Oil top up improved mpg

[waynne]

I notice my mpg had dropped from 37 to around 30mpg. Tyre pressrues were ok so I checked the oil and it was at the lower end of the dipstick mark (About 1/4 of full)

I topped up the oil and my MPG has shot back up to where it was normally!

I can't think of anything else that would have helped the MPG but this gain seems rather impressive none the less!

[Eriy]

it is amazing how much a bit of oil can do

[waynne]

On closer inspection it looks like the radiator was partially blocked up with a plastic bag. It must have got sucked up there somehow

So the engine was running hotter and therefore MPG improved. I'm going to see if a piece of shaped cardboard improves things further for me!

[HDi fun]

re you sure the thermostat isn't stuck open? My mate had a 1.8T model same as yours and that used to run extremely cold.

[waynne]

That is certainly worth checking out.

[Eriy]

if you gonna take it out, mite as well replace it.

[HDi fun]

My mate's 1.8T hardly clambered out of the blue region unless you really really thrashed it's little arse off.

This wasn't a problem for her as she drove the thing with lead feet anyway but I used to find it a bit thirsty even when driven half sensibly.

That was a thermostat failure. Replacement solved the problem and got the heater working properly as well.

[waynne]

Is it the same stat that does the temperature gauge? If so this was replaced fairly recently. I was thinking of getting a hotter rated stat.

Ideally I think an engine needs to run at 92 degrees? Does that sound about right?

[HDi fun]

The stat that controls the coolant diverter is a simple old fashioned wax thermostat and is not the same component as the sender unit which feeds the coolant temp to the ECU and drives the coolant temperature gauge. It seems that these (wax 'stats) are still commonplace even in modern cars - obviously there are still some things that are hard to improve upon!

92 degrees is a common opening temperature for the stat in many cars. If they stick open then the car will run under temperature much of the time, which is not at all good for emissions or fuel efficiency.

Does the coolant warm up quickly when starting and driving off?

A stat is only about seven quid (Eurocarparts) so you might as well replace it anyway.

You will need to drain some of the coolant to do this and obviously refill and bleed air on completion.

[pgarner]

the thermostat is sperate to the coolant sender. ones a 2 min job the others a 2 hour job lol
its about £30 for parts from VW/Audi including a bottle of G12 coolant ( if your doing a full change iirc its 2 bottles for -12 or 3 bottles for -24 mixed with distilled water)

the stat should open at 87 degrees on ours

[waynne]

It does warm up quickly round town, on a steady motoway run the temp drops right down. Time to get a piece of cardboard behind the front grill.

[HDi fun]

The temperature should still be out of the blue section even under light load.
I wonder if there's any connection with this engine's propensity to sludge up if driven on short journeys exclusively.