Bad MPG with new plugs
- Thread starter bolantej
- Start date
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Counterpoint08
New member
I believe the v6 is supposed to use copper plugs that get changed every 30K miles, not irridiums. I'm not sure that irridiums would always cause a problem, since some people do run them in the v6, but maybe the gap is wrong or they gave you the wrong plugs? I personally would switch them out to normal copper plugs. You just can't go wrong if you follow the owner's manual.
2016 4Runner SR5
Senior Member
Always use what it came with. The "upgrade" looks great on paper but if the ignition system is not made for fancy plugs, will get poor mileage and performance. That goes for any engine in any car.
If it isn't the gaps. then other things to do is to change the gas station you are going to. Even tire pressure makes a big difference in MPG if you are under or overinflated.
If you haven't done anything else with modifications recently besides the plugs, then it might be something else. Keep in mind this is summertime, if you running the AC all the time, it might affect the MPG as well.
If you haven't done anything else with modifications recently besides the plugs, then it might be something else. Keep in mind this is summertime, if you running the AC all the time, it might affect the MPG as well.
riceandpho
Elite Member
if you want to start, check the plug gaps and also clean the maf sensor
Bluesky 07
Senior Member
Well said. Just like burning premium gas (or even midgrade) if the manual doesn't call for it and you don't live significantly above sea level. You're just wasting $.
riceandpho
Elite Member
sometime you need to check the gaps on the new plugs, its not always perfect, and got to becareful with the iridium plugs.
BlackWorksInc
New member
But premium is recommended for the V8's and the V6 for best performance/mileage.
oooh... efficient/optimal burn pattern! ...I'll see myself out.
waypoint
Member
I experienced similar disappointing initial results when I put Denso Iridium plugs in my prior Tacoma, got feedback on that forum to reset the ECM by disconnecting the battery for 30mins to clear the Long Term Fuel Trim tables. Big improvement afterward, meaning it was back to normal behavior.
The few times I had scanned while driving with the stock replacement copper plugs, the LTFT value was in the +3 to +5% range...after a few work commutes with the Iridiums it was in the +1 to 3% range. No change in fuel mileage versus copper plugs, but it stayed that way for >70K miles and was nice avoiding plug changes that long. I'd say longevity is the only value of Iridiums.
The few times I had scanned while driving with the stock replacement copper plugs, the LTFT value was in the +3 to +5% range...after a few work commutes with the Iridiums it was in the +1 to 3% range. No change in fuel mileage versus copper plugs, but it stayed that way for >70K miles and was nice avoiding plug changes that long. I'd say longevity is the only value of Iridiums.
