I used to get about 25 mpg or so but since I changed my plugs and thermostat I've been getting somewhere in the range of 16 mpg. The plugs are ngk from the dealership - think one of them is bad? Would this trip a CEL?

 

i think im having the same prolem i have Bosh Platinum 4 but idk its weird it think my gas milage got worse.

 

Make sure they were all gapped correctly. And it should trip the CEL for a misfire if one was completely bad.

And for Sy0p: You should know better than to run Bosch plugs, people have had to replace their engines because of it:
http://maxmods.dyndns.org/index.php?MaximaSparkPlugs

 

[QUOTE=drewm]Make sure they were all gapped correctly. And it should trip the CEL for a misfire if one was completely bad.
[QUOTE]

They are platinums - I didn't think you needed to gap those..

 

yeah,. my gas mileage isnt that great. ive got the bosch too, but im going to go to the ngk plugs, but either way, my gas has gone down since ive put in the bosch platinum 4s

 

NGK's are manufacturer recommendation you can run any other brand plug as long as they are for your maxima.

I have heard of all types of myths from different brands to platinum breaking off and falling inside the engine. Just not going to happen unless you go beyond the time to change or mess with heat ranges.
If your getting bad gas mileage just after changing plugs you should make sure your getting the right resistance from your wires.

 

what about denso? iriduim is supposed to be the ultimate spark plug. they make then for the maxima. there ik20. i guess since everyone is having problems with the other brands it wont hurt.

 

I am going with the densos on my next tune up. I heard somewhere that the plugs have to be laser tipped. Anybody know anything about this?

 

Maximas don't have spark plug wires. Direct ignition...

 

Yeah, check the resistance in the direct ignition wiring.

 

[QUOTE=NotoriousMAK][QUOTE=drewm]Make sure they were all gapped correctly. And it should trip the CEL for a misfire if one was completely bad.

Just imagine if some of your spark plugs were 1.1mm apart and others were .5mm apart because they were treated roughly in shipping, sound like that would be an issue? The -11 in the model number is the gap distance (1.1mm), there's a good reason they specified it in the model. Usually the gap is right, but sometimes you can get a squashed plug. I had to adjust mine before I put them in.

Also, to everyone else.... I've been on this forum for quite a few years now, and I've read the threads myself about "other brand" spark plugs..... really bad stories, the new engine stories, the bad mileage stories, the misfire stories. If you're just doing it to be cheap, then buy the coppers, they are about $1.50 each, and they will work just fine. I wrote this page this way for a reason:
http://maxmods.dyndns.org/index.php?MaximaSparkPlugs