It is not a steady increase. It's bounces from 3 to 8 and all over in between

It's a '92 Honda Accord LX

Replace the Ignition Control Module (ICM) inside the distributor. The BLU wire from the ICM goes directly to the tachometer. Classic sign the ICM is failing. Here's how to replace it yourself:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-4.html#post265896

Check the antifreeze hondas do that when the antifreez goes down.