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Oil On Spark Plugs

By bobbiw, February 4, 2013



The last time i changed the oil, i noticed oil on the tip of the spark plugs, i had new plug gaskets and the head gasket replaced. Yesterday when putting new plugs in i noticed that the same 2 plugs had oil on them, the other 2 plugs were fine. I am not burning oil (no smoke of any color from the exhaust) i only add about 1 and 1/2 quarts every oil change or every 6k miles. I switched to synthetic oil about 18 months back. Could the thinner synthetic be easing past the rings? I get almost 30 mpg around town so i have not lost any mileage. Thanks

Year and mileage? 1-1/2 quarts in 6,000 miles is considerable. You only change your oil every 6,000 miles? If it's not leaking oil, it's burning it possibly from leaking valve seals, and probably mostly at piston rings. Was oil on the two passenger side spark plugs?

Is this on your 1998 Corolla you posted before in the past? That had some oil consumption issues - something on the order of 1 quart every 5K miles? Seems to have gotten a little worse.

Head gasket replaced? Did you mean to say the "valve cover" gasket (or did you really mean "head gasket"? I believe that was mentioned in an older post, can't remember off the top of my head. If it was the head gasket - why was it replaced, overheated? That would be a completely different situation entirely.

If it was the valvecover gasket - possible the valvecover bolts has lossened up. I usually like to double check those bolts atleast once a year - make sure they didn't loosen up. More so immediately after replacing the valvecover gasket and then about 500-1000 miles later, to make sure there is a good seal. Guard against overtightening them - as the gasket is the o-ring type - seals best when the o-ring is not completely deformed (ie, squashed flat).

If this is happening more often - after installing a fresh set of plugs - check them after a couple of hundred miles, see if there is any oil on them. Take note of what cylinder they came out of. Clean the off, or install another set - check again. See if there is a pattern. If there are specific cylinders that are consistently wetting the plugs - I'd do a compression test (both dry and wet, to see if the measurements change - also do a leak down test to check the valve seals). See if there are cylinders that are out of spec.

Oil on the spark plug electrodes could not be from a leaking valve cover gasket... I believe he means oil at the firing end of the spark plug.

Yeah, I was think more along the lines of a leak around the spark plug tubes from a faulty o-ring. Oil can seep past the threads and down to the plug end.

Could also be a misfire / intermittent ignition - causing the plug to load up with gas/oil/combustion gases - making it look wet at the tip. Also, if the plugs are dripping with oil - could be a blown headgasket, completely stuck piston rings.

friendly_jacek

The last time i changed the oil, i noticed oil on the tip of the spark plugs, i had new plug gaskets and the head gasket replaced.

The OP should come back and clarify where exactly oil on plugs is located and what exactly gaskets were replaced. The info, as presented above, makes little sense to me.

Hi Fish and the rest of you for answering my post. Yes i did post about 2 years back for the same problem. Bought the corolla new, now has a little over 210,000 miles on it. I now use synthetic so am told that changing oil every 6,000 miles is well within the time frame. Using dino oil i changed every 3000 miles.. Oil was only on plugs 1 and 2 (i am counting left to right when facing the firewall) Fish, sorry about that, it was the head cover gasket that had to be replaced because of the job involved. Also it was the firing end of the plug. I use the plug that has 2 points at the firing end as recommended in the manual. I was also thinking the o-rings may have been misinstalled according to material i had read. What really baffles me is that i still get about the same mpg as before i noticed this problem Thanks to all who answered. Bobbiw.

Yes, oil on firing tips of spark plugs #1 and #2, as I had suspected... It's from oil burning, mostly at piston rings, beside at valve seals. It would be better with high mileage oil which has slightly higher viscosity and is formulated for worn engines with seal conditioners as well. Beside Mobil 1 synthetic high mileage oil, Valvoline has MaxLife high mileage oil available in synthetic. Quaker State Defy semi-synthetic is richer in ZDDP (zinc).

http://www.mobiloil.com/USA-English/MotorOil/Oils/Mobil_1_High_Mileage_5W-30.aspx

http://www.mobil.com/USA-English/Lubes/PDS/NAXXENPVLMOMobil_1_High_Mileage_Oil.aspx

http://www.valvoline.com/products/brands/maxlife/full-synthetic-motor-oil/3

http://www.valvoline.com/pdf/maxlife_full_synthetic.pdf

http://www.quakerstate.com/#/motor-oil/defy

http://www.epc.shell.com/Docs/GPCDOC_X_cbe_24855_key_140007079157_201203220840.pdf

friendly_jacek

I don't understand that. Severe oil burning can produce plug fouling, but by ash like substance and not wet oil. I had some minor oil burning, but plugs always looked great.

I agree with the HM oil suggestion, but piston soak would be also a good idea to fix/decrease the consumption while still mild.

I just fixed the same problem on my car. Check the seals around the inside of the spark plug chambers, where the valve cover meets, could be seaping in from there... hope this is enough to solve your problem. Good luck and tell me after fixing it about your car's condition.

Yesterday, I changed spark plus on my 1999 Corolla (132K) and I found oil on two spark plugs on passenger side.

I was going this forum; but did not get the instructions, what to check and what to replace, I hope you guys to help me; what will be process to check and to be done. I will appreciate if there is any linked video. Again thanks guys for all your help.

Oil on the electrode (bottom part of plug) or on the spark plug body?

Try looking down the spark plug well for those two plugs and see if you see any oil pooled inside the well. If there is - oil could be leaking from the valvecover and/or plug well gaskets - pretty common once you get up to this mileage and age of car. Could also be from plugs that were not fully torqued down into the cylinder head - could cause oil to wick up the threads of the plugs.

If the oil is on the very tip of the plug - could be from a number of different sources. Can be as simple as heavy fuel dilution, where the injectors not spraying fuel evenly or cleanly into the plug well - thinning out the oil, making it more likely to get on the end of the plug and have enough material to coat the plug enough to wet it.



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