So I had the car MOT'd and an interim service (pollen filter and oil change). It needed a couple of new tyres and the front brake pads doing.

These were all done but since I got it back (in fact I noticed it as soon as I picked it up) the fuel consumption has been considerably higher going from averaging about 40MPG to 30MPG!

 

My Octavia has been really good on fuel consumption and now it's no better than the BMW 320i it replaced. The car drives OK, the performance seems just the same. There's no also an annoying buzz from the dashboard somewhere which I suspect is  some trim that's got loose.

 

When I got in I started the car I did notice that the average MPG had dropped like a stone but I assumed this was the mechanics doing the road test giving it the "beans" whilst doing this (and probably whilst the engine was cold - Grrr...).

 

The car seems fine but the fuel consumption appears to be really bad now.

 

Any ideas?

Ask if it had any software updates and exactly what oil has been used.

 

Check the oil is not overfilled.

Edited 12 December, 20187 yr by xman

Are the new pads binding?  New tyres at the correct pressure?

Calculated or computer? 

 

Having a low readout after the service doesn’t mean it’s been blasted about. Probably been idling for a while.

53 minutes ago, xman said:

Ask if it had any software updates and exactly what oil has been used.

 

Check the oil is not overfilled.

 

No software updates and the oil according to the service sheet is "Skoda 0/30W" ?

 

16 minutes ago, SC03OTT said:

Calculated or computer? 

 

Having a low readout after the service doesn’t mean it’s been blasted about. Probably been idling for a while.

 

Good point.

41 minutes ago, ords said:

Are the new pads binding?  New tyres at the correct pressure?

 

Pads don't appear to be binding as I use Eco mode all the time and the car is gliding along in Neutral as normal when I lift my foot off the throttle, without appearing to slow down any quicker than normal.
 

First thing I did when I got home was check the tyres and as usual they were all over-inflated (I'm sure they err on the safe side by putting too much in when they're not sure).

Thanks for the suggestions everyone

 

Check the tyre pressures & and wait until at least you have filled the tank fully again before starting to calculate an average again.

Its likely been idling for a while during/after the service.

 

 

Sorry I can not see what car you have.  Why 0w 30 and not 5w 30? 

 

 

2 hours ago, Offski said:

Sorry I can not see what car you have.  Why 0w 30 and not 5w 30? 

 

 

1.4TSi Octavia

Not sure why they used 0/30 perhaps they thought it would be better for the winter months and as long as it's meet the right VW specs it should be OK. I'm guessing they call Skoda oil because they get it in bulk and it could be a variety of manufacturers' oils that depending on cost are supplied but all meet the relevant spec.

It seems unrelated to sudden drop in MPG though. Thinner oil should increase the MPG (I think that's one of the motivations for the change to thinner oils these days - my old Cortina with a Pinto engine used Castrol GTX 20/50 back in the day)

The dealer I purchased mine from said they use 0w30 rather than 5w30 and provided a 0w30 top up too which meets VW 504/507 spec. Not sure why they used that rather than the more common 5w30.

@Lingnoi, cheers i know all that stuff, i was just wondering why they use 0w 30 FS LL when others have usually 5w 30 FS LL and now they should have in VW508/509 for those requiring that. So 0w 20 FS LL.

 

The others posts have covered the usual stuff.

Reset your cars, computer.

Check the tyre pressures and reset the TPMS. 

 

Be aware what was changed, was the Spark Plugs and Air Filter done, be sure to ask but then the Invoice should show that as it should the oil used.

& Always ask about Software Updates or other enhancements as not all owners get told there were updates (service campaigns) carried out.

 

PS

Winter in Hampshire or elsewhere in the UK has not required the use of 0w 30 FS LL to assist in achieving efficient running temps and economy really with TSI's.

VW Group have decided that to get what looks like good WLTP results that 0w 20 FS LL is simply clever though.

Edited 12 December, 20187 yr by Offski

2 minutes ago, Offski said:

@Lingnoi, cheers i know all that stuff, i was just wondering why they use 0w 30 FS LL when others have usually 5w 30 FS LL and now they should have in VW508/509 for those requiring that. So 0w 20 FS LL.

 

The others posts have covered the usual stuff.

Reset your cars, computer.

Check the tyre pressures and reset the TPMS. 

 

Be aware what was changed, was the Spark Plugs and Air Filter done, be sure to ask but then the Invoice should show that as it should the oil used.

& Always ask about Software Updates or other enhancements as not all owners get told there were updates (service campaigns) carried out.

 

It was an interim service so only the oil with filter, sump plug and washer, and also the pollen filter. Brake pads and tyres were necessary for the MOT and honestly the new brake pads seem worse than the old ones (I guess they'll bed in eventually) but I was surprised how much better the grip was with new tyres, should have changed them earlier (they were still legal).

Just a shame the fuel consumption's taken such a nose dive.

I'll check the actual MPG (the computer was usually fairly accurate, within 5%) when I next fill up.

You probably already know that the cold weather will reduce your Avg Mpg. My 10 mile A road commute drops from 38-40mpg to 33-34 Mpg at this time of year depending on the air temperature. It shoukd pick up from the Service Mpg once you drive it normally. 

When I bought my Roomster it was serviced with Shell Helix Ultra 0W 30W and I was happy with that for 4 years of motoring. The dealership has changed and my car was filled with Castrol Edge Long Life last May which I suspect is 5W 30W.  MPG does vary as I have a roundabout half a mile from my home and I use it as a measuring landmark when driving from cold. When I approach the roundabout the mpg  the display can read from 32mpg to 41mpg depending on traffic conditions and the weather.

Edited 12 December, 20187 yr by edbostan

@Lingnoi?

Has the fuel taken a dive if checked brim to brim?

 

Are they like for like new tyres or a different brand / type. 

As it is the size is slightly different from those you replaced so bigger circumference. Because new with full treads.

http://kouki.co.uk/utilities/visual-tyre-size-calculator

 

PS

Cold weather or colder weather does not have to mean poorer fuel consumption.

If you are starting and driving off and doing long enough journeys. No de-icing etc, no really low temps.

Cooler roads, less friction / traction. Good efficient running oil temp and clean cool air.

I love winter on dry roads and Winter Spec Petrol and a 1.4 TSI.

Snow, frost, salted roads are different, but then going slower might save fuel.  Stuck in the snow uses fuel though....If the engine is running keeping you alive.

Edited 12 December, 20187 yr by Offski

Well, the effective difference between 0W and 5W is that the oil pressure will build faster on a cold start with the 0W.

Other question. Are the new tyres the same nominal weight as the old ones? Not all brands are the same weight size for size, and heavier tyres mean higher fuel consumption.

Maybe, maybe not if you live where it is very flat, or you go downhill more than up!

 

Different profiles and compounds (winter / all weather / motorsport / performance) and more tread on the road surface might well have more fuel used but really does 4 kg difference of rolling wheels / tyres affect an Octavia that much.

New tyres have greater rolling resistance than worn tyres especially if steering geometry is out. Your new tyres maybe a different brand/model with radically different rolling resistance. 

 

They could have disconnected the battery or reset the ECU during a diagnostic scan so losing stored learnt parameters, will take a while to readapt.

 

Neither however should make more than a few percent, maybe 10% difference.

 

Reset all mpg averages, and start again, preferably brim to brim measurement.

On 12/12/2018 at 13:20, Lingnoi said:

First thing I did when I got home was check the tyres and as usual they were all over-inflated (I'm sure they err on the safe side by putting too much in when they're not sure).

Over inflated tyres wont cause your fuel economy to drop.

On 12/12/2018 at 17:46, xman said:

New tyres have greater rolling resistance than worn tyres especially if steering geometry is out. Your new tyres maybe a different brand/model with radically different rolling resistance. 

 

They could have disconnected the battery or reset the ECU during a diagnostic scan so losing stored learnt parameters, will take a while to readapt.

 

Neither however should make more than a few percent, maybe 10% difference.

 

Reset all mpg averages, and start again, preferably brim to brim measurement.

 

Cheers for the suggestions. I don't think the ECU was reset because the long-term MPG average was the same as previously (though obviously slowly going down now).

Filling up Saturday so I'll be able to check the actual figures rather than the computer displayed one.

 

The tyres were previously some no name one and a Pirelli. They've been replaced with Michelin Primacy 4's to match the rears.

When I had four new Michelin Primacy tyres fitted to my 1.4tsi everything felt distinctly 'different' and not in a good way.

Once the newness of the tyres had been scrubbed off over about 200 km I was much more happy about with every aspect of the tyre.

I can understand why the steering would feel overly light and exhibited low directional stability, but rolling resistance also seemed high initially and I did not expect that. My previous Dunlop SportMaxx seemed to have exceptionally low rolling resistance, so it might have been just the immediate comparison exaggerated the feeling.

Edited 14 December, 20187 yr by Gerrycan

Well I checked the brim-to-brim fuel consumption and it's gone from low 40's to mid 30's (I checked 3 fill-ups). :-(