I doubt your oil burning will have an affect on your test results. There are a million 90's Caravans around here with the Mitusbishi V6 that are notorious oil burners that look like a James Bond movie scene that regularly pass the same sort of test.
And, it was 1973 (for cars) when unleaded fuels started.
I can't believe you have to have a 1 ton truck tested. But since you do, go in with the fresh oil change (that morning), make sue the engine is at operating temp (drive around at least 40 minutes before the test, all in one trip, have fresh gas in the tank, and see what happens. If you fail, you'll know what you need to do (usually a tune up adjustment is all that's needed) and we can go from there.
