Time based interval on spark plugs

[Jimmy_Russells]

So, Audi has a time interval on spark plugs, in addition to mileage. This is taken from the recommended service schedule:

I know everyone is going to say they're just trying to get more money out of people, which may or may not be true. But I am wondering if there is any actual reason for this... The only thing I can think of is they are concerned about them getting stuck in the head(s) or something?

 

[Rand]

maybe they are thinking about people who dont drive alot of miles but idle and around town?

 

[atikovi]

The only thing I can think of is they are concerned about them getting stuck in the head(s) or something?

Then just break them loose and retighten, but that isn't as profitable as changing them.

 

[paulo57509]

Those NGK (?) plugs are known to wear out from non-use.

 

[TheLastWord]

Those NGK (?) plugs are known to wear out from non-use.

Really? Which NGK plugs?

Any hard evidence of this?

 

[FowVay]

It is all simply a preventive recommendation. The VW engines have the same requirements. There are known issues with misfire on these engines and keeping fresh spark plugs in them reduces or completely eliminates the likelihood of this becoming an issue. Engine misfire might also lead to increased emissions and therefore becomes something the government has their nose in. I am not certain about that but I suppose it's possible.

My friend drives a Passat and it has a recommendation of a 40,000 mile spark plug replacement interval. Because he's a DIY'er he just pulled them out and inspected the tips for erosion and reinstalled them. I think he's going to do this every 20,000 miles until the car hits 100,000 miles. This will become the hard stop and they'll get replaced regardless of their appearance.

 

[MrStamper]

I change mine every year, but i'm in the minority. Turbo 2.0L Ford ST. Purpose is to minimize carbon buildup on the threads. It takes me 15 min and i enjoy it. NGKs made in Japan are 5 bucks a pop at Rockauto. It's a no brainer. NKGs sold at american autoparts stores are made in Taiwan, at least the ones i've been to.

 

[Jimmy_Russells]

maybe they are thinking about people who dont drive alot of miles but idle and around town?

They could just base it on hours in that case. My car does have an hour meter

 

[BillyHW]

Do they corrode over time? Would there be issues with the threads seizing if you wait too long?

 

[StarCaller]

To avoid trouble, I was told by the Porsche factory to change them yearly /
Car was a 1982 911 SC /
(That car was very sensitive regarding the gap; recommended gap was 0.7mm, when I set it to 0.6mm to leave them in a little bit longer the engine started stuttering)
(And yes, it was direct advice from the company. I was living at this time like 10 miles away & just drove there & asked them)