Q: does a cracked exhaust manifold cause oil to leak

A damaged exhaust manifold does not affect engine oil consumption. Of serious concern though is the possibility that the cracked manifold is leaking exhaust gas (including poisonous carbon monoxide) into the passenger cabin, typically through the firewall and vents. If the manifold is leaking exhaust gas, I do not recommend driving the car because carbon monoxide is really, really bad for the body. Most deaths and injury from carbon monoxide are NOT from the acute incidents of poisoning deaths that you read about in the newspaper. Rather, the vast majority of mortality and morbidity due to CO poisoning is due to long term exposure to low levels such as driving a car with an exhaust leak under the hood. CO exposure is very bad for body tissues and again the problem is these sub-lethal, but chronic exposures that people do not think about. Most people think the problem with CO is the acute incidents and don’t give adequate consideration to the well documented negative health impact of the sub-lethal chronic exposures so get the cracked manifold repaired right away for the sake of your health!! If you want to schedule that, simply contact YourMechanic via the website inquiry form or telephone the YourMechanic toll free number. With regard to engine oil, you should add enough oil to bring the level to the full mark on the dipstick. Monitor your oil consumption. If the engine is using a lot, you might benefit from replacement of the valve stem oil seals and/or you may have oil leak(s) that can and should be fixed. Please let us know if you have any additional concerns.