We have an Octavia 1.2Tsi petrol. This weekend we had a 250 miles trip, mainly down the M6. On the way there we averaged about 46 - 50 mpg - which has been about average for the time we have had the car. On the journey we passed the 5,000 miles driven since new. We then had a 10 mile trip from Brum city centre to the NEC part motorway, part city centre driving and our fuel consumption jumped to around 60mpg. On the journey home, mainly M6 we achieved 60mpg.

 

Now, I have read comments that fuel consumption improves  as the engine is run in, but this was a sudden change. Is the engine management set up to run richer for the first 5,000 miles for some reason. The only other change since my last motorway journey is that I have had to top up the oil with the oil supplied by the dealer - Castrol Edge 5/30 but I wouldn't have thought that this would make any difference as I would have expected the dealer to have used the same oil when I picked the car up.

 

Any ideas on why this should happen so suddenly?

Did you use the same petrol station as usual?  Same time of day?  Same road conditions?  Same speed?  How much oil was topped up?  Did it have some amazing friction reducer in it?

 

Many factors affect mpg but to jump by 10 that is quite a change.

 

I don't believe for a second that the ECU would do anything different at 5000miles.   It learns and adapts to your driving style but that is normally completed within 2-3 days and 50 miles or so.

 

Best mpg 'jump' I have ever seen was on a VAG 1.8T engine where the spark plugs weren't tightened fully and the compression was reduced.  Both acceleration and mpg were noticeably better....right up until I tightened them properly.  Very easy to tell if this is the case as the radio frequency interference was awful.

I did experience something very similar on my 1.4TSi...like someone flicked a switch.

You drove southbound on the M6 and then back northbound...looking at the weather for the last few weeks, you would have had significant headwind on your southbound journey and tailwind on the way back..that could be enough to explain the fuel saving...

That's fantastic economy. I've got a yeti 1.2 tsi and I only get 35 - 42 mpg on motorways. Town driving I can get 38 mpg. I'd like the octavia 1.2 tsi if I could afford it.

Since last weekend, I am back to my usual commute and getting around 45mpg - I  will find an excuse for  another motorway trip, but at the moment it looks like a glitch - we shall see,