Sounds like even 100k is to much, 80k might be a better number.

i agree, 100k is recommended but better safe than sorry, plus our babies need love and affection lol

I've not quite hit 50K on EITHER my wife's 04 325Ci or my 06 3.0 X5..

I wasn't planning on EVER replacing the plugs since at the rate we're going it'll be another 5-6 years before we are even close to 100K (the recommended change point).

Is there any value in changing them early ? mileage, power, etc or is it only noticeable on the 4.0+ engines..?

ed

See first post ;) Any engine, from your lawn mower to your car can benefit from new plugs when they get tired and old. Problem is they don't just get old overnight, they gradually get weaker and you won't notice the change till you just do them. At only $36 and some change to do your car, it couldn't hurt if you felt the need or were just bored one weekend.

I wanted to say a bunch but it is simple. The core of the plug can develop fractures and increased resistance. Tell me how YOU test resistance @ 25k plus volts. Not on a plug.... not that easy.
All the new electrode materials will last quite some time. Gone are the days of copper tips. Tips aren't the problem unless they are clearly eroded. Which they shouldn't be in a normal application tuned correctly......ever.
Detonation and heat destroys electrodes. Way more than your stock engine is gonna see normally.

Dont trust the stealers, change as many fluids as you can, as often as you can, it certainly is not going to hurt. 15k oil changes are crazy, unless your paying for them, lol. Fresh fluids are your friend;)

Plugs are a mileage thing. Seeing as BMW says OE plugs are good for 100,000 miles, you are only half way there. Yours should be fine for another 40,000 or 50,000 miles, but if you want to go James's route and change them now, you will still have to change them at 100,000 miles if you use the cheaper after market plugs. Unless changing plugs gets you off, you still have a lot of miles left on yours.

There is plenty of evidence that BMW's running 15,000 mile oil intervals is just fine, first trans fluid changes at higher mileage can contribute to failures and leaving OE plugs in for 100,000 works. Have you ever heard of anyone who's BMW engine failed do to wear becaue of following 15,000 mile oil intervals?

See, while intellectually I agree that it makes sense to replace "stuff" that wears or gets less effective over time, I want to think that the engineers at BMW didn't pull a number out of the air when it came to determining replacement intervals. Now if you live in a really dusty climate or 80% of your driving is bumper to bumper, or some other extreme environment, then those fellows in Bavaria may not have it down exactly.

But for those of us (and you can tell just by our mileage) that don't put a lot of "stress" on the engine and power train, I believe that the recommended service points are there for a reason, and mere mortals (like me) don't have any business re-designing their scientifically developed program.

No, I don't believe in Santa Claus or the Tooth Fairy...

I do believe in buying GOOD, PREMIUM gas though.. :D

ed

I agree. I change the oil, filters, brake fluid, coolant, etc when BMW recommends. However, I have not touched the trans fluid and am on the original plugs at 120,000 miles. I am going to do the plugs in the next few weeks, but our X still runs like a top. I only use 93 gas as well. I have to be honest, most people are not going to tell a difference in power between plugs changed at 30,000, 50,000 or 100,000 miles. The ones who say they did probably felt a difference because they knew they were changed, imo. I would guarantee that if I snuck into their garage and changed out their OE plugs with 50,000 miles, they would not notice. Unless there were other issues of course.

I didn't say tranny.
Agree to disagree. If you like, just do whatever BMW tells you to, its your perogitive.