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I too was thinking about this recently. I'm guessing that the longer service interval is due to the widespread use of robust and reliable fuel injection systems fitted to cars these days. Years ago I remember quite often seeing fouled or dark plugs if the carb hadn't been tuned or set up correctly for some time.
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They're not replaced until the 60k service on my Subaru. Not even inspected before then either.
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They got sooted or oiled sometimes from rich running or worse, but that did no harm and could be cleaned or burned off. But the electrodes would burn away opening the gap, so one needed to gap them once or twice in their lives. But their performance deteriorated anyway, and they were replaceable at 6 to 12,000.
I think it's the ignition of modern cars that preserves the plugs, not the fuelling. And when they do become inefficient it isn't because the gap between the electrodes is too big, but through failure of the insulation, the 'tracking' that used to set in at around 10,000 miles.
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bad news for plug manufacturers then?
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Different metals are used on many plugs these days. Platinum is common and Iridium becoming more so. These do not wear away like the older types. My Suzuki has 36000 miles scheduled for the replacement of the Iridium NGK's. They are not cheap though, the day of the "Five bob" Champions have long gone!!
Edited by boggles on 28/04/2009 at 18:51
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When I used to service my own petrol-engined cars I used to change plugs every 6k miles becuase the cost was not high and I liked the feeling of putting in something new. I always lightly greased the threads so that they were unlikely to seize, a possible problem when plugs are left in for 4-5 years and 60k miles!
My current cars are diesels and I can't even find the spark plugs:-)
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We changed my dads on his Fiesta mainly to stop them from rusting into the block, the plugs were 20k old but the the car ran so much better afterwards, we never realised there was a problem with the plugs.
Diesels don't have spark plugs they have glow plugs.
A lot of petrol engines like mine now have a coil pack which sits on top of the plugs which means you don't need HT leads, this system is cheaper and should be more reliable.
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Do - or did - some motorcycles eat plugs?
Perhaps one of the backroom's resident bikers would care to comment.
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In 1996, the US Ford Taurus's 3.0 V6 had spark plug changes at 160,000k intervals amongst other low maintenance features.
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Provided the plug gap is correctly maintained and the electrodes are still in reasonable condition, I would of thought that new plugs are largely unnecessary.
Its important to check the gap, especially with cars fitted with modern coil packs. As the plugs wear, the gap increases and the striking voltage increases - this stresses a lot of coil packs and can lead to failure.
Skoda approach is to change at 40,000 miles with no inspection in between. The ones I took out of my Skoda at 40,000 miles were still in very good condition but the gap had increased by about 25%.
On the other hand a set of plugs is only about £10, whereas those coilpacks are £25 each.
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I usually stick GM quad electrode plugs in my bangernomics Vauxhalls if I do change the plugs, these are pretty much impossible to adjust anyway, about 3 quid a plug from memory.
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>>Diesels don't have spark plugs they have glow plugs.
I know, Rattle! That's what the :-) was meant to indicate. Maybe we need emoticons here?
Incidentally, do glow plugs need replacing? And if so, how often? My Audi has done 101k miles and it still has the originals.
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Incidentally, do glow plugs need replacing?
Only when they stop working. You will know when it happens.
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No need for regualr replacement of glow plugs but they should be checked at first sign of starting problems.
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Alfa twinspark engines are due new plugs only every 60,000 miles. I've done three changes so far. Each time the plugs came out easily and still looked in good condition. Although at 8 plugs per change, it is just as well that new ones are needed only every 60k.
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Do - or did - some motorcycles eat plugs?
Two-stoke ones certainly ate them up. I well recall in my youth popping round to the local Esso garage to get the plugs cleaned on their "plug cleaning sand blaster". ISTR most garges had them in those days.
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what martint123 you never cleaned them and put them in the oven on a cold morning start
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I can remember having Lodge plugs that you could strip down... great on your mothers kitchen table on a Saturday morning. That whiff of petrol and a bit of carbon to play with..
Ner ner na ner ner... ;-) Don`t know the fun you missed - Rattle;-)
Edited by oilrag on 28/04/2009 at 22:40
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I vaguely remember my Toyota MR2 needed the plugs replacing every 80,000 miles.
I also remember the old taking out the spark plugs and heating them in the oven routine. Cars in the 70s really were crap.
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I also remember the old taking out the spark plugs and heating them in the oven routine.
Gosh yes, I'd quite forgotten that one. I can remember my father doing that on winters mornings.
He had "treated" himself to a VDP 1300 auto as his retirement gift to himself. Having had many cars but latterly 240 series Volvos he must have decided to downsize.
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>>I also remember the old taking out the spark plugs and heating them in the oven routine. Cars in the 70s really were crap.>>
My father used to do this quite regularly in the 1950s on a 1947 Austin 8...:-)
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Yes mostly the 2 cycle engines. I remember a cartoon years ago showing a Bultaco rider wearing a bandoleer,,, full of replacement plugs.
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Perhaps one of the backroom's resident bikers would care to comment..>> Do - or did - some motorcycles eat plugs?
My soon to be 25 year old RD500 two stroke doesn't eat plugs. I can't say the engine is the best in the world but I do know that it is set up properly. I think most of the old 2 stroke plugs oiled/sooted/ate themselves due to incorrect fettling by their owners. The current plugs have been in for about 3 years (a measly 1500 miles).
As for cars, I can't remember the last time that I noticed any difference when new plugs were fitted
Edited by V4 Heaven on 28/04/2009 at 23:33
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My ZZR is on the same plugs I bought it with 5 yrs ago. It's done 14,000 miles in that time. NGK CR9E's removed, cleaned and regapped annually and they're still fine.
Cheers
DP
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They don't seem to need changing with anything like the frequency they used to. It seems to be around 40k/4 years for modern engines.
On my first car, an 82Y 1.6 Capri, I remember changing the plugs quite regularly. I always bought Champion 'Double Copper'. Also remember having to change plug leads and daily sprays of 'Damp Start' in wet weather...
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Also remember having to change plug leads and daily sprays of 'Damp Start' in wet weather...
>
I have heard about this process :-)
Over several decades I have never sprayed anything like that on plug leads or the coil lead of my cars ( Fords) .
I have however always kept the leads as clean as possible, often using meths to do this.
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My Mondeo V6 broke down shortly after I bought it, my mate tried all sorts, new HT leads, coil pack, fuel pump etc. She would turn over and over but just wouldn't catch at all, we thought we had it sorted with the pump but sure enough it stopped again shortly afterwards.
The spark plugs were changed and that was the end of the problems, it seems that despite what the service book said they were the original plugs that had never been changed (just over 7 years old when I got it)
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Are new spark plugs necessary >>
Below link shows that 100,000 miles is now common for modern tech spark plugs:
www.google.co.uk/search?hl=en&q=spark+plugs+change...=
Edited by jbif on 29/04/2009 at 00:59
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Below link shows that 100 000 miles is now common for modern tech spark plugs:
SQ
Yep - this goes along with what the local Honda garage said about my CRV - replace plugs at 100,000 miles.
Edited by Dynamic Dave on 29/04/2009 at 11:14
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For my MGtf, the dealer's service manager reckoned 60,000 miles.
Slightly off the point, I got damp weather starting problems with my three 2CVs. The problems are usually due to shorting of the leads on the cross brace between the wings, a bit of sloppy design. Wrapping the leads with spirals of stiff wiring cable to hold them off the brace brings an improvement.
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Do - or did - some motorcycles eat plugs?
Some did, I think that's one reason for so many bikes using CDI (capacitive discharge ignition) systems so they'd have half a chance of working for longer.
Early Porsche 911s had it, as did Tatra 603s, in a sinister looking black aluminium box that whistled when you turn the ignition key....
I'm doing my bit for plug manufacturers, replacing 8 at a time ;-)
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From the point of view of someone who just waited till something went wrong with starting, fuel consumption etc.: It never did. I bought only 2 sets of plugs for the 150000 mile 15 year Astra 1.6i 16V: thew away originals at 10,000 and put in some posh ones (iridium, for no other reason than they cost more and were reputable ?NGK). Thought I'd better get some more around 70,000, but it was no worse and no better, so I put the first iridium set back in around 140,000 despite there being no problem. The car died, but starting and fuel consumption remained good to the end.
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I reckon unleaded fuel has a lot to do with longer spark plug life, they don't seem to foul up like they used to running on leaded. Could be wrong though. NC?
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More accurate fuelling plays a part too, I suspect.
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Fuel and fuelling have nothing whatsoever to do with it. As I said above, it's the ignition system that makes the difference. Back in the contact-breaker days, aftermarket or piggyback electronic systems made the plugs last much longer.
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im with the captain
engines are much cleaner since they went leaded
i do agree with better metering of the stuff too and feel a new thread coming on------
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>>Could be wrong though. NC?
Sorry, I don't know.
I tend to think that you're right, there's much less fouling than there used to be, and much better control over mixture.
I also suspect that manufacturers have been driving plug suppliers to improve their materials and quality to help increase service intervals.
The much higher power available from modern ignition systems would probably lead to more rapid errosion and blunting of electrode corners if you fitted an old technology/material plug.
All pure speculation though...
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Golden Lodge plugs were so attractive and `feel good` in the hand, you would keep a new set permanently on a bookshelf in the lounge - if there weren`t women around to kick up a fuss ;-(
Even though you`ve only owned diesels since 92..
Edited by oilrag on 29/04/2009 at 22:22
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Ive never tried spitfire plugs either, dont go in for all that stuff.
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