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Thread: '97 GMC 5.7 Sierra Z71 needs OE Plugs

  1. #1
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    '97 GMC 5.7 Sierra Z71 needs OE Plugs

    I cheaped on the tune-up 40,000 miles ago not going with OE plugs and I think I'm paying the price in mileage. I used to get almost 20 mpg highway in the warmer weather (pre 10% corn in the gas, ethynol) and now its 16 mpg. Anybody got the word on the best plug for the truck with 137K miles?
    Thanks, Steve

  2. #2
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    AC Delco..........
    <----just your average 5.3

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    Senior Member 03chevy's Avatar
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    i have had bad luck when not useing oem parts... i had a 87 z24 and used wells every three months i had to replace something. then i went to the dealer and got ac delco and no problems. so if you have a gm use only ac delco parts less headaches in the long run
    A dirty mind is a terrible thing to waste!

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    Thank you, Gentlemen. I'll post my highway MPG as soon as I have returned from my next trip with OE plugs.
    Steve

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    replace the t-stat, mileage will improve

  6. #6
    z07
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    I've got dyno numbers and 1/4 mile ET's that show no correlation between expensive plugs and performance. I do, however, run NGK Iridium plugs in our Corvettes simply because they are a pain to change and those last longer than others and they don't have the problem with the pucks falling off like the platinum plugs did. With all that said, I'd use the OE spec AC Delcos without hesitation in any application where they can be changed without too much effort.

  7. #7
    Senior Member ukrkoz's Avatar
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    HALO plugs. OEM specific, only plug on the market proven by government and independent reseraches to improve power and mpg. don't expect miracles, acetone is for that, but it gives anywhere between 1.4 to 3.2% improvement. i have all cars i can on them and am very happy. no, i have no $$ interest in those.

  8. #8
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    sounds like the o2 sensor might be getting weak. Check the voltage reading with a good scan tool and see if it may be in the lower end of range.

  9. #9
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    Thanks, guys. Did pick up the OE Delco platinums. When I'm up my bud's place I'll put the scanner on for the O2.
    Priciate it,
    Steve

  10. #10
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    Ustta do dyno tune-up in Inglewood, CA. My take on spark plugs is that the better Spark plug likely has more to do with matching the heat range with your driving habits. All city= hotter heat range all open road cooler plugs. Far as gas mileage your corn alcohol has less energy per gal= less miles per gallon. Supposed to drink corn licker not put it in your gas tank...........
    Diddly

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