Here's a breakdown of why:
* Gas in the oil: This indicates that fuel is getting past the piston rings into the combustion chamber. This is a serious issue because it can contaminate the oil, causing it to lose its lubricating properties, leading to engine damage.
* Black smoke from the tailpipe: Black smoke is usually a sign of burning fuel. Since the fuel isn't fully combusting, this points to a problem with the fuel/air mixture. The fact that the fuel is making it into the oil (as shown by the gas in the oil) indicates that it isn't fully burning in the cylinders.
* Surging: The surging likely results from inconsistent fuel delivery and combustion, a direct consequence of the fuel leaking past the piston rings. The engine is misfiring, leading to an uneven power output.
Possible Causes:
* Worn piston rings: The most likely culprit. Over time, piston rings wear down, losing their ability to create a proper seal between the piston and the cylinder wall. This allows fuel and combustion gases to leak past.
* Worn valve seals: Worn valve seals can also allow fuel to seep into the engine, contaminating the oil.
* Cracked piston: A less common but more severe issue. A cracked piston would allow fuel and combustion gases to escape into the crankcase.
* Head gasket failure (less likely, but possible): While a blown head gasket can lead to gas in the oil, it would typically also cause other symptoms like overheating, white or milky oil, or loss of coolant. The black smoke and surging make a head gasket failure less probable than piston ring issues in this scenario.
What to do:
This is a serious problem that needs immediate attention. Continuing to drive the car could cause catastrophic engine failure. You should:
1. Stop driving the car immediately. Continuing to drive it will worsen the damage.
2. Have a qualified mechanic diagnose the problem. They will need to inspect the engine to determine the precise cause and recommend the necessary repairs. This will likely involve an oil change (with careful disposal of the contaminated oil) and potentially an engine rebuild or overhaul.
Ignoring this issue will lead to further damage and potentially a costly repair or engine replacement. Get it checked as soon as possible.
