Prius start consuming excessive engine oil

yikes, sounds like a blown engine. get that checked immediately

 

What does "excessive" mean? What is the oil consumption per 1,000 miles?

If you can see visible exhaust emissions, that is not good. The possible problems include worn piston rings or piston bores, which can be checked by performing a cylinder leak down test; or leaking valve stem seals or valve guides, which will not be revealed via the leak down test.

How long have you owned the car? If not very long, it is possible that a prior owner abused the engine by allowing the oil level to drop below the bottom dimple on the dipstick, thus causing abnormal engine wear and accelerating the rate of oil consumption.

 

One liter every 2400 miles is not excessive consumption. You have absolutely nothing to worry about. Just check your oil every other time you fill up the fuel tank.
5W-30 is the spec viscosity.

 

Your first post has misleading wording and it sounded like there is a lot of smoke in the exhaust. If English is not your first language, this is understandable.

Many Prius cars start consuming oil at that rate around 150K miles. Mine did. Yours at 120K is a little early, but not unusual.

 

My 2006 Prius has had a mysterious oil burning issue forever. Burns oil but does not leak on the ground, on the engine or anywhere else. just gone. They said change the engine or check & fill the oil more often. HMMMM, So now I carry oil with me and try to remember to add a quart every week or so. It is a hassle but much easier- cheaper fix than a new engine. Costco carries a case of oil quite reasonably.

 

how many miles per quart?