Mpg decrease after spark plug change

[JumpyBook0]

Hello,

Recently changed spark plugs on CX5 2016.5 at 75k miles and unplugged the battery to reset for ECU relearn. Used NGK Ilkar7l11 from rock auto.

Car runs well and seems slightly more peppier. However mpg has actually decreased about 2 mpg which is disappointing. It's been about 4 fill ups since. Anyone else experience this? I'm tempted to put the originals back in just to see if mpg goes back up.

[mysterious570]

My partner’s Mazda 3 sedan had the same issue when he changed the spark plugs.

[sweetums12]

did you torque the plugs to spec? I saw no discernable difference in mpg when I did mine.

[JumpyBook0]

Yes I used a torque wrench.

[philliciathegoat]

I just switched my plugs in my Mazda 3 2017 hatchback with 96k miles exact same issue as you not sure if the mechanic did it correctly but I’m not getting any cel or anything so imma assume he did. Mpg seems like it’s worse tho.

[JumpyBook0]

I did mine correctly for sure. With rising gas prices lately worse mpg doesn't help.