So I recently started driving my mk1 octavia 4x4 1.8T. In normal driving I get around 18mpg. I've done full service. No codes. New spark plugs and coils. Any ideas what could it be? Shouldn't I be getting at least double the mpg? 

You should be seeing at least 30MPG

People issues:

 

If you've done a full service, it might be worth checking your MAF, see when it was last changed, including fuel filter, etc.

Yessss !!!,

When I first got my Vrs in 2006, driving in "grandad mode (56mph for 25 miles) i saw 41mpg come up, was it accurate???.

Now i average 32-35mpg.

 

NB: Deans comment about the MAF is right, you can buy MAF spray cleaner I did mine couple of years ago ( still on the original one),

always get good emission readings at MOT time.

 

These engines love premium petrol I have always used Shell V power, it does help with fuel economy in the long run.

Edited 31 March, 20215 yr by Silver Bullet