So, 5 years and 25k miles ago, I did spark plugs. Current thinking on the forum was Coppers were ok, but platinum were probably better. Went with Bosch Platinums thinking were were going to last 50k miles.

5 years and 25k miles later I noted a misfire on idle. Not enough to trip the light, but enough to create a stumble. Also noticed rough acceleration and horrendous fuel economy ( I know, its a Disco, how bad can it be) 200 miles to a tank.

Fuel
Fuel is always premium. The only time I ever got regular was during Hurricane Sandy a few years ago when regular was the only thing you could get. And that was 1 tank. Engine oil changed out every 3500 and engine air filter every 10k.

Driving Habits.
Lots of short trips. For years, this was my defacto vehicle for driving to the bus stop to get to work( Live in NJ, Worked in NYC). Under 2 miles to the bus stop. Last few months, she has been a daily driver. 10 miles to work, 10 miles home.

Well, this time around, I went with NGK iridiums. Hope they last a little longer than 25K See Pics

 

Platinums are good, but not bosch platinums. Your experience is what I've experienced when working in an import garage 15 years ago, and helping friends out with tune-ups ever since. I'm not sure how Bosch Platinum spark plugs got such a good reputation, probably very good marketing, but they are junk.

That pic you've posted is blurry, but I'll bet if you look very closely at the plug from the misfiring cylinders, you can see where the center electrode insulating ceramic is now hollow. The very tiny wire that was the electrode has burned away. That has been my experience with Bosch Plat misfires.

EDIT: Now I will say, that vehicles that come from the factory with Bosch plugs, like some 80's BMW or Mercedes, did fine with Bosch plugs, if you use the EXACT plug called for in the manual, and not a bosch plat upgrade.

 

Bosch Platinum, Double Platinum, X2, X4 = all suck.

It's with how the plug is designed. I am extremely surprised you made it to 25K to be honest. When I was younger and new to LR's I slapped some Bosch Platinum's into my 97 Range Rover 4.6L HSE, and 3K later I started getting misfires, and a very poor running engine. Pulled the plugs and found the tips were all fouled....

Those plugs can foul very easily due to the electrode being flush with the insulator. Normal plugs like the NGK will have the electrode exposed vs flush and those plugs will not foul nearly as easy.

I run NGK Iridium spark plugs in all of my LR's now and I've had great results with them.

 

Before I started wrenching again a few years ago a mechanic put copper Champions in my truck. They lasted 13,000 miles. I put in the factory spec double-platinum Champion 7070s (RC11 PYP B4) and they're still going strong 47,000 miles later. No need for snake oil, just go with what's specified.

 

NGK is a great choice. Even Land Rover has finally seen the light, and their newer vehicles use NGK plugs from the factory.

 

Jafir, you are correct.
Tips gone, hollow center.
Went with the NGK iridiums this time around. Most Benz's use them now and all my high HP buddies (1000hp supra, 600hp rs6) swear by them, hands down.

 

This is really good info, all. Thanks for posting.

 

The Bosch 2x, 4x stuff is certainly snake oil. The NGK's just work! I haven't used a Champion plug in a very longtime, and when I tried no one had the model I needed in stock so I went with the NGK's that I've never had issues locating.

 

I second the NGKs. I've used a bunch of their different plugs in a lot of vehicles, never had a problem. I run the copper plugs in my Disco. I changed them at 25k just because that's typically the life of copper plugs and they still looked brand spanking new.

 

Please see this post of mine from five years ago and click on the Champion link explaining why double-platinum plugs are important in the "wasted spark" ignition system used in a DII.

https://landroverforums.com/forum/di...63/#post233705