'03 Toledo 1.8 20v temperatures

Good morning, I'm just after some information regarding running temperatures for this car.
I carried out a full service on my car yesterday, changed all fluids with fully synthetic Petronas oil and Triple QX G12 coolant.

Before I carried out this service my car would get up to 90 degrees within 3/4 minutes as I live close to the motorway, which I use for my commute. It would stay put at that temp for the journey, regardless of using the heaters or not.

Since I serviced the car it builds up the temp to around 75/80 and fluctuates back and forth slightly. If using the heaters it drops and takes significantly longer to reach a constant temp.
I'm aware of how the thermostat works as well as the heater core, but I'm not sure why my car is suddenly up and down the temp gauge since replenishing the fluids.

Would it be normal for a newly serviced car with good oil and coolant to maybe run at lower temps?
I'm thinking maybe the thermostat might be on its way out and draining the system may have made it a bit worse. Hopefully I'm just being paranoid.

Any help would be appreciated, thanks.

P.s the milage is at 86,000 for this car.

spudboy6 said:

Sounds like air trapped in the system ,
Run it with heaters on max temp fan speed low . coolant cap off and pump the top and bottom rad pipes by hand to squeeze any air out , continue until car at running temp as thermostat won't open until about 86"c I think it is
Then once satisfied all air is out next step would be thermostat if temp drops when driving and raises when stationary , symptoms suggest thermostat but I expect you've got an airlock in the system

Click to expand...

Cheers fella, I'll give a go later.

If it does end up being the thermostat, is it an easy enough job to replace?

Sent from my SM-G903F using Tapatalk

Just gave my pipes a fair few squeezes. I let it get up to around 70/80 before I started and when I jumped back into the car it was showing 90.
Took it for a drive using the heaters on and off to see if it moved and it stayed put at 90.
Hopefully that'll be it, I'll find out when I drive to work in the morning.

Thank you for your help anyway, mate! Appreciate it!

Sent from my SM-G903F using Tapatalk