I have a 2001 Toyota Siena, and it has suddenly started losing oil, but my mechanic can’t figure out where the oil is going. There is no smoke coming out the tail pipe, and no leakage apparent anywhere. It is losing half a quart of oil every 200 miles. Shortly after this problem began, the check engine light came on, and the diagnostic machine indicates a misfire on the second cylinder, but no misfire is apparent when my mechanic drives the vehicle. What could be going on?
There may be oil coming out of the engine but between it depositing on the cat converter honeycomb and the oxygen sensors, along with dispersion through the air from movement, you may not be able to see it.
The misfire could be coming from a fouled plug or perhaps even a fouled oxygen sensor, although that should store additional codes. Any good shop can and will look beyond the codes and the test drive to solve the problem.
Sorry, but this is enough oil to be readily diagnosable. Perhaps another shop can do better.