Ok, I have the Regal with the 3800 V6 Series I 1992 that now has original mileage in the high 200,000s. Incidentally, they have no EGR valves.
I will soon have to go get its emissions test to renew the tags.
Here's the deal. In most states that I've lived in and in which the car has been registered, they test 4 emissions components (HC, CO, CO2 and O2). In California, they add NO (nitrogen or nitrous?).
At any rate, the car has performed fantastically on the first 4 components...extremely clean and changed minimally over the years. However, it's not as clean on the N.O., though it has always passed. I heard that this is common: cars run clean on all the others and a little dirtier, or closer to the limit, in the N.O. department.
It's been 2 years and I'm wondering how it will go. What I've heard/read is:
1 - you can tweak the timing...but these cars don't take timing adjustments, everything is sealed, and I'm not a techy
2 - run a bottle of fuel injector cleaner of a good brand (Techron) in the tank before or during its test
3 - consider bumping up from low-grade to mid-grade unleaded
Any ideas on whether this is fact or fiction? If it's true, what's the logic behind this recommendation? Any help is appreciated.