Spark Plugs

[joderest]

I know this is going to open a can of worms.

BUT

Decades ago, you only replaced a spark plug if it had gone faulty, part of your normal service was to remove, clean and re gap spark plugs. Now it seems every one replaces them at the drop of a hat.
So, my question to you, would you clean and re gap, and if all good, just put them back in
or
Buy new ones, check the gap and put those in, throwing perfectly functioning items away

I await the onslaught

 

[EmilysDad]

think they're often thrown away so that dealers can maintain their eleventeen thousand mile service schedules

 

[AMGeed]

think they're often thrown away so that dealers can maintain their eleventeen thousand mile service schedules

Changing plugs every 3 or 4 years or 31k/50k miles seems sensible to me. The tips will burn away over time and I certainly noticed the car felt smoother after a plug change in my E55.

As far as cleaning and re-gapping one plug if its misfiring, certainly unless they had been in the car for a long time and were due to be changed sooner than later. Then I'd just change them all.
There was a time, long ago, when I changed the plugs every yearly service in other brand cars. Spark plug research and manufacture has probably moved things on from those days, hence the much longer intervals between changes.

 

[Blobcat]

I’m presuming it’s not your ML270 you’re talking about changing the spark plugs on…

I get them changed at the interval and don’t look at them in between.

On my bike I change every 2 years or it misfires at high revs (>12k)

 

[pgh13]

I know this is going to open a can of worms.

BUT

Decades ago, you only replaced a spark plug if it had gone faulty, part of your normal service was to remove, clean and re gap spark plugs. Now it seems every one replaces them at the drop of a hat.
So, my question to you, would you clean and re gap, and if all good, just put them back in
or
Buy new ones, check the gap and put those in, throwing perfectly functioning items away

I await the onslaught

Back in the day, plugs were a regularly replaced item along with points, but they were dirt cheap; 4 plugs for a quid (admittedly, Champion) and another 5 bob for points, so hardly worth questioning the need to change them.

 

[rayhennig]

My MB plugs are less than 5€ each so I change every 20ish k Kms for a grand total of less than 30€.

R

 

[Mr Greedy]

I understand part of the reason for some plug change intervals is to ensure they can be removed every 4 years and so that you get fresh metal in the head. If they were left for 40k miles and 12 years (Just as an example), it could be wrecked head time.

 

[AnthonyUK]

I changed them recently on an 85k M112 and cannot see when they were last changed but it would have been some years ago.
They honestly didn't need to be replaced and have not made any difference that I can tell.
The issue for me was that I wanted to see what condition they were in and if you are going to that effort to check 12 plugs then you may as well replace them.

 

[joderest]

all good comments, i ask because i am about to service my daughters Mini, as she is a student, Dad has to pay for parts !!!
NGK ( my choice of plug for any car) work out at over £50 for four.
I understand that plugs left in the engine for years could result in an issue taking them out, and i do intend to remove her plugs, clean and put back in (unless i see a problem, like a dodgy electrode) .
Its just i hate waste, and throwing away an item that is perfectly serviceable just seems such a waste.

Oh well, you can call me tight, and no, i have never tried to install spark plugs in the ML270 !!!!! (anyway, cant find the holes they are supposed to go into !)

 

[EmilysDad]

all good comments, i ask because i am about to service my daughters Mini, as she is a student, Dad has to pay for parts !!!
.....

Are they single electrode? Many plugs these days are multi electrode (2, 3 or 4) .... for longer life ... and you don't gap them

 

[AndySlade]

all good comments, i ask because i am about to service my daughters Mini, as she is a student, Dad has to pay for parts !!!
NGK ( my choice of plug for any car) work out at over £50 for four.
I understand that plugs left in the engine for years could result in an issue taking them out, and i do intend to remove her plugs, clean and put back in (unless i see a problem, like a dodgy electrode) .
Its just i hate waste, and throwing away an item that is perfectly serviceable just seems such a waste.

Oh well, you can call me tight, and no, i have never tried to install spark plugs in the ML270 !!!!! (anyway, cant find the holes they are supposed to go into !)

I think I'd change them for your own piece of mind, knowing they have been changed when easy and convenient to do so. I'd then clean and gap old ones (if possible) and keep in garage as spares. In my case probably never to be found if and when needed.

 

[sonic]

I’m presuming it’s not your ML270 you’re talking about changing the spark plugs on…

I get them changed at the interval and don’t look at them in between.

On my bike I change every 2 years or it misfires at high revs (>12k)

Must be a BMW!

 

[sonic]

I am sure the plug change on our old SLK200K was 60K miles.
I cant remember the last time I cleaned a plug or had a misfire, its well over 20 years ago.
I did 67K miles on my VFR800 only changed the plugs once at 30K miles.

 

[Blobcat]

Must be a BMW!

My BM won’t rev to 12k!
It’s my ‘93 CBR600, fine to 12K then misfires to 13.5k if the plugs are >2 years old

 

[AndySlade]

My Yamaha two stroke used to eat spark plugs! Would run fine and then be a pig to start and then run rough, changing spark plugs always fixed it. Was even known to buy the expensive Platinum plugs, they lasted longer but also went duff eventually. Who rembers Bel-Ray oil for two strokes?

 

[mioba]

Change all the way - as specified. Tut tut tut cutting corners.
Plugs wear out and loose there oomph, a clean and a regap wont help there.

 

[AnthonyUK]

Plugs wear out and loose there oomph, a clean and a regap wont help there.

They are a simple conductor so a pretty binary mode of operation. The whole point of re-gapping is to account for the wear
Still it is easier to change a plug than the head and for the time they last, it isn't a great expense to replace them.

 

[malcolm E53 AMG]

Providing you buy the manufacturers OEM plugs they should be good for 40k miles but most recommend changing them at 20k miles - they are made from much better materials nowadays compared to what was available 30 years ago. Incidentally BMW recommend changing them every two years but for me that would be a complete waste as they would only cover <5000 miles so will push it out to every 4 years

 

[LostKiwi]

Smarts eat spark plugs.
The change interval is every second service so around 12k miles. Three cylinders, six plugs. The lower plugs are almost always forgotten about, especially number 3 as it's a swine to get to (turbo in the way).
When I did mine first time the outer electrode was almost worn completely away from spark erosion.