What happens if you preform an oil change on a vehicle using synthetic oil and you use regular motor oil?

Is it possible that it could ruin gaskets around the cylinders causing them to leak oil onto spark plugs? It's an older vehicle (89 Civic Si with a ZC engine swap)





Just wondering what would happen, im trying to diagnose what the problem is currently its leaking oil into the cylinders after an oil change! :(What happens if you preform an oil change on a vehicle using synthetic oil and you use regular motor oil?
Synthetic or regular motor oil is immaterial, they can even be mixed without any bad effects...





';Leaking'; onto the spark plugs? Outside, ';on top'; of the spark plugs, is a valve cover gasket most likely. ';oil soaked'; plugs when you pull them out, can be cracked or broken valve, bad rings, or bad head gasket.





Try a compression test once, then with oil squirted in each cylinder, that will help check for rings. Valve seals you'll have to pull the valve covers to visually check...





Head gasket, pressure test your cooling system for one.What happens if you preform an oil change on a vehicle using synthetic oil and you use regular motor oil?
If the oil burns on acceleration then the rings are bad. If it burns after you let off the gas then the valve guides are bad.
No problem at all. Get all the old oil out (as much as possible), and adjust your change interval accordingly.
all depent on ,who did the change?


YOU or the MECHANIC???





same oil numbering?


most of the mechanics,in the internet will say,it's not a big deal to change the oil.





well!!!..........yes it is!!!!
You might have needed a valve cover gasket for a while. While it's possible that switching oils might affect seals; I've switched from Mobil One to regular oil with no problems. I would attribute it to the age of the car. After a while the seals are going to leak. The gasket shouldn't be that hard to change or expensive.
how are your valves. the oil itself wont cause a problem but if the seals are worn then you could have a problem. might be time to pull the top half of the engine off.
It depends on how many miles your car has....if the gaskets have hardened and synthetic oil is introduced...it may -resoften them and cause leaks....





The truth is, if you already have some very small leaks...Synthetic oil will seep through those cracks much faster due to its commutative properties...the molecules are much smaller....and are thus more prone to penetrating small crevices.
when synthetic and regular oil are introduced to eachother they create very high pressure that results in gasket failures. i doubt that it could have an effect on the head gasket, but for sure it can on the oil pan gasket and others seals in the crank case. best not to change to different oils in an engine. just give it one kind for life is best i believe.
You probably have a worn out engine (worn rings or valve guides/ seals). Thats the only way oil gets into the cylinders.





Do a compression check.
no you cant ruin the cyl head gaskets as they dont come in contact with motor oil unless the piston rings are gone. if you have oil leaking into the combustion chamber its the valve guides. changing from syn oil to reg oil makes no differance. #2, if your oil filler is in the valve cover then it is the valve guides!
If you PREFORM an oil change, then you have not really formed it yet.