Airtight PETG container failed after a hot afternoon in my car (98C dashboard). Reprinted in ASA, it's held just fine.
This is a screw lid container I printed a while back, what I wanted from it is an airtight seal. I printed it in PETG, sealed great and lived on my desk for weeks with no problem.
I then left it in the car for one afternoon. I'm in Saudi Arabia, so out of curiosity I put an IR thermometer on the dashboard: 97.9C in direct sun!! Another spot on the dash read 88, the seat 78, and the road outside 75. PETG goes soft around 80C. so the lid sat above its softening point for hours and warped just enough to lose its seal.
Reprinted the exact same model in ASA which softens around 100C and nothing else changed. That one has been in the car for about a month now through the same afternoons and still seals. just to be clear, PETG doesn't melt, it never gets near its 230C melt temp in a car. It just goes soft, and soft is enough to ruin a seal. The lesson for me is that anything lives in or forgotten in a hot car gets printed in ASA.
EDIT: for anyone who wants the full test, all the temperature readings and photos are written up here