Oil Catch Can, Anyone?

In the Gen III Prius, an oil catch can definitely prolonged engine life, because it traps oil which would otherwise be drawn into the engine's intake. Because the Prius is direct-injected, this oil is not washed off by the gasoline and the intake and valves get coated with oil. The oil burns in the combustion chamber, and it then gets blown into the catalytic converter and into the EGR, where it can foul the EGR cooler and EGR valve.

With our 2026 Prius about to arrive, I wanted to know if anyone's installed an OCC on theirs.

At first, I thought the PCV was the big hose on top of the engine, leading into the air intake. But then I checked the service manual, and found that it routes into the throttle body. It is Item 10 in the picture below, and not *3, which I had first thought.

 

Update: It appears impossible to install an oil catch can on this engine. The PCV valve vents directly into the intake manifold, without any hose whatsoever. To access the PCV valve, you must remove the intake manifold.

 

But the Gen III still had substantial problems caused by the PCV delivering oil into the air intake. Even with port injection cleaning off the intake valves, you still get burnt oil in the exhaust, which leads to a clogged EGR and damage to the catalytic converter. This lead to head gasket failures on the Gen III.

With this engine, we will need to remove the intake manifold periodically to inspect for oil build up. Or, perhaps we can remove the EGR pipe to inspect for oil deposits. I don’t have the car yet, so I haven’t been able to assess what’s needed, if anything.

 

Yes, the PCV sits much higher than it did on the Gen III engine, which is a big improvement. In a Gen III Prius, it was standard to see about two tablespoons of oil pooled beneath the throttle body, on any model. We will need other inspection and remediation measures, like EGR cleaning, if oil gets through the PCV.

 

If the engines were the same, then we would already know that a catch can is necessary. It is easily proven, because you can pull the air intake off the throttle body of any Gen III Prius, open the plate, and you’ll see a puddle of oil. It’s always there and it gets there from the PCV. For sure. The other factors you mentioned are also possible, but for sure the PCV is a problem.

This gets us to the other point: We do not know if oil is entering this engine from the PCV. Maybe it does, maybe it does not. Because of its design, it may be difficult to determine.

 

I bet you no longer get a puddle of oil in the throttle body.