Looking to check gearbox oil level....is using the IID tool accurate enough or would an infrared digital thermometer be better?

thank you
Richard

The iiD is probably more accurate than the infrared. John
2008 Stornoway Grey 3.6 Tdv8 Vogue - SOLD
2005 TD6 Java Black Vogue - Written off!!
GAP iiD BT-Sold

The volumetric expansion coefficient of transmission fluid is around 0.07% per °C, so if you’re 10°C out on the temperature, it’s only going to make a difference of 65cc.

By far the most significant factor in getting the fluid level correct is to have the engine running while you set the level.

Phil

Also make sure that the car is on something level.
Our drive slopes, so I had the car on blocks to compensate & initially it wasn't correct. The fluid level was out by about a litre before I corrected the blocks.  Paul,
2001 Discovery 2 TD5, 211,000 miles & climbing
2006 FFRR TDV8 Vogue 151,000 miles & now sold
Member of Midland (Land) Rover Owners Club, www.mroc.co.uk

Mr Edd (ex of Wheeler Dealers) used an infrared digital thermometer when he did the Porsche Boxster Current Fleet:-
2018 Discovery 5 3.0 HSE
2021 Ford Ranger Wildtrack
2019 Ford Mustang Bullitt 5.0 V8
1993 Defender 90 200TDI Pickup

Gone - not forgotten
2016 L405 4.4 SDV8 Vogue SE
2012 L322 4.4 Westminster
2004 L322 4.4 V8 Autobiography LE
2000 P38 RR 4.0 HSE (ex Clarkson test car)