Don't expect to get accurate temperature readings with an IR gun. They are best for measuring relative temperatures.

The surface you aim at makes a big difference. For example, if you shoot at a shiny surface you will get a different reading than from a dull surface. I sometimes stick on pieces of masking tape just so surfaces would respond the same.

Sorry, can't help with what temperatures should be.

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5