The title says it all. A friend brought it up - when flooded, is there a risk that gas goes back into the oil and should I change my engine oil now? Or am I safe because the oil is injected?

I did a search for "Flood oil change", found many threads but no answer.

Peter

 

Yes, it would be a good idea... you're going to have some fuel dilution in your oil.

 

No, an oil change is not necessary.
On a piston engine the fuel in the cylinders runs down into the oil pan and dilutes the oil.
On the rotary engine, the cylinders (rotor housings) are isolated from the oil pan, so the fuel just stays in the housing (which is why they flood, vicious circle...)

 

Well any time an engine is flooded fuel will seep past seals (and rings) and mix with the oil whether on a rotary or not. The rotary will carry the liquid fuel up over the center of the eccentric and then fuel will seep past the side seals into the eccentric shaft and mix with oil there.

 

Rotary Nut, if a rotaty is flooded then there is very little fuel getting carried anywhere because there is no sealing at the apex seals. The fuel just sits at the bottom of the rotor housing, forming a bath for the apex seals to wash all their oil off in. Some gets transferred, or splashed up around the housing by the rotation of the rotor, but very little will make it above the center line of the eccentric shaft, and then down the side of the rotor past the side seals, cut-off seals and oil seals into the oil drain cavities of the rotor (I say above the center line of the rotor because the feed of fuel into the oil drain cavity would be gravity fed).

Understand? This is not my opinion, it is physics...

To answer the question again, No, you do not need to changed the oil after flooding.
Maybe the cat though...

 

ptiemann,

This article is for an RX-7, but I bet the quoted part applies to our RX-8s:

http://www.rx7.com/techarticles_unfloodFC.html

"If car is heavily flooded, spark plug replacement and oil changing may be required."

"It is highly recommended to change the oil as soon as possible. Oil becomes heavily gasoline contaminated from the flooding."

 

The Renesis engine does not flood as badly or as often as the engine covered in this article. Only a small amount of fuel would find its way into the lubrication system, but with constant oil top ups this would not really dilute the oil much. If the engine has flooded repeatedly it may be a good idea to change the oil though.