According to Lyle wossname the way they work out 230 mpg is - start with full battery and fuel tank. Run in city cycle as EV until the engine kicks in. Run one more (11 mile) cycle under charge sustaining mode. measure fuel used. then mpg = (EV miles+11)/fuel used. I'm not saying that's right, or even justifible. I don't know where the 150 number really comes from and to my mind it confuses the article, you won't get 150 once itis in charge sustaining mode. That shows the danger of using the general press as references, they really mangle every statement even if the interviewee is not misleading tham.