2017 CDTI Zafira very poor fuel economy

AdrianC

The dealer can, at least, check for things like binding brakes and any fault codes - including DPF issues that might be using fuel to try and force a regeneration.

onomatopoeia99

rumblefish wrote: »

The car is doing roughly 300 miles for around £50 of diesel - although obviously this is approximate. The driving is pretty mixed but I'd say it leans toward more duel-carriageway driving.

Length of the journeys (time and distance)? Free flowing or stop-start?

At this time of year you will see an mpg reduction and unless your journeys are mostly over half an hour it can be quite significant. My car is petrol and my commute 10 miles / 20-25 minutes, which I do outside rush hour to avoid queues and I can see as much as a 20% reduction in the mileage I get from a tank going from summer to winter.

System

If it has a rev counter when are you changing gear? My wife drives a petrol car so when she drives my diesel Mondeo she revs it a lot higher before changing gear. End result is I can always tell when she has driven it by how much the average MPG has dropped on the trip computer. Try to change no higher than 2500 or so RPM, put it in a gear where you're cruising in free flowing traffic around 2000RPM or slightly lower.


Also we're now on winter mix diesel and you can see roughly a 10% drop in fuel economy.

rumblefish

AdrianC wrote: »

The dealer can, at least, check for things like binding brakes and any fault codes - including DPF issues that might be using fuel to try and force a regeneration.

Much appreciated, I think I'll try and get this looked into!

rumblefish

In answer to the driving type - the car is used through the week for commuting which involves driving on a busy dual-carriageway and then a busier stretch into work. Probably similar coming home although due to a mixture of shifts starting anywhere from 6AM to 4PM this will often be done outside rush-hour.

On the weekends the car is used for more family-based activities like a trip to the beach to walk the dog.

The car certainly isn't driven 'enthusiastically' in any respect being a diesel people carrier!

danny91

It could be that the car is trying to do a DPF regen, but the car is getting switched off before it has chance to finish, therefore its trying to complete a regen every time it is started.

DoaM

I have an Insignia Grand Sport with a 1.6 diesel engine (136PS version), and I probably have a similar commute and usage as you do. (Approx 13k miles per year).

My average fuel consumption (between Nov 17 and Mar 18) was 48 mpg. (Lowest was 45, highest was 51).

Current average consumption for Nov 18 is 46 mpg.

(Consumption figures calculated fill-to-fill and not based on the trip computer calcs, albeit my trip computer results tend to be quite close to my own calcs).

facade

Don't forget "Winter diesel" has a lower calorific value than "Summer diesel", and you always get less mpg. I would think the garages have switched by now even though it isn't Winter yet..

DoaM

TBH I'd never heard of "winter" and "summer" diesel before, but it makes sense. Presumably the additives to prevent "gelling" of the fuel reduce the calorific value. (Or the fact that there are additives decreases the amount diesel fuel per unit volume hence the calorific value drops accordingly).

My Apr 18 to Oct 18 average was 52 mpg. (Lowest 47, highest 55).