Plugs for Mitsubishi 6G72 12-valve

[Falcon_LS]

One of my Montero's "characteristics" is to hold onto gears longer when the spark plugs are worn down. Gas mileage also takes a serious hit, and power feels down. All goes right back to normal as soon as you replace the plugs. The recommended interval for spark plugs are 25,000 km (15,625 mi) with the factory NGK BP5ES copper plugs.

At my last interval in April '11, I decided to step up to NGK Iridium IX 2115 (BPR5EIX11) plugs, which have been on for the past 31,071 km (19,420 mi). This engine has a distributor setup, and I did this in hopes of running the plugs to 100,000 km (62,000 mi) so the distributor cap and rotor, plugs and wires are all replaced at the same interval, but it seems the plugs need to be replaced again.

I reckon the quality of the gas has quite a role to play, and I've already switched to Euro V, but I was wondering if anyone experienced with this engine had any recommendations on plugs.

Should I stick with iridum or step down to double platinums? If I stay with iridiums, are Denso 5305 plugs a good choice? What about Autolite XP64 or Champion 9007 plugs?

Also, one of my wires snapped off the bracket and touched the EGR tube, so I need new wires as well. I usually go OE with the cap/rotor and wires, but I'm considering going with Denso 6716204 or NGK 9545 wires this time round. Either of these a good choice? Thanks!

 

[Bottom_Feeder]

For a Mitsubishi (or any other Japanese car), stick with NGK or Denso plugs. You can't go wrong with either. Other brands may be fine but there is no question if you go with NGK or Denso.

If you want long service life out of a set of iridium plugs, go with NGK's 'OE Laser Iridium' line, or Denso's 'Iridium Long Life' plugs. The NGK IX line and Denso Power line are enhusiast plugs and don't last nearly as long as iridium plugs designed for OEM replacements.

Platinum plugs don't seem to have any advantages over iridiums besides price. Personally I wouldn't even consider platinum plugs if iridiums were available. The price difference isn't big enough to be prohibitive, IMO.

NGK and Denso make quality stuff. I would imagine that transfers to their plug wires. I'd say just get whichever's cheaper or comes in the color you want.

 

[GC4lunch]

Originally Posted By: Falcon_LS
The recommended interval for spark plugs are 25,000 km (15,625 mi) with the factory NGK BP5ES copper plugs.

At my last interval in April '11, I decided to step up to NGK Iridium IX 2115 (BPR5EIX11) plugs, which have been on for the past 31,071 km (19,420 mi).

Should I stick with iridum or step down to double platinums? If I stay with iridiums, are Denso 5305 plugs a good choice? What about Autolite XP64 or Champion 9007 plugs?

NGK itself says:
Originally Posted By: NGK
Q: How much of a performance improvement can I expect from changing plugs?

A: A common misconception is that changing spark plugs will result in a large power increase. In most cases, removing even seriously worn out spark plugs will only result in very modest power gains, typically about 1-2% of total engine output. This could be even less for computer-controlled vehicles, primarily because most newer vehicles have more powerful ignition systems and the vehicle's computer can make adjustments so that vehicle operation seems smoother and more seamless.

Many people think that simply supplying more spark to the firing tip can and will combust more fuel. What they don't understand is that most newer cars' engines are so efficient that they are already burning all of the available fuel. Simply adding more spark voltage can't burn more fuel because there is no more fuel to burn.

When a stock or near-stock engine is given a fresh set of spark plugs, peak efficiency is restored. The power gains that come from this restored state of tune are usually minimal. Any company that tells you that their spark plug will provide significant gains in power in a stock or near-stock engine is making blanket statements that may not be supportable.

Link for the above quotation.

If your NGK Iridium IX plugs have eroded in just 19,000 miles, it is not the center iridium electrode that has eroded, but the non-iridium ground. You would fare better with double platinums, iridium-platinums, or double iridiums. In addition to the names you have listed, you might consider Bosch single-contact Iridium spark plugs (click) -- but stay away from the Bosch multiple contact spark plug lines (Ir Fusion, Platinum+4, Platinum+2), which seem to be trouble-prone.

 

[mechtech2]

Double Plats should be great.

 

[Silk]

You don't have waste spark so double plats are a waste. The dohc is waste spark, so double plats are needed. Push the plugs too far and they'll take out the dist cap. We fit listed plugs.