level of octane to run?

I have a 94 Jimmy with the 4.3L Vortec(engine code w) and ran mid-grade which is octane 89 where I live. I was having problems with spark knock, rough idle(like a little miss) and surging/vibration on slow speed take-offs from like red lights or stop signs. I ran premium tonight which is was octane 93. It has took care of all my problems except the spark knock. Is it supposed to run on such high level octane only? Also is there a way to get rid of spark knock? I ask this because I had an 89 Blazer with the 4.3L TBI in the past and it ran just fine on regular grade, which is octane of 87. I also had a 96 Astro with the 4.3L Vortec motor and it ran just fine on octane of 87. Please posts your replies for I know if theres a problem causing me to have to run so high, and if not if theres something I can do to get rid of the darn spark knock. Thanks in advance.

The truck should run right on 87 octane. If everything is working right higher octane is a waste of money and results in higher emissions. The knock you speak of indicates a problem. Is the SES is on?

The truck should run right on 87 octane. If everything is working right higher octane is a waste of money and results in higher emissions. The knock you speak of indicates a problem. Is the SES is on?

No the SES light is not on. In most cases I agree that it should run right on 87 octane however, I do have my doubts on this truck because the owner manual days say that if the truck isnt run right to try running a higher octane fuel, and according to www.fueleconomy.gov it got the truck listed as running on premium fuel. I also know that the shop I had it at was unable to find the problem, but that was there guess also was it needed higher octane fuel.

No the SES light is not on. In most cases I agree that it should run right on 87 octane however, I do have my doubts on this truck because the owner manual days say that if the truck isnt run right to try running a higher octane fuel, and according to www.fueleconomy.gov it got the truck listed as running on premium fuel. I also know that the shop I had it at was unable to find the problem, but that was there guess also was it needed higher octane fuel.

Well I guess it doesnt really matter now if it should run with premium fuel or not, because it took care of the problems for about 2 hours when I was driving around last night(after getting the premium fuel) but that this morning when I started it up to leave it was just as bad as before. Yesterday morning I put some belt dressing on the belt and pullies since no one was able to find that problem either, and it did take care of the squeal about 95% all day yesterday, and its also back just as bad as before. All I can say is I have had problems with this darn truck since day one when I bought it about 2 months ago, and have well over $4,000 in it, and have had mutliple shops and individual mechanics look at it, and several shade-tree mechanics, including myself and my dad. Even after everything I have yet to have one day with out any problems. Ran great on the test drive, but from the time I got it home its been a pain in my rear. Im looking to get rid of it now and believe it I'LL BE ONE HAPPY PERSON. The 4.3L TBI motors and the 1996 and newer 4.3L Vortec motors are good but the 91-95 Vortec motors appearantly arent good for much of anything and no wonder 95% of the people I've talked to including mechanics say the motors are nothing but money-pits.