When developing a new automotive electronic component, the component needs to be certified to withstand certain temperatures. There are several standards that list methods of testing, such as ISO 16750-4 and AEC-Q100. However, these standards list a number of 'grades' or 'temperature ranges', and it seems to be up to the reader of the standard to determine which grade applies.

In ISO 16750-3, which deals with mechanical loads, each requirement states the purpose, such as "These tests are applicable to equipment to be mounted directly on the engine" or "This test is applicable to devices under test intended for mounting on sprung masses". For temperature ranges, I can find no such guidance.

One might say that it is up to the customer to specify the required range, but how is the customer to know? Googling the problem [doesn't help](https://www.google.nl/search?q=automotive+temperature+grade), as all web pages do mention 'extended ranges' such as -40°C to +125°C, but omit how they arrived at that number.

How do I determine what the temperature range should be for a new component to be developed?