So my Sub just rolled over 100,000 and I changed the plugs last weekend.

I opted for Autolite Double Platinum plugs, and got some Duralast wires from Autozone. I wasn't a fan of the fact that the new wire sets are 2-3 inches longer than the stock ones but went ahead anyway.

The plugs came with a gap but it was not the same dimension as the .04 gap recommended by the "Wal Mart" digital plug selector thing.

I gapped them to .04 and stuck them in. Truck currently has no misfires or missing, and power is good...but my wife seems to think the mileage is not what it should be. We used to average 15.4 miles per gallon in town and now the average is down.

I drove it on the highway and it seemed to get better mileage: like cruising at 68-70 mph with cruise set, I was regularly bumping 21-22 miles per gallon when I kept resetting the mileage setting on the digital display.

My question is...what's the gap really supposed to be? I think these plugs come with a .063 gap...should I have left them alone?

thanks!

Chriss

 

if it ain't broke don't fix it, if nothing is acting up or going wrong I would just leave them alone for now

 

Welcome to the forum.

Maybe someone else can chime in but the best info I could find stated that the original AC platinum plugs were gapped @ .060" and when GM changed to AC iridium, the gap went to .040". Best bet is to ask your dealer service although since you elected to put a Ford plug in, info may not be germane. That also may be why your mpg went down.

BTW why did you elect to get those plugs? Anyway you should always check plug gap before install as they don't come pre-gapped reliably from the factory.

What mpg data is your wife basing her concern upon?

 

what do you mean a FORD plug? Autolite says it replaces AC Delco 41-805 and 41-983. Wasnt one of those original on the 2006 'burb 5.3 flex fuel? Sorry if I'm not the total Chevy purist... I went with the plugs because they seemed a good choice...and according to the autolite book were a recommended plug for my vehicle.

nothing else seems to be wrong...it is only 5 degrees out so i'm sure that is impacting mileage. I'm going to leave it alone for now. I'll keep you posted.

wife is basing her findings on the digital mileage readout in the dash.

Thanks for the help so far.

 

There is no substitute for the large SUV-Tahoe and Suburban,
and there is no substitute for a great extended warranty-GMPP
David Matthews(ACWII)

 

Welcome to the forum,

The AC Delco plug is your best bet, its manufacture supported and will give you the best MPG.
If there was a better plug out there GM would have used it...
I like to point out that the plug in your truck is the same one they use in the Corvette

 

I was just referring to the fact that Autolite used to be the Ford OEM plug, maybe it isn't anymore.

But like in2pro said, AC Delco is really the one meant for the Chevy. I don't know what it is about spark plugs anymore but engines w/ computer controls seem to be very sensitive to have the right one.

Had a '89 Dodge minivan w/ a Mits 3.0L V6 w/ OEM Champions. Replaced them w/ Bosch platinum tips and it burned them up in 500 mi. The Dodge tech said should stick w/ the Champions. But if the Autolites work for you, that's great.

 

Yeah, thanks all! I'm not sure the Autolites are going to cut it long term...going on a road trip in 2 days for a week...should be good for a couple thousand miles...we'll see how they do and i'll provide feedback.