C5 Aircross 2025 1.5 HDi auto. Run out model (not the new one)with only 100 miles on it. Economy and gearbox concerns.

[Van Rouge]

I've a new C5 1.5 HDI Auto, and am noticing issues with fuel economy and the gearbox with 20- 35 mph low speed driving .

In normal mixed driving it averaged around 51- 52 mpg which is about what I expected and in line with my old 308 150 Hdi manual.

Using the auto box even in eco on my regular commute with stop start working fine, it's barely getting 33 mpg. The old car on exactly the same route was getting around 42.

That's appalling for a diesel.

The gearbox always sounds like it's at least one or two gears below the one it should be in, almost like the gearbox software thinks it's got a lower torque petrol engine.

If I do the same journey using the auto box manually using the diesels torque it's much better 39-40 mpg. Which for a heavier car with a smaller capacity diesel seems ok, and may improve as it loosens up with age.

In fully auto even the slightest press of the accelerator causes it to drop a gear, unnecessarily, as there's more than enough torque. 5th gear at less than 30 is doable.

Does anyone think there is something wrong with this cars gearbox software or are they all like this?

I've driven diesel cars for over 30 years, and this one just doesn't seem right
Thanks.

[wheeler]

Its still under warranty, take it to a dealer & they can check if there are any software updates for the engine & gearbox.

[PaulC5]

We have the 1.5 hdi in our 308sw (manual gear box) and its fuel economy is worse than I would have expected, especially compared to our previous 1.6 hdi cars. On a long 180 mile run at speed limits to the Lake District our last C4 would give 60 to 70 mpg but the 308 is 55 ish. We also have an Octavia with a 1.5 petrol and that is giving 60 mpg on the same trips so not too impressed with the 1.5 hdi economy.

Gear wise the 308 needs to be up to 40 mph for changing to 5th and nearer 50 mph for 6th. Letting it struggle at lower speeds in too high a gear is probably not good, especially in our case where it still has the 7 mm cam shaft chain. When you are running in a new engine I think it is not recommended to labour it.