Hi folks,

I would appreciate feedback on what I have seen.

I have just bought the car. It is a great drive, but...

It seems that you could run out of fuel based on what is being displayed, which is off for a very modern car.

I drove the car at a steady 55mph, very gentle acceleration throughout, and noted the following.

Does this seem accurate? Re-filling the tank at 300 miles seemed to confirm the mpg figure.

Distance = 0 , Reported range=750 miles, Fuel tank=full, Fuel gauge=full

Distance = 211miles, Speed=55mph (no hills), Reported range=830miles, Fuel Gauge=full

Distance = 292miles, Speed=55mph (few hills), Reported range=715miles, Fuel Gauge=dropped one notch

The live mpg seems slow to update (even when going uphill).

The fuel still showed full at 211 miles and dropped by one at 292 miles.

The range showed 712miles at 292 miles, but calculations based on fuel used and mpg show 549 miles.

Calculations:

Distance = 292 miles, filled tank with 22.9l => mpg = 292 / ( 22.9/4.54609) = 58mpg

Distance = 292miles => Range = [ (66l - 22.9l) / 4.54609 ] x 58mpg = 549 miles

So the mpg looks accurate but the reported range is off by a lot.

The fuel tank needs 22l but the fuel gauge is only down by one notch.

So on that basis, you could run out of fuel based on what is being displayed, which is off for a very modern car.

cheers

CT

Hello, welcome to the forum.

While it is usually the case that the fuel gauge remains at 'full' indication for 50 to 70 miles after completely filling the tank, it would appear unusual to me for it to stay there for more than 200 miles!

Is your tank capacity 60 litres on the Superb?

I'd consider carrying spare fuel in a decent can and try running the tank down further to check whether the gauge and range computations start to agree.

Is your tank capacity 60 litres on the Superb?

I am assuming that it is 66l .

I'd consider carrying spare fuel in a decent can and try running the tank down further to check whether the gauge and range computations start to agree.

The car is Skoda approved and still under warranty, so I can have it looked at. I am interested in any and all opinions.

The instantaneous mpg was showing 70mpg+ on flat sections of motorway.

It's not clear how the range calculation is made. If the fuel tank sensor is off then that may explain the range reporting.

If driving and actually getting 60 mpg (4.546 litres) and the reserve message came on showing 60 miles you might well get 70 miles even 80, or if your driving style changes or you then need to climb lots before the filling station maybe only 50 miles.

No need to run out of fuel in the UK is there unless north of Inverness during the festive season.

Edited 29 October, 202529 Oct by Evolution13

33 minutes ago, Evolution13 said:

If driving and actually getting 60 mpg (4.546 litres) and the reserve message came on showing 60 miles you might well get 70 miles even 80, or if your driving style changes or you then need to climb lots before the filling station maybe only 50 miles.

No need to run out of fuel in the UK is there unless north of Inverness during the festive season.

... Unless the fuel gauge and range computation errors continue until the tank is actually empty.

There is that right enough.

So best the OP does the running low when not in the far flung regions of the UK and gets that Fuel can and funnel and fills it up.

43 minutes ago, ctoul said:

Is your tank capacity 60 litres on the Superb?

I am assuming that it is 66l .

I'd consider carrying spare fuel in a decent can and try running the tank down further to check whether the gauge and range computations start to agree.

The car is Skoda approved and still under warranty, so I can have it looked at. I am interested in any and all opinions.

The instantaneous mpg was showing 70mpg+ on flat sections of motorway.

It's not clear how the range calculation is made. If the fuel tank sensor is off then that may explain the range reporting.

AFAIK, the fuel usage computations are made either from fuel pump-stroke data or sensors in the fuel delivery line - I presume range is calculated from measured tank contents (tank sensor) divided by current usage rate.

No need to run out of fuel in the UK is there unless north of Inverness during the festive season.

Which is not unusual for me(!)

AFAIK, the fuel usage computations are made either from fuel pump-stroke data or sensors in the fuel delivery line - I presume range is calculated from measured tank contents (tank sensor) divided by current usage rate.

I think that is the key point. If the tank sensor is faulty/inaccurate then that would explain "full" after 200 miles and an error in expected range at that point.

After ~300 miles I needed 22.9l to fill up - a third of a tank - so 200 miles should be 1/4 of a tank used, which should register.

Thoughts?

I agree that a faulty or insensitive tank sensor could be an issue - recommend a few more fills of the tank to see if the apparent errors continue, running the tank well down - with the back up of spare fuel just in case.

@ctoul Are you brimming the tank, or even 'Venting it'. Or do you stop filling after a couple of cut outs of the petrol pump?

Venting a Fabia Mk2 vRS which had a 'Vent' Slide could get an extra 7 litres in to the tank.

Handy for Oop North when wanting in as much Super Unleaded as i could, and not intending parking up before maybe 50 miles covered.

If the tank is fitted with a carbon breather canister, doing this is not recommended - recommendation is to stop pumping on 'First Click' of nozzle shut-off.

No I was not "overfilling" the tank.

I believe the official tank capacity is 66 litres but I've put 71 litres in on one refill, that was pretty much right to the brim, but as I cover quite a few miles it doesn't stay brimmed for long. Mine can do up to 225 miles before the fuel gauge moves when driven carefully, I average 60mpg, mainly motorway cruising.

The range after brimming is often lower than when it's been driven for a few hundred miles, the 'since refuel' plus the remaining mileage shows a greater range than when brimmed.

Has there been any improvement on your fuel computations? @ctoul

Hello, not so far. I am running the tank right down to see whether it makes any difference.