The simple reality is, it's either leaking or burning. If you can't find a leak, it's burning at a slow enough rate that the catalytic converter is burning it before it goes out the exhaust as smoke.
Note, however, that condition will quickly change once the converter is fouled, then you get to purchase a new engine AND a catalytic converter.
You're Leaking Gas into your oil
Oil is leaking and burning off due to a gasket failure. Replace it or you're in for a world of costly repairs
where is it leaking from?
If it is CFI, the fuel pressure regulator could be leaking fuel. If the check engine light is on, have the codes read.
your heater core is leaking
usually caused by a leaking heater core.
Mine is doing that too. Almost seems like its getting into the transmission. Please re-post if you find anything
its the PCV valve
The heater core has failed and is leaking engine coolant.
If your vehicle is leaking fumes, then your gas tank needs to be fixed.
transmission fluid
could be freeze plug, or intake leaking