Recently bought a 2015 350F with 55k miles. And got it to 60k in the first two months or so. Did my spark plugs today as recommended for 60k and discovered oil on the threads of only one plug, the passenger side plug farthest to the rear… the one right under the throttle body. The rest were dry. Immediately noticed that plug broke loose much easier than than the other five before I even got it out. Looked down the tube with a flashlight and saw a little ring of oil where the crush washer/gasket was however the outer hedge of that surface was completely clean, so the oil is coming from inside that cylinder for sure. The threads were not completely drenched but I did notice there was a little bit of oil between the threads when I removed it, should have taken a picture before I wiped the threads off but you can see it is in fact oil on that rag in the pic. Think this may be a common thing with IS’s? Maybe related to the IS’s propensity to burn a little oil? I read another thread that concluded that having oily threads on both rear plugs on IS F’s is pretty normal and nothing to worry about. But didn’t find much in the 350 engine specifically. One other thing I’ve noticed is that my exhaust tips do have a good bit of carbon build up on them but my old IS250 that burned acceptable amounts of oil had that as well. Did the first oil change two weeks ago and noticed there was exactly 5 quarts of oil left in the car and that it was hitting the bottom dot on the dipstick so I filled it up to the top dot knowing about the oil burning thing which is about 7-7.5 quarts. Should I be concerned? Car runs great otherwise.
It could be a number of things, really. It could be that the spark plug was never really tightened right and was not giving a tight seal. I wouldn't worry much about it, just clean it out down there and put the new plugs in. If you're really concerned, give it a few thousand miles and check that spark plug again.
Wouldn't even worry about...put the new plugs in and keep on trucking. The amount of oil was so small it literally could be anything, and honestly not even really a concern.
As @Yri suggested, recheck in a few thousand miles to confirm it's wet or dry.
I bet it's related to design since same exact plug was wet on the threads during my last two plug changes (15MY IS350). I also read on here of another member noticed the same thing.
I'm at 135K as no noticeable side effects so I'm not worrying about it anymore.
Recently bought a 2015 350F with 55k miles. And got it to 60k in the first two months or so. Did my spark plugs today as recommended for 60k and discovered oil on the threads of only one plug, the passenger side plug farthest to the rear… the one right under the throttle body. The rest were dry. Immediately noticed that plug broke loose much easier than than the other five before I even got it out. Looked down the tube with a flashlight and saw a little ring of oil where the crush washer/gasket was however the outer hedge of that surface was completely clean, so the oil is coming from inside that cylinder for sure. The threads were not completely drenched but I did notice there was a little bit of oil between the threads when I removed it, should have taken a picture before I wiped the threads off but you can see it is in fact oil on that rag in the pic. Think this may be a common thing with IS’s? Maybe related to the IS’s propensity to burn a little oil? I read another thread that concluded that having oily threads on both rear plugs on IS F’s is pretty normal and nothing to worry about. But didn’t find much in the 350 engine specifically. One other thing I’ve noticed is that my exhaust tips do have a good bit of carbon build up on them but my old IS250 that burned acceptable amounts of oil had that as well. Did the first oil change two weeks ago and noticed there was exactly 5 quarts of oil left in the car and that it was hitting the bottom dot on the dipstick so I filled it up to the top dot knowing about the oil burning thing which is about 7-7.5 quarts. Should I be concerned? Car runs great otherwise.
late to the party but changed my spark plugs on my 06 is 350 today. All had a slight amount of oil. By slight I really do mean barley any. The middle plug on the passenger side was identical to yours by being more wet than the rest. But my car has 185k miles and still running strong. Was kinda spoked but as people are stating this seems normal for our cars
Recently bought a 2015 350F with 55k miles. And got it to 60k in the first two months or so. Did my spark plugs today as recommended for 60k and discovered oil on the threads of only one plug, the passenger side plug farthest to the rear… the one right under the throttle body. The rest were dry. Immediately noticed that plug broke loose much easier than than the other five before I even got it out. Looked down the tube with a flashlight and saw a little ring of oil where the crush washer/gasket was however the outer hedge of that surface was completely clean, so the oil is coming from inside that cylinder for sure. The threads were not completely drenched but I did notice there was a little bit of oil between the threads when I removed it, should have taken a picture before I wiped the threads off but you can see it is in fact oil on that rag in the pic. Think this may be a common thing with IS’s? Maybe related to the IS’s propensity to burn a little oil? I read another thread that concluded that having oily threads on both rear plugs on IS F’s is pretty normal and nothing to worry about. But didn’t find much in the 350 engine specifically. One other thing I’ve noticed is that my exhaust tips do have a good bit of carbon build up on them but my old IS250 that burned acceptable amounts of oil had that as well. Did the first oil change two weeks ago and noticed there was exactly 5 quarts of oil left in the car and that it was hitting the bottom dot on the dipstick so I filled it up to the top dot knowing about the oil burning thing which is about 7-7.5 quarts. Should I be concerned? Car runs great otherwise.
I had exact same "issue". It was plug number 5 or 6... I brought it up with lexus rep and she said it is fine. In some severe cases they have to change the gasket but there has to be a code thrown. If no codes are present, the amount of oil is not superlarge... So, just keep driving,
