The water temperature on my Superb goes up to almost max when I drive on a motorway but drops back down again very quickly. No problems round town just at 7 mph

What Is it a TDI, & is it a DSG, or a TSI, ?

Has it had the water pump replaced?

How many miles has it done?

It's a TDI which as far as I know has never had the water pump replaced. Mileage is 57,000

7 hours ago, TB6996 said:

It's a TDI which as far as I know has never had the water pump replaced. Mileage is 57,000

That seals it probably going to be the water pump.

Get the cambelt done at the same time.

+1 for logiclees comment.

Typically if it's the water pump, it will go towards the red line but then drop back to normal once per drive.

I.e. it will only happen once when the engine is warming up and then will be fine until the next time the engine is cold.

In the past VAG were offering 50%-60% towards the replacement cost as a goodwill payment.

I'm not sure if they're still doing this now.

I would also recommend replacing the timing belt at the same time as they have to take it off to replace the pump and it's expensive to do it alone later.