New Copper Spark Plugs

I received a set of four NGK V-Power BKR7E-4644 earlier this week as a birthday present from one of our Gearheads. Today's my birthday and I took the day off. It was warm enough to install them. They came gapped between 0.030 and 0.034" and I regapped them to 0.034-0.035". My coin gapper has gap loops at 0.030", 0.034", and 0.035" and I adjusted the ground strap so that I could slide the 0.034" loop through but not the 0.035" loop resulting in all four plugs being gapped to within 0.0004" of each other. Remember, the original spec in GM's Global Connect for dealerships for the Cruze 1.4T engine was 0.033"-0.037".

I had left my car where the front of the car would be in the sun this morning, which helped some, but it was still cold enough that I had to run the engine to warm up the EcoTec cover so I wouldn't break any plastic clips when pulling it off.

Pulled the cover off, then unscrewed and pulled out the ignition rail and boots. I unscrewed each of the four plugs and then took the rachet handle off and hand unscrewed the rest of the way. I put the new plugs in and hand tightened without my rachet. Then I used my rachet, which is set to 18 ft-lbs and tightened to slightly before the torque setting triggered - my plugs are sitting at 16-17 ft-lbs of torque each. Then I took a clean damp rag and wiped down the top of the engine block, the ignition rail valley and the ignition rail itself, paying close attention to the boots themselves. There was a lot of dust and dirt from winter driving on everything. I checked and released all four springs from where they were jammed in the sides of the boots and reassembled the rail. Before putting the cover back on I started the engine to ensure a smooth idle. Idle was smooth so I put the cover on and went for a drive.

Initial impressions - very smooth idle. Once the engine had a little warm up time I took it up to 6200 RPM in second and then when it was at operating temperature I took it to 6200 RPM again followed by 5700 in 3rd. I held the engine at 5000 RPM in third for half a mile. Based on throttle feedback there was no knocking or spark blowout basically from idle to the red line.

Since I was below a quarter tank gas and needed to go to Home Depot anyway I had planned on filling with Shell V-Power 91 octane at an extremely busy Shell station just down the street from Home Depot. However, with the car driving like a car should - no hesitation, throttle pulsing, etc., I put in 87 octane which is about 13 cents less per gallon. Remember, the standard octanes in Denver are 85, 87, 91. Last winter I tried dropping from 91 to 87 octane and went back to 91 because as soon as the temperatures rose above 65 the ECU would switch to the low octane maps and the car would run like a slug. I'm going to give 87 a good test to see if I can now run 87 at least in cold weather and I'll even give it a try as the weather warms. If I can run 87 for at least three months of the year the fuel savings will pay for a set of Copper plugs each spring.

[HR][/HR]
Now for the old OEM NGK IFR7X-7G plugs - I gapped them to 0.035 around 35,000 miles ago. Over the past month or so I noticed a small amount of high RPM spark blowout and a very slight uneven idle before the engine warmed up. I had attributed the idle to the cold weather because cars simply don't idle as well in very cold weather. However, upon measurement I discovered three were at 0.037-0.038 and one was at 0.040".

I also find it interesting that NGK listed those plugs as 0.028" gap yet when I pulled them out at 6,000 miles two were at 0.023" and two at 0.025". Those plugs weren't gapped correctly based on what GM ordered and NGK's own on-line spark plug part decoder. This is a supplier error that given the statement in the 2014 US Cruze owners manual about the 0.025"-0,028" applying only to replacement spark plugs (bottom of page 12-3, second printing, 2014 Cruze Owners Manual).

I was going to take and post a picture of my old plugs but when I looked at them they are only marginally darker than the ones I put in and there is no indication of excessive heat on the plugs.

[hr][/hr]
Comments on GM's original spark plug gap spec found in GM Global Connect vs. http://www.cruzetalk.com/forum/10-p...cial-statement-regarding-spark-plug-gaps.html to XtremeRevolution.

I gapped my OEM plugs to 0.035" around 6,000 miles on my odometer and when I measured them after removal today three had gaps of 0.037"-0.038" and one at 0.040". Assuming I screwed up the regap on the one plug this still leaves 0.002" electrode erosion over 35,000 miles. Extrapolating this to 60,000 miles this means you don't want to start your OEM spark plugs more than 0.032" and for 100,000 miles more than 0.029". Giving a small amount of engineering wiggle room and the standard coin gapper's loops this means that for the 2011 to 2013 US Cruzen with their 97,000 mile spark plug replacement schedule (owners manual) you don't want to start larger than 0.028". For the 2014 with the 60,000 mile spark plug replacement you don't want to start larger than 0.030". The standard OEM brand coin gapper has gap loops at 0.028", 0.030", 0.034", and 0.035". This erosion rate, combined with the spark blowout I was starting to experience is our first evidence that GM's official response has some honest engineering thought behind it vs. just marketing and legalese to save money by not having to print and send out a page change to all the 2011 & 2012 owner manuals. I wish this had been communicated in their response as it is critical information for the DIY crowd. Instead the mealy mouths in their marketing and legal departments dumbed down the response and frankly, made GM look bad.

I strongly recommend that anyone who has gapped their OEM plugs to 0.035 or higher to check them at least annually or every 15,000-20,000 miles, whichever comes first.