2.0 FSI: whistling noise and poor fuel economy

Hi All!

I'm new to this forum and here is my story.

In August last year I bought used Octavia Estate 2.0 FSI '06 reg in excellent condition.

Everything was fine until in December I noticed strange whistling sound coming from under the bonnet.

It is only there when engine is just started, i.e. "cold", after some time it goes.

I definitely wasn't there when I bought it, however I can't tell for sure when it emerged as I usually start my engine sitting inside, so can't hear it.

So, having noticed this, I went to my local skoda dealer and asked them to check what's wrong.

They suggested that it was auxiliary belt and replaced it. That looked like a truth, as sound really suggested it was a belt whistling - short whistles with even intervals.

They said if sound wouldn't vanish then they would suggest to strip it down and see what is wrong.

Sound didn't vanish. Moreover, it got much louder, I can now hear it from inside. It doesn't do any harm (as far as I'm concerned), it is just annoying.

The only thing that changed since is my fuel economy downgraded grammatically. And this is second part of my question. I used to get up to 42 mpg on motorway. Now it's barely 32 mpg. Can these two be linked somehow? If not, what might be the reason for such a change? Sorry for stupid question, my knowledge in engines is next to zero.

I hope for your help!

Edited 2 April, 201115 yr by aleguna