Wind typically blows from the west or south west, be interesting to see if the journey north east led to worse economy with a stiff nor'easterly breeze against you all the way.

Wind factor has a big influence, you don't notice it so much physically in a modern car but you certainly do in a truck (think back to cycling), even something as relatively streamlined as the tanker i drive if i have a following wind progress is noticeably faster and easier for less use of the throttle.

Edited by gordonbennet on 16/12/2022 at 07:49

I don't know how to link to a previous post but this is in answer to Falkirk Bairn

I just use the trip computer in both. I realise they probably aren't very accurate but but I assume they're similarly inaccurate for both journeys.

The Peugeot being more economical than the Fiat is a brim to brim calculation.

Edited by nico77 on 16/12/2022 at 09:21

We drive to Scotland twice a year, its about 430 miles door to door. Almost always we get better mpg going north than coming home south, just a couple of mpg. Simple really, the prevailing winds are from the south west which helps to run north.

How you drive while the car is warming up can also make quite a big difference. If the first 3 miles of the journey in one direction is in stop-start traffic, and the other way is straight onto a fast road, the engine will warm up quicker on the latter and then use less fuel overall.

I suspect reason will be wind though. It does make a big difference to motorway MPG - in strong winds I've had as much as 15mpg less in fairly boxy cars when going into strong wind as I'd get in still conditions. Not surprising really if you think when driving into a 30mph wind the car is going through air doing over 100mph rather than 70 so does closer to the economy of a car doing 100. It all evens out though as in the other direction you can get the fuel economy of doing 40mph when you're doing 70.