Here in N.J., there are a couple of special categories for cars 25+ year old cars.

One is a category for "show cars" that are given QQ prefix "historic" license plates -- but these cars (or rather, their license plates) are only street legal on weekends (presumeably to go to and from car shows) -- if you need to go to a shop for repairs during the week, you have to trailer it. No inspection at all (no windshield sticker) with those plates.

The second is a category for "little-used" cars -- they need an inspection every two years just to certify their accumulated mileage which must be less than 3,000 miles a year (6,000 miles between inspections), and to show that they're covered by a special "collectible" insurance policy (that many insurance companies cannot issue). Such cars get a distinctive triangular windshield sticker in lieu of the regular square ones.

Other than that, older cars such as my own '84 need a regular emissions inspection every two years like any other car.

Because Washington has recently (in 2008) adopted the same emissions criteria (for zip codes close around Seattle) as California and the northeast states (including my own NJ), I'm wondering if the 25+ rule applies as it does here in NJ, or alternatively that you're "scott free" on that. I've been through the WA DOT website and didn't see the 25+ exclusion waiving all cars that you wrote about.

Are you sure?