If your vehicle is showing puff of blue smoke from the exhaust on cold startup, here are the most likely causes and the parts you'll need to fix each one.
Over time, the rubber seals on the engine valves harden, crack, and shrink due to heat cycles. When the engine sits overnight, oil from the cylinder head seeps past these worn seals into the combustion chamber and burns off as a puff of blue smoke upon startup.
A stuck PCV valve or clogged oil separator allows excessive oil vapor to be drawn into the intake manifold. This oil pools in the intake while the engine is off and gets sucked into the cylinders and burned immediately on startup.
If the engine had recent cylinder head work, the delicate valve stem seals may have been torn on the valve keeper grooves during installation, improperly seated, or installed without protective sleeves, causing an immediate oil leak.
On turbocharged engines, worn internal seals or a restricted oil return line can cause oil to pool in the intake or exhaust piping while parked. This pooled oil burns off as a cloud of blue smoke when the engine is started.
The metal guides that keep the valves straight can wear out, creating excessive clearance. This allows the valves to wobble, which stretches the valve stem seals and allows oil to bypass them into the combustion chamber.
While worn rings typically cause continuous blue smoke while driving, severe wear can occasionally allow oil to seep past the rings into the combustion chamber while the vehicle sits, contributing to startup smoke.