Oil in number 1 cylinder, fouling out plug - 1997 Saturn SL

I am assuming it is oil fouled rather than fuel fouled. Oil fouling is usually due to valve stem seal leakage. Most engines have the oil return on the cylinder head at the rear. When the engine is shut off, some oil pools at the rear of the head. If the valve guide seals are worn, then the oil will leak around the stem of the #4 valve and eventually foul the plug. If there are no real issues with the engine other than this one, it is usually best to keep a clean plug or two available and swap out the plug periodically when fouling is detected. Then clean the fouled one and keep for reuse later. If it is happening too often, getting the cylinder head reconditioned is a good idea.

Oil in the cylinder(s) can foul plugs, resulting in misfiring and thus loss of power. Another possibility is that the oil in the cylinder(s) comes from oil leaking into the cylinders. If these leaks are of sufficient size, they will reduce compression in the cylinder, and thus reduced power upon the cylinder firing.

the next time it fouls check the plug when you take it out, if it is covered with oil then you may have a broken ring on the cylinder that is allowing oil to pass through to the combustion chamber and fouling the plug. Or the valves pay be letting oil drain in past the valve seats.

You need to have the rings replaced. Do the compression check again on a cold motor with this exception, add a small amount of oil to each cylinder. First do the test on the cylinder and record the pressure then add a small amount of oil and redo the test and compare the compression. I am attempting to identify if the problem is rings, valves or head gasket. I am concerned about cylinder 1. The compression is within range however the readings you provided indicate uneven compression. If after you add the oil the pressure evens out across the cylinders the problem is rings. If you get the same readings during both test the problem is the Head Gasket or a need to have a valve job done. The fouling is caused by oil getting past the rings or seals. Use regular oil in this test preferably in a hand oiler. Two to three squirts should be enough. DO NOT USE WD40 OR OTHER SPRAY LUBRICANTS. Those will damage your cylinder walls.

Was the plug fouled again after you made repairs? Did you install a new plug and run it? If the plug itself is fouling you probably also see blue smoke in the exhaust pipe. Get the engine warm, check compression and do what is called a cylinder leakage test, it puts a volume of air into each cylinder with the valves closed and how much air leaks out determines the over all health of the engine. Does the engine have excess oil consumption? The oil entering the cylinder and fouling the plug can enter from a worn valve guide or guide seal, a worn or damaged oil control piston ring or a worn or damaged piston bore or piston, none of which are going to be inexpensive to fix.

Good luck, i hope this helps.

If the insulator was cracked the plug would have been misfiring, unless it was broken while trying to remove it. If this oil fouling is an ongoing problem, and you have to keep changing the plug, buy a spark plug that is designed to fire when oil fouling is a problem. You may have to order one from a part catalog, such as JC Whitney. This would keep you going until you can get the problem repaired..

possible causes of oil fouled spark plugs include bad/worn valve stem seals, worn or scratched cylinder walls, broken /leaking piston rings

The most common cause for oily spark plugs are worn rings in that cylinder or valve guides. Have compression check done on your cylinders to verify if the #6 cylinder has low compression. If compression is low only recourse is to have the engine overhauled.

these were bad for the spider injectors to fail. they are hard to diagnose with out the scan tool. the poppets in the end of the injectors get clogged and will need to be replaced. pull the plug and see if its oil fouled. they also have a problem with the #1 cyl getting out of round and oil fouling the plug. compare it to another plug in the engine. if its oil fouled the engine is no good.

Check your distributor cap & wires first. If all is ok pull the spark plug and check if it's oil fouled. If there is no oil on the plug the plug might be bad. if there is oil on the plug you can get an adaptor that screws over the end of the plug and shields it from getting oil fouled. Of course this is a temporary solution for a piston ring or valve seal problem. I had a caddy I ran with plug shields fo 5 years so they work! Good luck!....PS If your plug is oil fouled you can also use a heavier oil like a 20/50 or use 4 quarts of 10/40 and a quart of lucas oil stabilizer. This will help keep the oil where it belongs and don't forget to do an oil change every 2,500 to 3000 miles.