My car has recently come back from its 3rd year fixed service and the petrol consumption has gone down about 13% on the trip computer. I drive very conservatively, a 34 mile trip over the weekend along mainly dual carriage way and country roads - max speed 60 recorded 38mpg whereas normally it would be around 44mpg. Any ideas what might have gone wrong - it was ok before it went into service.

Also I've noticed the oil used this time seems to be different - last time it was 5W-30 this time 10W-40 has been put in - would this have any bearing?

Thanks

the ecu was probably reset on the service, give it 100-200 miles and see how it is then once the ecu has re learnt your driving style.

Also I've noticed the oil used this time seems to be different - last time it was 5W-30 this time 10W-40 has been put in - would this have any bearing?

Thanks

Effectively, a thicker viscosity oil could lower your mpg couldn't it?! :confused:

Effectively, a thicker viscosity oil could lower your mpg couldn't it?! :confused:

In theory, yes. But remember, the first number is the viscosity when cold, the second is the viscosity when the engine is warm, so only the second figure would be significant (unless all you do is such short trips your engine is never warm). There is more likely to be more difference in fuel ecomomy with the other (usually unrated) oil additives such as friction modifiers etc.

Pretty much same happened to me after my Octavia came back from service (change of bearing for air condition... or something like this). All of a sudden I can't get it under 6.6-6.8l/100km (sorry guys no idea how much MPG is this), while before I could easily get it around 6.0 or 6.1l/100km on same road and with pretty much same way of driving. From this what I know, oil is still same, so basically they changed only something with air condition, and worse is, that it's same even if air condition is off. So no idea what it would be really wrong.

6.6 is probably about 40mpg or higher as mine is below (mpg and l/100km)