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I've just pulled the plugs on my 2.5L 86 GTV6 and I'm a little concerned by the appearance of the sparkplugs.Can anybody give me an opinion ?
The plugs are quite light grey and one of them has a fair amount of crud on the center electrode.Plugs have about 10k miles (16k km.) on them.The car has been run hard -track and highway.My Oxygen sensor reading is around 0.88v @ 3 - 4k RPM so the mixture should be about right.I'm used to looking for a nice tan -brown color but perhaps the Lodges are to be interpretated differently ? The car runs fine by the way just trying to create problems for myself

say good night gracie!

Not worth re-using...stop being cheap...just pick up another set

she'll love you for it

They look a lot like my NGK iridium plugs I pulled from my car, just in color and crud build up, at least on the side the head gasket was not leaking. Do you do a lot of short drives? It may be a case where you need to drive the car longer distances so it cleans them off, or speed a few more weekends doing the Italian tune up! (I guess you are doing this if you are tracking her).

Short trips and low RPM's are definately not involved here.This car is always highway or track driven and I love to wind her out.I've stuffed a set of NGK BP6 ??? in there for now but if something negative is going on I'd like to resolve it before it becomes serious.

How much oil consumption do you have? #6 on mine is the worst, I am guilty of the short trips, that's why I asked since mine looks like that. More white than tan/brown. Have you had head work done on the car or headers? I have both done on mine so I assumed that was contributing to the look of the plugs. Not sure I have a good answer for you, but I would be interested in what you find.

Sam I'm running stock heads and exhaust manifolds.Last winter I did a rebuild of my engine.I kept my liners and pistons but rotated the liners 90 deg.I used Total-Seal ring set.I am having oil consumption problems which I can only tie to the re-use of the pistons and liners (although they were well within spec) ,but I would have expected that if oil is being burned the plugs would look dark and grungy ?

Valve seals?

Are you running synthetic oil? I did the same as you, reused pistons and liners and total seal rings. I run Mobil 1, and it burns cleaner than normal oils, so I don't think you get the dark oily look, just burned grey left over stuff.

should be light in color but no buildup.

Murray wrote:Short trips and low RPM's are definately not involved here.This car is always highway or track driven and I love to wind her out.I've stuffed a set of NGK BP6 ??? in there for now but if something negative is going on I'd like to resolve it before it becomes serious.

I had oil consumption issues after the rebuild when using Mobil 10w40 mineral. But I switched to Castrol Syntec 5w50 and no longer have ANY oil consumption. Try the Castrol first.

Could be valve seals like Mats said.

You guys are going to make me go and get a beer I changed all my valve seals when I rebuilt as well as valves, valve guides you name it.I figure my oil consumption originates in the cylinders because I get smoke when I step on it not on decell.Compression readings are only 165 psi (at least they're about equal on all 6 cyl) which is quite a bit lower than I expected.I started the season running Castrol 20/50 Dyno (which is what I used pre-rebuild) but decided to try the 10/30 "high mileage" to see if I could cut the oil consumption.That didn't work ,so now I'm going to put in some Castrol 5/50 Syn. and see what happens.If all that fails I guess I'll have to rip the sucker apart this winter and use new pistons and liners as I probably should have done in the first place.I honed the cylinders to Total Seal specs.and drove it good and hard from minute one so I can't see how the rings could have glazed ? I'm also having doubts about my decision to use the Total Seal rings and would probably go with tried and true Deves etc.

Well Murray, I'm not sure why you used 10w30. I think it is not suitable at all. Even if it is a high mileage type oil. In my 164S the PO used 5w30 and it drank oil like crazy, 1qt/700 miles. Now I switched to Castrol 20w50 high mileage and consumption is like 1qt/3000 miles which is good for a 165K miles engine.

Murray,

You and I went down the same street with the rebuild, but my oil consumption started out very good, very little during break in, after that I went to Mobil 1 15w50 and it has steadily increased over the last 12k miles (I don't drive the car enough to get 5k between 6 months, but that will change), but the whole oil consumption thread made me want to get away from Mobil 1, I think Zamani even recommended this, so I have a couple of gallons of Amsoil on the way in 20w50, so I will try that. Did you notice the grey ash on the plugs when you were running conventional oil? My car does not smoke at all, but I believe that is do to Mobil 1 buring clean, and that is my guess at the spark plug color.

Sam I'm going to put the Castrol Syntec 5/50 in today and monitor the progress (or lack thereof) closely.
When you rebuilt did you go the same route (keeping pistons and liners with new rings)?.Have you done a compression test ?

From what I've seen in the indepenent oil analasys testing, Mobil 1 is one of the worst performing lubricants on the market. I've been an Amsoil user for 20 years now and the the importer sends these info sheets done by an outfit in the States wich constantly tests all the leading brands. They test for all things from viscosity to cleanliness, breakdown, running life, ect... Ams is allways at the top of the list in all testing. Mobil 1 is consistantly near the bottom. And the price!!! http://www.amsoil.com/performancetests/g1971/index.aspx Check it out. Its good stuff.
TIM.