I have a 2006 Silverado Crew Cab LT3 with 33K. No problems with it or codes but i pulled 4 spark plugs and gap measured .037-.038". Manual says should be .040". Should I regap? Plugs are OEM AC Delco 12571164 - 41-985.

Also the 8th digit of my VIN is Z which I find to mean a 5.3L Flex Fuel engine. I didn't know my engine was Flex Fuel. Is this correct.

I'm think of replacing plugs as my MPG isn't what I would expect and I am a very lightfooted driver. Is AC Delco the way to go or another brand?

Thanks,

Mike

 

z means flex fuel capable. not that you have to run it. but yes its flex fuel capable. as far as the plugs, i'd regap and replace and look elsewhere for your mileage problem. if you do decide to replace them, some people swear by bosch, some by e3 or whatever, i personally go back with factory plugs on a stock engine.

 

Those plugs should be good for 100K miles, but if you already have some of them out then I guess it would be a good time to replace. I vote for the factory plugs. All those gimmick plugs are a waist of money IMO. Also don't worry about the flex fuel crap...I had a Suburban that was flex fuel and I ran some of the E85 garbage in it for one tank and it ran rough and the mileage offset the cheaper cost of the gas. I never ran it again.

 

The NGK's have been the best I have put in my GM motor. Much better than the delco plugs. I got a better throttle response out of them.

 

Which material is the better material when it comes to plugs? Stock from what I have heard is Iridium. Of iridium, copper, platinum, etc... which is the better material for the plugs?

 

They are puttin iridiums in now cuz they have low resistance and take less voltage to fire. Arcing is what wears metal out between two contact points. The NGK's I suggested are iridiums. As mentioned before, iridiums are made to last 100k before replacing.

 

Just getting back to the Forum after being out for a bit. RUFFNECK4LYFE which NGKs are you running?

 

Im running the IX Iridiums... http://www.autozone.com/autozone/catalog/parts/partsProduct.jsp?itemIdentifier=940882_0_0_&skuDes cription=Ngk-Ix-Iridium+/+Spark+Plug&brandName=Ngk-Ix-Iridium&displayName=Spark+Plug&categoryNValue=1429 9999&sortType=&store=1581&isSearchByPartNumber=fal se&fromWhere=&fromString=search&counter=2&itemId=3 3-0&navValue=14200033&filterByKeyWord=SPARK+PLUGS&pr oductId=940882&searchText=SPARK+PLUGS&categoryDisp layName=Routine+Maintenance&parentId=42-0
They are for more timing in the ignition when you tune.