Been doing a test on our gasoline

When running regular 87 octane fuel in my 97 Jimmy 4.3L, my service engine soon light is on and the idle is rough. When I throw the mid-grade or good grade fuel in it, no light and no rough idle.

Makes me wonder just how good the actual lquality of the cheap gas we're getting since they know we're probablay buying the cheapest prices we can find for the 87 grade.

Make sense? :screwy:

in some vehicles the factory programs the ecm for premium fuel. if this is the case u my be able to program the computer(since u have full obd 2) for 87 oct, like hypertech programer. if this is not the case then buy from another location. i had this problem on my iroc camaro. would not run on anything but exxon premium.

Blazers are designed to run on 87 octane. The only benifit of higher octane fuel is it's resistence to detonation. If your engine isn't running well on 87 octane, that would indicate that you have a problem. The next time that your SES light comes on, get the codes read (AutoZone will do it for free). The codes will help you narrow down the problem. Post them here and we will help you fix it.