I've notice a sudden increase in fuel consumption of my 1.4 16v engine. About 10% worse, 46 to 42mpg in rough figures.

The only change that took place after the run of good figures was tracking to sort out a tyre wear problem and fitting new tyres.

Tyre pressures are 33psi all round and i check them regularly.

No codes are showing.

 

Any Ideas ? What would cause a sudden drop? I can understand a slow deterioration from plugs or whatever.

Performance seems no different and it runs smoothly.

4 minutes ago, totoro said:

a sudden increase in fuel consumption

 

As calculated from miles driven/litres used, or as indicated by the car?

 

 

Sounds like the change of tyres then.

You could have run a tape measure around the old tyres and then the new and seen if there was any difference in the circumference.

Too late now if the tyres were left at the fitting centre.

1 hour ago, Wino said:

 

As calculated from miles driven/litres used, or as indicated by the car?

 

 

 

brim full to brim full, the figure corresponds closely with the indicated mpg at the end of a journey

 

mph indicated on speedo has stayed the same compared with satnav speed, same offset as before

Edited 4 December, 20196 yr by totoro

Probably mainly the tyre diameter change. Fewer revolutions per real mile driven, but the car doesn't know what the real miles are.

Has been quite chilly lately though, that will have an impact.  How many miles before you see 90°C on the gauge (wondering about thermostat performance)?

 

 

Edited 4 December, 20196 yr by Wino

Usually people fit new tyres to get more grip not less, unless it is a drift car.  Some put up tyre pressures to ECO pressure to reduce grip / friction which is odd!

Time will tell how the fuel consumption works out with the track set and good tyres on. 

Better safe than wealthier.

How many mpg did you get last winter? You can't compare summer with winter mpg, because the engine takes longer to warm up. You always get less mpg in winter. Also, it tends to be windier in the winter. More wind equals more drag and less mpg. Try riding a bicycle in the winter and comparing it to the summer. You always go slower riding a bicycle in the winter because of the wind.

Edited 4 December, 20196 yr by Carlston

How are you getting that? Big motorway stretches? This is the AUB engine?

9 hours ago, alff said:

How are you getting that? Big motorway stretches? This is the AUB engine?

It's the BBZ engine and I do mostly runs of about 40 to 50 miles on country roads. I do very few short trips.

On a couple of motorway trips in the summer I set out to see what it would do by driving economically, lorry speed, and got about 55mpg for one trip and 49.8 mpg between fills.