An IC is not an IC. I work electronics EVERY DAY!!! I am an electrical engineer (since 1985). Ived worked at Hughes Aircraft in Radar Enngineering for 15 years and currently work a space electronics company as a reliability engineer. All I do is parts.

IC's come in so many different flavors it's ridiculous. they have different voltage requirements and have different tolerances to overvoltage. some work at 3.3v and will die at 7v. others work at 12v and will die at 30v. its all in what the technology is. (is it 1 micron, 2 micron or THE OLD STUFF).

what kind of metallization is it? what kind of circuit is it? Protection diodes? current limiting resistors??

there are so many variables.

the transistors in the electronic ignition can probably handle 60v. an ECU in a newer car is much less because as the die gets smaller, less voltage and/or current is required to get THOSE transistors to switch. They are MUCH more sensitive.

there are parts made to handle high power and those that arent. My job requires me to derate parts to mil standards and apply worst case conditions to see if they will survive in space. They are all different.

a transistor is NOT just a transistor.

Technology HAS changed. Our cars are extremely more tolerant to voltage flucuation and EMI than newer cars. They get screwed up so easily by power surges and or electrical noise.

I can run solid core spark plug wires on my car and truck because the electronics are not susceptibly to the electrical noise they produce yet it i drive close enough to a brand new caddy, I could probably blow its computer (exageration but close)

I am scheduled to run ANOTHER EMI test on electronics for the Joint Strike Fighter next month. Ive done this stuff for a long time.

those are my credentials and I am agreeing with most of what stumpy says.

you are talking NEW cars (95 and up). we are talking old cars.