, I don’t really look regularly at the fuel gauge beyond occasional glances, but I sense the different behaviour from probably subconscious observations and, Chris, your comments “feel” familiar.  I think (hope?) my previously suggested course of action should give results one way or the other.

[Bper]

Hi Albert, I often check my fuel gauge after a long drive and usually notice little to no change in the needle position, which sometimes makes me think I might be driving a hybrid 😂. However, after a couple of short trips, the gauge suddenly drops down 😭.From what I've read, there are several possible reasons for this. Fuel movement in the tank during driving especially during turns, braking, or on uneven road can cause temporary fluctuations in the gauge. 

Additionally, the sensitivity of the fuel sender unit, which measures fuel level, can be affected by the car's tilt or movement.Temperature also plays a role fuel expands in heat and contracts in cold, which can slightly alter the gauge reading. Modern gauges often exhibit non linear behavior, showing full for longer after refueling and then dropping faster in the second half of the tank.These factors together can lead to normal, temporary fluctuations in the fuel gauge reading.

As you have had it checked by Toyota it should be fine but it doesn't hurt to keep an eye on it.

[Haliotis]

Hi Bob, the fuel will swill about a bit while the car is on the move, but I never need to check it at those times because I fill up at half full.  I only check the level when on my drive, which is fairly level so gives a satisfactorily correct reading.

But I will be watching it, and do the checks I have mentioned when the level has dropped enough to fill up again.

[Cyker]

It's probably normal; My other Yarisuseseiesiuseses behaved similarly - It's why I joke about the accuracy of the fuel gauge sometimes  

I think it's partly due to the shape of the tank, but also the long polling interval of the fuel level. At certain levels, it becomes more sensitive to gradients which can make it read low then go up again when the car is turned off and on again.

[Haliotis]

Not only the shape of the tank and angle of car from level, if the sender solenoid has an arm between solenoid and float, then the arc of the arm will vary as the level of the fuel surface varies.   I am not familiar with how the sender units of modern cars might differ in design, but from past experience I would imagine that car makers expect drivers to fill up when the gauge indicates towards the lower end of the scale, and not rely on the accuracy of the gauge and go on the drive when the gauge needle is in the red/reserve position.

From my experiences of caravanning, when on occasion we have been redirected onto devious routes because of such things as an RTC or other reasons, I have always ensured that I have more than ample fuel for my journey (the last thing you want is to run out of fuel with a caravan hooked on the back), and this habit has remained with me.   The last thing I want is to run out due to a wildly inaccurate (faulty) fuel gauge; which could happen late at night in a lonely, hazardous or unsafe area.

I don’t know how far one could expect to travel using only the hybrid Battery power.  So far, keeping my energy use diagram on the screen, the car appears to draw power from the Battery even when it is only halfway charged, and when I am cruising at 60mph on the motorway with the cruise control engaged.  This makes me wonder if the Battery gets anywhere near to fully charged.  Or should this visual diagram of the battery cells’ storage situation also be regarded as a very rough guide? 

[Cyker]

Yeah, that's partly why I always refuel around a quarter tank/100 miles remaining, which is also a big reason why current EVs just don't do anything for me since that's over half their range most of the time (That and they're all fat bloated SUVs with the footprint of a van or worse...! When they can make them as long-ranged and nippy as a Yaris then I'll be more interested...)

[Haliotis]

Full EVs generally have very quick acceleration.  But I would not have one - I don’t think the charging infrastructure is anywhere near sufficient to meet the eventual demand, and may not ever reach it.   I like the advantage of the ICE back up of the hybrid.

[Cyker]

I like the idea of being able to charge an EV at home and always having 500+ miles of range without ever having to go to a petrol pump.

Of course this depends on a) Someone inventing an EV that can actually do 500+ miles in something the size of a Yaris, and b) Me ever getting my own house (Which is currently a virtual impossibility unless I move so far away from London it takes me hours to commute in, which ironically will necessitate an EV with even more range...!)

 

[Rhymes with Paris]

15 minutes ago, Cyker said:

Me ever getting my own house (Which is currently a virtual impossibility unless I move so far away from London it takes me hours to commute in, which ironically will necessitate an EV with even more range...!)

Come Oop here Cyker, the houses are relatively cheap, and it's only 2 hours from London, well at 3 in the morning it is.

I once drove from here down to Dover through London in a bit over 3 hours in that diesel Citroen I had, mind you in those days it was scaffold planks tied with baling twine onto the ferry.

As regards ev charging points , the guy who used to light the gas mantles in the street lamps only retired last year.

[TonyHSD]

The fuel gauge behaviours it’s just about right. These rarely goes wrong. 
What other reason to offset range can be car been kept in ready mode for diagnostic or other similar maintenance purposes and engine been running for some time, the rest all been mentioned above. 
For the evs problems, it’s not the charging or anything else except the Battery weight and sustainability, the only major problem in those is Battery. 
Aa, one more and also major problem is the size and the price of most Bev.