Hippo said:

You need to measure through/inside the filler hole so an infra red one may not be ideal due to the sensing range of view it has. A normal thermometer is what you need. Poke it through the hole and don’t force it or let go. The best way to do it is leave the car to cool over night then you know it’s cold. Then leave it on tick over and watch the temp increase when it’s time for the level check (see instructions on ere). That way you can watch what it’s doing as it increases.

I have one of these. Bit eggspensive for what it is but I got mine in the sale. Wide Range Probe Thermometer : Thermometers & Hygrometers : Maplin Electronics

The IR thermometer you linked to is ideal for the Turnip Test.

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DTO said:

So the probe is ok to stick in the filler hole as you check temp with the engine running ?
I was thinking of the probe being mashed up in the autobox

Would this food one work - Digital Probe Food Thermometer Temperature Catering New | eBay

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Nodge68 said:

As Hippo said. But don't follow the Hayes manual and take the car for a 5 mile drive. My auto is at 40°C within 10 minutes from cold leaving the engine to idle. If you take it for a drive it will be to hot.

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