Hi

So recently my ford fiesta ecoboosts MPG has been dropping. Its went from approx 42.4 to now sitting at 39.6 . Really dont know whats up with it.

If anyone has any idea why itd do this?

Is it maybe needing serviced?

Thanks !

Cold weather?

As keiran says could be cold weather, the air is thinner this time of year so the car will be performing better

Its the cold weather. My 1.6 goes from approx 36 during the summer down to below 30 in the winter. Seen it as low as 27 when really cold :(

I know with diesel we get a double wammy of poorer fuel consumption due to the fact that it takes longer to get the engine up to temp, plus they tweak the blend of the diesel to stop gelling at lower winter temps. I am guessing that for you its the time taken to get up to temperature plus the additional engine load when using heated windows, lights and the blower settings. Not sure what the summer MPG will be on my 1.4 tdci but its currently on around 60mpg, thinking it should increase to mid to high 60s in the summer.

Glad to see I'm not the only one with a 1.6 that has astronomical fuel use, got mine down to 31.8 at the moment. 297 miles off a full tank of Vpower,

My 1.0 140 was averaging about 44mpg over the warmer months but its now dropped down to 38-39 which is pretty pants !

But I only do very short start stop journeys and can't help but drive it nippily some times :)

So all in all its not to bad I suppose - I've had faster cars (Leon FR 2.0) that won't reach 30 mpg when its cold..

Consider all of yourselves lucky. My last fill up worked out at 25MPG.

And the next will probably be even worse as it has got colder since, lol.

Cold weather makes the biggest difference on short journeys as you never get the car up to temp so it uses a ton more fuel.

I've been sacrificing using the blowers on short journeys to allow the engine to warm up more, lol.

The weather makes sense! thanks guys!!

So recently my ford fiesta ecoboosts MPG has been dropping. Its went from approx 42.4 to now sitting at 39.6 . Really dont know whats up with it.

That could be natural variation of the petrol.

The specific gravity of petrol has a legally permitted variation of +/-4%. Petrol is not actually octane (C8) but a blend of C3 to C15 so it is a product of natural and refining variations. But the calorific value remains constant by weight and the ECU maintains mass flow to the engine by adjusting the volume flow. The problem is that consumer measurements are done by volume.

David73

''The specific gravity of petrol has a legally permitted variation of +/-4%. Petrol is not actually octane (C8) but a blend of C3 to C15 so it is a product of natural and refining variations. But the calorific value remains constant by weight and the ECU maintains mass flow to the engine by adjusting the volume flow. The problem is that consumer measurements are done by volume''.

That cleared that up 😗