Spark plug type and gap
For years the debate has been to use ac delco or not to use ac delco........first and foremost ac delco is made and manufactured by ngk.......why buy ac delco when the same plug ngk makes is 1/3 of the price.......ac delco is almost 50.00 a set of 8 for my 99 tahoe.....ngk same plug .....19 dollars and change.......dont be fooled buy people who say only use ac delco......do some research and youll see the truth.....and some tahoes came with ngk from the factory depending where they were assembled......now chevy used to state ....gap the plug at .60.......it even says that under my hood on a sticker.....but now chevy changed it to .40,,,,,,,the .60 gap makes a tahoe idle ruff.....the idea is that the bigger the gap you can go with a smmoth idle than the better performance youll get......but less mpg.....the closest more mpg less power.......you can gap the ngk to .50 if your tahoe runs smoothly......i gap mine to .40,,,,,,,ngk plugs are pregapped to .40 and you just make sure they are.....now ..........the ngk plug you want is .....ngk tr5.....or ngk tr55........the tr55 is a hotter plug.....better mpg with tr5....i have tr5 gapped at .40,,,,,,good power and mpg......good luck and dony pay 50.00 for 8 spark plugs because they say ac delco..........OH YEAH .....DONT EVER USE BOSCH....CHAMPION....IF YOU WANT TO BE DIFFICULT YO CAN USE AUTOLIGHT IF YOUR IN A JAM, BUT NGK....NGK...NGK...NGK...NGK...