Pulling the Bosch+4s and installing NGKs to correct a rough idle and/or poor MPG could be nothing more then a corrective action that does not correct the root cause of the problem.

The NGKs have a much smaller spark gap vs the Bosch 4s (it takes less energy to jump the gap of the NGKs. The root cause could be issues with the ignition components and/or low voltage).

Pros of Bosch +4s......

1) Longer spark gap (better ignition of fuel/air charge).

2) Center electrode unobstructed (flame kernel path travels towards piston center, causing combustion chamber ignition event to occur in a "center/out" pattern. NGKs "shroud" the flame kernel with a "J" electrode, causing the initial flame kernel event to travel toward cylinder wall. Engine dyno tuners have seen 2% hp/tq increases just by plug indexing, turning the plug so the "J" electrode is not between the center electrode and piston center).

3) 4 possible spark paths (slow motion in cylinder camera analysis has show less the 1% "no ignition" events with 4 path plugs, around 3% with single path plugs.

Nothing but good news if your ignition system can jump the longer gaps.

Changed out a front turn signal lamp socket & bulb. Only dropped one headlamp housing screw into the great void behind the bumper cover before determining it's easier to reinstall if the fog lamp housing is out too!

2002 X5 3.0 276,300 miles
2004 325i 119,700 miles

Replaced my left front axle with an FEQ Saturday morning.

Had the pleasure of that one wiping out my rack 30 miles later and just got my car back yesterday from installing a new GKN, New steering Rack, New engine mounts, all new power steering pressure hoses, new PS res, thermostat, and temp sensor on the waterpump

It was a fun week for sure.

Last post for pictures:
http://www.xoutpost.com/bmw-sav-foru...eak-coils.html

Just giving you my experience with that particular plug. I've run them in other cars as well with no problems. I hope he (and you) continue to experience no ill affects to running those.

After seeing the number of necessary replacements from the +4's I won't recommend or install them for anything European or even new (within the last 3 years or so). Never seen any problems with NGK Iridiums unless they were just worn out or the car was leaking oil onto them through the valve cover.

Just curious how much for the spark plugs? I just bought 8 for my 540i and was charged 13.XX per at the dealer.

They sold you +4's at the dealer?

Bav Auto has +4's for $6/ea.

OEM's for $22/ea

NGK's for $10/ea

Edit: Here's a link for you. http://www.bavauto.com/shop.asp?HC1=...=2001&HCM=540i

I recently did the coils, wires and distro in my 95 302 Bronco and while I was at it, I inspected the +4.... 100K+ miles later, it looks great. How does she run? like clockwork. she cranks and turns over faster than the 4.6. Seriously, just a tap forward to start and back, the Bronco fires up and runs solid. It was suppose to go to my 540 before I messed it up so I had a set of extra +4's.

I didn't say they were bad in ALL vehicles... and said older domestic stuff loves them as well as older imports.

I'm glad you guys have great experiences with your +4's. Again, I am just giving you the experience I saw at a euro specialty shop where we saw hundreds (if not thousands) of cars a year. I've run +4's in our old Honda Civic and our Mustang. And they lasted 60k+ miles in those just fine. Everything else got/gets NGK's.

Amazon sell the Bosch for about 5.00 each and the NGK are about 7.00 each.

Sorry I didn't realize +4s were not the oem. I got the oem plugs