How much PSI and GPM do I actually need for a gas pressure washer?

Specialist-community consensus on r/pressurewashing is that GPM (flow) matters more than PSI for getting work done, and that you need roughly 3+ GPM to reliably run a surface cleaner for driveways. For typical residential cleaning, reviewers repeatedly note that a 3,000-3,400 PSI machine at 2.3-2.6 GPM is plenty, and that 4,000+ PSI risks damaging siding and wood.