High Fuel Consumption after service

[NowhereMan]

Hi everyone. Just joined. Apologies of this topic has been discussed before. yesterday had my 2014 Toyota Aygo (1.0L) serviced at a local garage where I work. The service included replacement of front brake discs and pads, 3 spark plugs, air & pollen filters, oil filter and oil. My commute to work is 20 miles. Normally, from Monday to Friday, with a full tank, I use up 3 bars worth of fuel. After the service yesterday however, I used up 2 bars on the way home - and another 2 bars on the way in to work this morning! There's no smell of petrol and the car drives smoothly. My first reaction is to take it straight back to the garage. But just wanted to check here in case anyone has experienced anything like this before - or if I'm overlooking something. Thank you

[FROSTYBALLS]

How many litres did you fill it up by?

[NowhereMan]

2 minutes ago, FROSTYBALLS said:

How many litres did you fill it up by?

I filled it up with 21 Litres yesterday morning before dropping it off at the garage - and that showed full number of bars. 

[TonyHSD]

Hi, 

you will need to check consumption brim to brim method first to see if really has increased and by how much. We are now heading into colder weather, temperatures dropping 10C° overnight and this significantly decrease fuel consumption., plus high winds and wet roads this can increase consumption by 5-10 mpg easily. Best to check and adjust tyres pressure in the morning before driving off. , under inflated tyres can cause higher fuel consumption rise than wrong type of oil for example. If the service is done with parts as per the specs then I doubt it it’s from the service itself. Best to do all checks yourself first bit if you unsure you can always speak with the technician who worked on the car for double check his work or to give you his opinion. 
Good luck 👍

[Goinker]

Also don't forget that garages are supplying E10 petrol now which does have some detrimental effect on your MPG as the engine will use slightly more fuel for the same power and mileage due to the less volatile increased Ethanol content.

                                                                          Keith.

[NowhereMan]

Thank you everyone for your input. I've checked tyre pressures earlier today - all good. On the way home this evening I'll top up with petrol (brim to brim test) - and see how I get on. After the drive home, I'll check the tyres for temperature - in case the new brake discs/pads are causing excessive friction. Maybe good I didn't just burst into the garage today to complain - better to go armed with more data!

[Devon Aygo]

What oil grade did they use, grades thicker than 0w20 e.g. 5w30 will have a detrimental affect on Petrol consumption.

[NowhereMan]

UPDATE: I filled up the tank with petrol (until nozzle clicked off) just before heading home yesterday. It equated to  just 16.4L - which immediately told me that the 2 bars indicated by the fuel gauge must be wrong. When I turned the car on, it displayed the full number of bars! No bars were lost on the journey home (20 miles) and none on the journey in this morning (with my commute, I normally lose one bar every 2 days). The front tyres were not hot - in fact, I could even touch the brake discs - they were slightly warm but nothing more. No smell of burning rubber or hot metal. So I'm not sure why I panicked yesterday - probably observed an anomaly as a result of the colder temperature and because of the service the day before,  just got it into my head that something must be wrong. Apologies all round - false alarm.  

[Catlover]

You cannot do mpg calculations from reading bars on a fuel gauge, absolutely 100% no. A fuel gauge is not sofisticated enough. And when you do brim to brim, the more miles you do the more accurate it is going to be.        
If the brakes had been binding, checking the heat of the brake callipers/disc is the best way, but be careful, if binding then they can be very hot. Best to check the centre of the wheel first. Tyre heat will tell you nothing.

[haelewyn]

I read through all posts but thought about one advice from when i read the original post.

I was thinking of telling you to check if the brake work didn't cause sticky brakes.. but i guess that is what you guys in UK call 'binding breaks'.

My idea was, even more simple than to feel for heat on the wheel : 
Just let your car roll out on any safe road. See if it behaves normal, keeps on running long enough when you let it go at 6 mph or so.
Switch off the radio and listen for brake sounds that should not be there if your foot is not on the brakes.

If that goes all right and your car doesn't come to a complete stop faster as it should, everything is ok.

And indeed : the fuel gauge should not be considered as an exact measuring device. Rather some tool giving you an indication. Nothing more than that.

I know the TS doesn't need this advice any more but maybe one day somebody else will benefit from it.

[NGRhodes]

20 hours ago, Devon Aygo said:

What oil grade did they use, grades thicker than 0w20 e.g. 5w30 will have a detrimental affect on Petrol consumption.

Only by a couple of %, its part of the ACEA specs of European oils. For the purposes of this conversation the difference is negligible.
In real world use that % is below the error of reproducibility on real roads using built in car gauges and other variables such as wind, temperature, tyre pressures etc.

[NowhereMan]

19 minutes ago, haelewyn said:

I read through all posts but thought about one advice from when i read the original post.

I was thinking of telling you to check if the brake work didn't cause sticky brakes.. but i guess that is what you guys in UK call 'binding breaks'.

My idea was, even more simple than to feel for heat on the wheel : 
Just let your car roll out on any safe road. See if it behaves normal, keeps on running long enough when you let it go at 6 mph or so.
Switch off the radio and listen for brake sounds that should not be there if your foot is not on the brakes.

If that goes all right and your car doesn't come to a complete stop faster as it should, everything is ok.

And indeed : the fuel gauge should not be considered as an exact measuring device. Rather some tool giving you an indication. Nothing more than that.

I know the TS doesn't need this advice any more but maybe one day somebody else will benefit from it.

Thank you for the suggestion. Just performed this test now in our staff car park.  We have a generous 50m length driveway from the main entrance to the parking spaces. This is conveniently inclined by 7 degrees.  I stopped at the top of the incline, applied the handbrake, put the car in neutral - then took off the handbrake - and the car promptly rolled forwards (accelerating gradually) without anything appearing to grip or hinder motion - all the way to my usual parking spot! I think for now I'm satisfied that all is well (but will keep an eye/ear open over the next few days). I understand also that the digital fuel bar indicator on the dash is not an accurate measure of the actual volume of fuel in the tank at any given time. 👍

[Guest]

4 hours ago, NowhereMan said:

 I understand also that the digital fuel bar indicator on the dash is not an accurate measure of the actual volume of fuel in the tank at any given time. 👍

... and is also very non-linear, the less fuel there is in the tank the fewer miles each bar indicates - for example I get around 100 miles for the 6th bar but only around 40 miles for the 2nd bar (and something in between for the 5th to 3rd bars).

[Cyker]

Yeah this seems to be a weird thing with Toyotas - My Mk2 was particularly bad! Could do 300 miles on the first half of the fuel gauge, but only 80 on the last half! You'd think Toyota would have learned to code some compensation into the gauge to compensate for the V-shape of their tank by then!

Thankfully the Mk4 isn't so bad - It's still not linear, but it's about as inaccurate as my old diesel Mk1 was. Still does more miles on the first half, but nowhere nearly as badly skewed as it was on the Mk2!!

 

 

[Vandals01]

Aygo is one of the most difficult car to fill-up as it will set off the petrol hose trigger at anytime without the tank being full.

To avoid this, someone suggested point the hose side-way when filling, which seems to work on my Aygo.

As for E10, I found my MPG dropped from 59-60 MPG to 57-58 MPG (using BP unleaded 95).  So honestly not that significant.

For switching from 5w30 to 0w20.  There are no visible difference in terms of fuel consumption.  Although 0w20 does seems to start-up easier.

[Guest]

11 hours ago, Cyker said:

Yeah this seems to be a weird thing with Toyotas - My Mk2 was particularly bad! Could do 300 miles on the first half of the fuel gauge, but only 80 on the last half! You'd think Toyota would have learned to code some compensation into the gauge to compensate for the V-shape of their tank by then!

Thankfully the Mk4 isn't so bad - It's still not linear, but it's about as inaccurate as my old diesel Mk1 was. Still does more miles on the first half, but nowhere nearly as badly skewed as it was on the Mk2!!

It's not just a Toyota thing for the gauge to be non-linear, every VAG vehicle I owned between 1999 and 2021 had exactly the same 'feature' where you could go at least twice as far on the half-full to full section of the gauge as on the empty to half-full section.

It's caused by the tank not being rectangular but shaped to fit around the suspension, exhaust, etc. and car manufacturers don't see the need to compensate for the non-linearity in the instrument cluster firmware (remember in the olden days there was no firmware so there was no easy way to compensate).

[haelewyn]

6 minutes ago, PetrolDave said:

remember in the olden days there was no firmware so there was no easy way to compensate.

If they really wanted they could have painted the lines differently perhaps... that's a simple firmware solution 😁

[haelewyn]

Does anybody have an idea about the difference of the car's measured fuel consumption (on board computer) and the real fuel consumption ?

Does this system lie a lot ?

[Dave the aygo]

I have noticed a drop in mpg since I started to use e10 fuel 

[Guest]

11 hours ago, Dave the aygo said:

I have noticed a drop in mpg since I started to use e10 fuel 

How much of a drop?

The lower calorific value of the extra added ethanol means a small (about 2%) drop would not be unexpected.

Remember too that the colder weather now means the engine warms up slower so will stay in the warm-up phase longer and hence use more fuel.