changed spark plugs now the mileage dropped 2mpg

[dataguy601]

I bought a set of plugs for my '06 4x4 with 6 cyl right before the 30,000 mile mark.

Things came up and i finally got around to popping them in a couple of weeks ago. The install went easy......

I'm surprised to now see milage that dropped 2 mpg based on the scangauge. No matter how i drive it i consistantly see mileage that is about 2 mpg less than before i changed the stinking plugs.

Anybody else see this with yours??

[Pb]

Maybe one of the spark plug connectors is not plugged in good. You could be running on 5 cylinders.

What kind of plugs did you get?

[dataguy601]

Genuine Toyota plugs (denso's were in the box i think)....

Sure seems like all 6 running. Plenty of power and smooth. Just sucky mileage now.

[sears]

What were they gapped at?

[PiercedTiger]

My corolla called for platinums IIRC. It had 3 prong plugs and I replaced them with 1 or 2 prong ones (can't remember the kind) and the mileage sucked afterwards! I had them in maybe a month before I said f-it and went to buy some more. The guy at Autozone screwed up by quoting me the wrong price on Iridiums so I think I got $13/each plugs for $4/each so I took those! Engine instant ran better and mileage went back up.

I figured plugs were plugs and on a low end 4banger what difference does it make. Well, I tell you whatever the hell I bought the first time were no where near as good as the old, burned ones that had over 100k on them!

[05SCtaco]

i changed my plugs at 30k, and i'm getting about almost 17mpg with 285 tires. What are you getting per gallon?

[mhadden]

As others have mentioned, make sure you get the right plugs and double check your gaping. I thought with the copper core you could wire brush the gunk off and resuse them? If that's the case, why buy new ones?

[81shark]

if its not broke.....

put the old ones back in

[ptac4x4]

Check your milage the old fashion way by checking miles driven off a full tank. then refill. I don't have a scanguage, but maybe its reporting wrong. Or maybe your milage did drop.

[wonger]

check your engine air filter

dont gap plugs if u buy them at toyota. they are already pre gap if u buy them at toyota. unless u drop them and need to regap

[TucsonTRD]

i'm guessing the toyota plugs aren't iridium (but i don't know). but never gap iridium plugs, it is easy to scrape off the iridium with gapping tools.

[dataguy601]

I cant remember the gap but they came out of the box EXACTLY the same as the old ones that i removed.

I was averaging about 20.8 before the change and getting 18.8 now. My driving habits are the same. it even gets 2mpg less when running the cruise.

The air filter is genuine toyota only about a month old, very clean still.

I cant figure what the difference might be. The only thing different with my plugs are all are Denso. Te originals were 3 Denso, 3 NGK like everybody else. also, i added some anti-sieze to the plugs. Not much, just a little and none was on the tip....

Kinda wish that I wouldnt have messed with it. That 2 mpg was needed on my 140 mile daily commute.....

[TucsonTRD]

give the truck 3 or 4 tanks of gas to adjust. the computer just might need to relearn for optimal fuel mileage. maybe you already have, but if not, it shouldn't take too long at 140 miles a day

[toy-taco]

reply to orig post.................

the scan gauge is real time
yet it is NOT accurate

only accurate reading on gas mileage
gallons / miles !!!!!!!

the ECU [MAIN BRAIN]
is designed around specific parametres
changing those rarely bring about a gain.......

the ECU is looking directly at resistance.....voltage & timing
all plugs DONT HAVE the Same
Resistance........Nor
use the Same Voltage

as a result your mileage could change....Get Worse !!

the Prevailing Retail & MARKETING claims
to loosen your purse strings are Not a good
indicator of aftermarket parts purchases



good luck

[kingsleytim]

Not all factory plugs are half NGK and half Denso. I just replaced mine and the original factory plugs were all Denso. I replaced them with a new set from Toyota. I havent noticed any mileage loss.