I know we've had discussions about this before and there are those of us, mostly, I think of more advanced years? who were taught to use copper grease when we were learning our trade and have continued to do so but I've also become aware of the rising tide of advice that plugs should be installed "dry" because if you torque them to the recommended figures with lubricated threads you risk doing considerable damage to threads and plug body etc.
I've been researching this quite a lot lately and especially because this spring period is when I try to get to grips with the cars in the "family fleet" whilst the good weather is here. Consequently I've changed a fair number of plugs over the last few weeks.
I humbly submit that, for me, it seems to boil down to this:
1) Does the plug have a bright metal finish (ie, looks "chromed") If it does then the likelyhood is it's got a trivalent shell plating and should be installed dry IF IT'S A FIRST TIME INSTALLATION.
2) Dark metal finish, as all older plugs used to have, then some anti seize is probably a good idea. But be aware that copper based products are not perhaps the best choice because most heads are now aluminium and using a dissimilar metal is not ideal (possibility of electrolytic corrosion.) Products containing ground Aluminium or Nickel are preferred. I use Alumslip - made by the same people who make Copaslip.
That all seems straight forward enough so far doesn't it? However I still don't like the idea of leaving plugs installed literally for years as can be the case with long life modern plugs so I would like to remove the plugs every service or at least every second service just to disturb them and reduce the risk of them being "welded" in place when they finally need to be renewed. However I see a possible problem with doing this. The trivalent plating is designed to shear away from the threads so ensuring the plug doesn't get stuck in it's hole. Very good, if it works, because this should make plug removal after several years much less likely to end in tears. The problem is I've heard of instances where the plugs were still very difficult to remove after 4 or 5 years without being touched so I'm still inclined to take them out at least every second year. The trouble with doing this is that you're likely to, at least partially, shear away the trivalent plating so, by putting the same plug back in the hole dry, next time round corrosion may well have taken place.
At this moment in time I'm installing new, out of the box, bright shiny threaded plugs dry. Pretty much every plug I've bought lately has had bright shiny threads so the manufacturers seem to be all doing this plating "trick". Older "black metal" plugs I still lube with the Alumslip (although if you've got a head made of cast iron I'd be happy to use the copaslip if you want). I haven't yet removed the plugs from the Ibiza which is the only car in the fleet which has long life plugs and at 5+ years without being touched I'm sure they will leave their trivalent coating behind? So I've decided that in future they'll be coming out every two years but, whilst being fitted dry when new, they'll be getting a very light coating of Alumslip when they go back in the second time.
Of course there are problems in doing this - aren't there always - The "biggie" is that once a plug has been installed in a plug hole with lubricant on it then that hole will be contaminated with lube from then on so using a torque wrench becomes problematic. I know this is going to sound like I'm boasting but for me this isn't a problem because I've installed plugs for years simply by hand and I know how tight to do them - never had the slightest problem. Also be very sparing with the anti seize, you only need the thinnest coating and keep it away from the first couple of threads so you're not encouraging it to get into the combustion chamber.
Finally buy some dielectric grease and lightly lube the end of the HT plug cap - especially if you have the coil on plug type where each plug has it's own coil - Makes removal much easier next time.
Here's a pretty good article about it all which I found made interesting reading:https://www.driven2automotive.com/b...se-copper-grease-when-installing-spark-plugs/ The first comment at the bottom serves to support my suspicions that the trivalent plating is not the "miracle" it's claimed to be.
I've been researching this quite a lot lately and especially because this spring period is when I try to get to grips with the cars in the "family fleet" whilst the good weather is here. Consequently I've changed a fair number of plugs over the last few weeks.
I humbly submit that, for me, it seems to boil down to this:
1) Does the plug have a bright metal finish (ie, looks "chromed") If it does then the likelyhood is it's got a trivalent shell plating and should be installed dry IF IT'S A FIRST TIME INSTALLATION.
2) Dark metal finish, as all older plugs used to have, then some anti seize is probably a good idea. But be aware that copper based products are not perhaps the best choice because most heads are now aluminium and using a dissimilar metal is not ideal (possibility of electrolytic corrosion.) Products containing ground Aluminium or Nickel are preferred. I use Alumslip - made by the same people who make Copaslip.
That all seems straight forward enough so far doesn't it? However I still don't like the idea of leaving plugs installed literally for years as can be the case with long life modern plugs so I would like to remove the plugs every service or at least every second service just to disturb them and reduce the risk of them being "welded" in place when they finally need to be renewed. However I see a possible problem with doing this. The trivalent plating is designed to shear away from the threads so ensuring the plug doesn't get stuck in it's hole. Very good, if it works, because this should make plug removal after several years much less likely to end in tears. The problem is I've heard of instances where the plugs were still very difficult to remove after 4 or 5 years without being touched so I'm still inclined to take them out at least every second year. The trouble with doing this is that you're likely to, at least partially, shear away the trivalent plating so, by putting the same plug back in the hole dry, next time round corrosion may well have taken place.
At this moment in time I'm installing new, out of the box, bright shiny threaded plugs dry. Pretty much every plug I've bought lately has had bright shiny threads so the manufacturers seem to be all doing this plating "trick". Older "black metal" plugs I still lube with the Alumslip (although if you've got a head made of cast iron I'd be happy to use the copaslip if you want). I haven't yet removed the plugs from the Ibiza which is the only car in the fleet which has long life plugs and at 5+ years without being touched I'm sure they will leave their trivalent coating behind? So I've decided that in future they'll be coming out every two years but, whilst being fitted dry when new, they'll be getting a very light coating of Alumslip when they go back in the second time.
Of course there are problems in doing this - aren't there always - The "biggie" is that once a plug has been installed in a plug hole with lubricant on it then that hole will be contaminated with lube from then on so using a torque wrench becomes problematic. I know this is going to sound like I'm boasting but for me this isn't a problem because I've installed plugs for years simply by hand and I know how tight to do them - never had the slightest problem. Also be very sparing with the anti seize, you only need the thinnest coating and keep it away from the first couple of threads so you're not encouraging it to get into the combustion chamber.
Finally buy some dielectric grease and lightly lube the end of the HT plug cap - especially if you have the coil on plug type where each plug has it's own coil - Makes removal much easier next time.
Here's a pretty good article about it all which I found made interesting reading:https://www.driven2automotive.com/b...se-copper-grease-when-installing-spark-plugs/ The first comment at the bottom serves to support my suspicions that the trivalent plating is not the "miracle" it's claimed to be.