[DJHakim]

What is BMW's recommended spark plug replacement schedule for a B46 engine?

Is it reasonable for the spark plugs to be replaced at a mere 35k mi (moderate use)?

Dealer service advisor read fob of my 2019 F34 330i with 32k miles. SA reported that spark plug replacement is due at next oil change (soon).

I haven't found maintenance sched info online for B46 engine. 60k miles is mentioned in a few places for generic BMW engines. For N20/55, one source mentions "every fourth engine oil service or 60,000 miles".

The next oil change will be the 4th, but that's far from 60k miles and only 4 yrs of moderate use.

(Dealer quoted ~$800 for the replacement. Seems high.)

[Mkesler75]

Most plugs are about 60k miles. And $800 is nuts. FCP has the OEM plugs on sale for like 9 bucks right now. I just changed mine last week and it seriously took 30-45 min. You do need a specific 14mm thin walled socket 15 bucks and a proper torque wrench (rent or buy for $40 or less) but really anyone can do it.

[Mr.Smartepants]

On my service history record, the dealer noted that my spark plugs were "checked" at just over 30k miles, but I've got the F34 320i, so not sure how they "checked" the 4th plug since its buried under a support bracket mess near the firewall. I'm replacing my plugs/coils today and my car has 55k miles now.

[Billfitz]

Don't go by what BMW says, the service department is what pays the bills. That's why you were quoted the outrageous $800 price.

Per NGK: NGK Iridium IX has an iridium center electrode, however the ground electrode is a traditional nickel construction. Therefore, the ground electrode will wear out first. NGK gives them a life expectancy of 40-50k miles. But they have to temper their projections as driving conditions and motor modifications differ. Typically we have found you can expect 60,000 to 80,000 miles on an unaltered motor.

NGK Laser Iridium Spark Plugs have iridium center and a platinum ground electrodes. If installed in a regular engine, they would likely last longer than most people keep their car (barring any motor problems that can cause premature plug death). All Laser Iridium plugs are an OEM design, made for a specific engine. Some feature a special resistor or electrode design, depending on the OE requirements. In their OE application, NGK's Laser Iridium plugs typically last 80-100k miles.

[Mr.Smartepants]

Agreed! I just got done changing my plugs an hour ago and installed the new Dinan ignition coils. My plugs were absolutely fine. Plug #1 (closest to the front) had some "whiskers" growing on the ground electrode which I could have cleaned off and used for another 50k miles. The others were 100%, no wear and no discoloration.
I changed them anyway.
*Edit, I used NGK Laser Iridium IX 94201

[DJHakim]

I had it done under an extended maintenance plan. I am more certain that it was the 4th CBS-scheduled oil change that "triggered" the spark plug replacement recommendation. I think the replacement alone was ~$600.