Hi I've just a week ago bought a bmw 320i coupe 2007 reg and I experienced a few misfires and an eml light came on I took it for a diagnostics and was told that there is possibly an issue with the thermostat or catalytic converter however the errors were cleared and than nothing came up. Recently another warning light has come which disappears after a few seconds and I can still feel the engine misfiring I've gotten it checked out by the local mechanic who opened the coolant cap to find oil in the coolant reservoir however this fluid doesn't smell or have the same density as engine oil and feels more like grease. My question is wether it is a head gasket problem? Ie a possible leak? And if it is how much am I looking to pay to get it fixed? Please help as this is my first bmw and I don't want this to be a bad experience!