Dry Start
Starting an engine after it has been sitting long enough for oil to drain from critical parts, causing brief metal-on-metal wear.
A dry start refers to the initial seconds of starting an internal combustion engine when oil pressure has not yet built up, and internal parts lack sufficient lubrication. This condition typically occurs after a vehicle has sat idle for several days or weeks, allowing engine oil to drain out of the oil galleries and away from upper valvetrain components back into the oil pan.
During a dry start, components like camshaft journals, rocker arms, and crankshaft main bearings experience brief metal-on-metal contact. While modern engine oils leave a microscopic protective film, it is not enough to completely prevent friction wear under cranking loads. Anti-drainback valves inside oil filters are designed to mitigate this by keeping oil trapped in the upper engine passages.
Symptoms of dry start wear include a brief tapping or clattering noise immediately after the engine fires, which disappears once the oil pressure light turns off. Installing high-quality oil filters with silicone anti-drainback valves and using synthetic oils with superior cling characteristics helps prevent dry starts. In extreme cases, oil accumulators are installed to pre-pressurize the oil system before cranking.