[mithun]

All the Owner's Manuals & Service Centers are recommending to change the spark plug every 10K KMS. In reality, is it "really" necessary to change the spark plug every 10,000 KMS ?

In my sparingly used 10 year old Bajaj 4S Champion which has cloaked about 55,000 KMS, I haven't changed the OEM spark plug yet and the machine stills starts for the first kick even if it is unused for 20 days at a stretch. So what's the feasibility of changing the spark plug very 10K KMS as recommended by the manufacturer ? Is it only a way to churn out money from undiscerning customers ?

How does an old spark plug reduces the performance of a bike ?

Will it affect the mileage/pickup/smoothness of the bike ?

[pratheesh]

You should change the spark plugs in regular intervals as prescribed by the manufacturer.. because after sometime soot gets depostied in between the electrodes of the spark plug and this increases the resistance and hence sparking becomes difficult and lead to incomplete combustion of fuel.
And also the spark plugs may worn out due to improper mixture ratios or poor fuel quality. so for better sparking you need to change the spark plugs regularly as directed by the manufacturer.
As a result of new spark plug,
1) you will see an improvement in mileage due to better and improved combustion of fuel
2) Better acceleration as the combustion efficiency is improved, for the same reason the pollution levels will also go down (low HC and CO concentration in exhaust).

[adit1329]

spark plugs main job is to provide combustion. the better the combustion the better the pickup and mileage.

that is acheived by cleaner plugs and without blockage and deposits..
there is a certain life for these porcelain things,
yes 10k is the recommended change even though you feel that the plugs look good...but it is these small things that help maintain your car in good shape for a long time

[mithun]

Thanks to pratheesh and adit1329 for their valuable inputs.

[SS-Traveller]

Spark plug changes every 10k km may not be really essential. All spark plug manufacturers leave it to the vehicle manufacturer to decide how frequently to change the spark plugs. Some say 10-15k km, some say 35-40k km. At the end of the day, "reading" the plug nose is probably the best way to tell whether they need replacing - but the ability to "read" comes with experience. Even a partially worn out plug can usually be cleaned and re-gapped to full performance, and MICO used to have such a service earlier, with a sand-blasting machine that was used to clean out the plug nose, and a plug tool subsequently used to re-gap. Lately, I haven't seen a plug tool at my MASS; they chuck out my plugs at 20k km and fix new ones, because that's what the Swift manual recommends. So when I asked about it, they said plugs are not to be cleaned or gap reset! When durability is the watchword in car parts, why have spark plugs (and expensive ones at that) chucked out at 10-20k km? I remember our Amby plugs could last over 40k km, with a routine cleanup and gap reset every 10k km. Somehow, somewhere, did we take a big leap backwards in spark plug technology?

Can anyone please post more technical information on the need to replace plugs so frequently? And have we actually stopped cleaning and re-gapping plugs?

[GTO]

Spark plug changes every 10k km may not be really essential.

I agree. I don't see a need to replace plugs before 20K (at the very minimum) and, IIRC, Honda recommends a change every 30K?

[sgiitk]

I have cleaned, and regapped my plugs often in the past. The 10,000/20,000 recommendations for 2-wheelers/4-wheelers were made ages ago. That time 'points' were the way for ignition. I would suspect that 20,000 should be Ok for 4S bikes, esp. those with CDI (almost all modern bikes).

At the end of the day if you (or your mechanic) are knowledgeable the plug is your window to the innards of the engine. You can diagnose a lot of things. Also, you can judge whether you should replace the plugs or not.

[siddartha]

as long as there is no visible signs of damage and they are running fine there is no need to change them at 10k -20k intervals . your service center might recommend it so that they can make more spark plug sales.

[yatinchoubal]

I guess, that the duration for change, depends on the company and the type of plugs being used

I'm using Bosch Super 4 electrodes performance plugs

Here is some gyan I had, and the reason I bought these

Increased Acceleration: Air-fuel mixture deposits occur in driving primarily during heavy acceleration. The Super-4 spark plug from Bosch with increased ignition reliability prevents misfiring and therefore guarantees improved acceleration. In a trial, acceleration from 19 to 75 mph in third or fourth gear resulted in 0.4 s gain in each case. The acceleration distance decreased by five meters, providing driver and passengers with improved safety during overtaking. Less chance of misfiring: Bosch 'surface-air gap' technology ensures a more even wear of the electrodes. This, in turn, leads to a more reliable spark. Since the probability of a spark choosing one of the eight possible paths is equal, wear on the ground electrodes is distributed evenly over all four electrodes.

Better cold starting performance: Thanks to the improved low-temperature behaviour and self-cleaning feature, up to three times as many cold starts are possible than with conventional spark plugs. Environmental protection and protection for the catalytic converter The improved cold start behaviour and increased ignition reliability even in the warm-up phase increases fuel combustion and thus reduces HC-emissions. This also has the effect of extending the service life of the catalytic converter.

Greater Spark Power: The spark in the Super 4 loses less power than the spark in a conventional spark plug due to the four thin ground electrodes (less resistance). Spark plug efficiency therefore increases because the air/fuel mixture has up to 40% more power available for every ignition.
The Technology Behind Super 4: Super-4 differs in the following ways from conventional spark plugs:

* Four symmetrically arranged ground electrodes.
* A silver-plated centre electrode made of chrome-nickel alloy with an encased copper core.
* An electrode gap pre-set for the duration of the spark plug's life.

How does this technology work? Surface Air Gap Technology - The Plug Cleans Itself!
In the case of Super-4, the spark ignites the air/fuel mixture in much the same way as in plugs with two ground electrodes, that is, either as an air gap or as a surface air-gap. With the four ground electrodes of Super-4, this results in eight possible spark gaps. Whichever of these spark gaps is chosen, is usually quite random.
The sparks are distributed evenly around the insulator nose. If the insulator nose is contaminated at any point (e.g. with soot), the spark will skim over the contamination and jump from there to the nearest ground electrode, burning the soot away at the same time. This provides a self cleaning facility - essential for extended life and performance.
Even Electrode Wear - A More Reliable Spark > Since the probability of a spark choosing one of the eight possible paths is equal, wear on the ground electrodes is distributed evenly over all four electrodes.
>Broader Heat Range - One Plugs Fits More > The silver-plated centre electrode is an excellent heat conductor. This reduces the danger of misfiring due to overheating and extends the safe operational range of the plug into higher temperatures. Thanks to our surface air-gap technology, self-cleaning occurs even at low temperatures.
One Super 4 spark plug covers at least two of the heat ranges of conventional spark plugs. The result of this is that a large number of different vehicles (even those with conventional spark plugs) can be retrofitted with a relatively small number of Super 4 spark plugs.
Greater Spark Power - Improved Efficiency > The spark in the Super 4 loses less power than the spark in a conventional spark plug due to the four thin ground electrodes (less resistance). Spark plug efficiency therefore increases because the air/fuel mixture has up to 40% more power available for every ignition.
Improved Ignition > The likelihood of the mixture being reliably ignited decreases as the ratio of air to fuel increases (lean mixture, l > 1). In laboratory tests, reliable ignition of the fuel/air mixture was proved with the Super-4 spark plug up to l = 1.55, while with standard spark plugs in this range, more than half of all mixture ignitions were unsuccessful.

[Ravveendrra]

Originally Posted by sgiitk

I have cleaned, and regapped my plugs often in the past. The 10,000/20,000 recommendations for 2-wheelers/4-wheelers were made ages ago. That time 'points' were the way for ignition. I would suspect that 20,000 should be Ok for 4S bikes, esp. those with CDI (almost all modern bikes).

At the end of the day if you (or your mechanic) are knowledgeable the plug is your window to the innards of the engine. You can diagnose a lot of things. Also, you can judge whether you should replace the plugs or not.

Too true, plugs are the window to the inner condition of the engine and an expert can read them like your doctor reads an ecg.

The plugs do last forever sometimes. The recommendation of change every 20K or 30K or whatever is to prevent a breakdown of the vehicle midway. The resistance of the electrode in the plug does increase with use. The insulation (the porcelain outer part) becomes less effective over time. In both cases the spark becomes weaker.

If the plug is very old it might conk out any moment without any prior warning, this is why manufacturers recommend that plugs be changed at fixed intervals, (after all you dont want to stall just when the light turns green or your engine to lose power when you are halfway through overtaking a bus). Please do remember that the recommended change interval will change if you change the plugs from the stock ones.

Please do remember to clean and regap the plugs. If either of the electrodes seem worn or if you see any kind of fracture on the body - it is time to replace. The sediment on the tip of the plug should look dry and should be a light brown colour. If there is too much soot or it is dark / black, your engine needs tuning. If there is any oil, it might be time to change your piston rings etc.

If you are running a plug for longer than the recommended length, purchase a new plug and keep it in the vehicle so that it can be replaced whenever necessary.

Cheers.

[Tejas@perioimpl]

@ yatinchoubal - are you a dealer for bosch? How much do these cost?

[gowda79]

I have not changed my Spark Plug for my Suzuki Samurai for past 7yrs and running good and done nearly 80,000kms does this happen...

[Raccoon]

My Suzuki Shogun's spark plug has also not been changed for over 5 years... quite possibly seven. I don't really need to clean it even... though had to set the gap 2 - 3 times.

Spark plugs certainly don't need to be changed just because a certain distance has been covered or because they are old. Unlike oil, you can certainly tell if your plug needs changing, by visual inspection. Actually the plug's life depends so much on how you ride your vehicle, engine design, etc, etc. Auto manufacturers probably just mention "one size fits all" kind of replacement schedule which is very conservative, assuming that most people will not have their sparkies health in mind.

As for multi electrode sparkies touted by Bosch, etc., there is no scientific evidence that they make any real difference. The only advantage they are likely to have is that the plugs will likely last longer, and gap will be retained longer.

There is also a possibility that they may actually be less benificial than single electrode plugs, in that, depending on plug design, the extra electrodes actually block access to the spark, resulting in less perfect combustion.

All in all, these extra electrode thingies are one more marketing ploy. But the good thing is that they probably wont do any harm in most engines either.

[sgiitk]

Let me add a few more bits.

1. High performance plugs (whatever they call them) are not of much help in normal vehicles.

2. Modern electronic (often CDI) ignitions have a 'hot' spark, and can overcome most minor issues. Hence cleaning is not strictly required. Since I have the tools I just do it as a routine. Checking and correcting the gap is however recommended.

3. At the first sign of damage/crack to the insulator the plug must be changed. The advice to keep spare plug(s) in the vehicle, just in case, is a very sound one. Inormally keep a couple of old plugs in the tools bag, just in case.

4. Even though in principle I see nothing wrong; keeping the same (set of) plug(s) for 7 years or 50,000km does look a bit excessive to me. The last thing I want is a breakdown on the road.

[yatinchoubal]

Originally Posted by Tejas@perioimpl

@ yatinchoubal - are you a dealer for bosch? How much do these cost?

Haha.. thatz the funniest thing I have heard. No dude, I'm just using it, and found them good... and since i had done lot of R & D, before taking them, I just shared that info with you.

They cost around 280 to 300 per piece in Pune. No idea about other cities.