I have 2000 Blazer and am scheduled to go for emissions testing.
I dont have any check engine light. However I want to increase
my likelihood of passing.

What octane rating gasoline should I use? Normally I use 87
but am thinking maybe I ought to use 89 or 91 when going.

 

High octane gas might help lower NOx if your vehicle suffers from this failure. High octane burns cooler and slower (keeping NOx low), but it also produces less power which your engine might not be ready for. This could cause other emissions such as HC and CO to increase. It is recommended to use ONLY the manufactures required octane at all times, specially during a smog test. Your vehicle's emissions computer is programmed to process information based on it's required fuel octane.

 

Ok ... What about gas from BP or Shell as opposed to gas from Costco or gas from little known distributors?

 

The Top Tier designation is separate from the issue of octane levels, in order to get the designation, gasoline companies must pass tests proving defined levels of engine-cleaning effectiveness in all grades of gasoline they sell, whether it is economy (low-octane) or premium (high-octane).

 

Thanks Blazer_4x4. You sure know lots of stuff!
Glad you are a member of our forum.

 

try using shell with nitrogen in it . I've been doing this for five years now and it seems to have helped quite a bit as my 96 blazer has passed with flying colours every time, last year the boys at the test site said my engine was cleaner than a new vehicle.