I installed a nifty air/fuel ratio meter on my 92 Volvo 740. Before\nit goes colsed loop, it read 17.0 and pretty stable. It is obvious\nwhen the car goes closed loop, as it then varies a lot. It takes a\nmeasurement of the O2 sensor about once a second. I noted, at idle,\nthat the high is 19.5 and the low is 14.3. But it might be a false\nassumption to take the median value as the average mixture reading...I\ndon't know. I see that Chevron says that stoiciometric for regular\nunleaded gas is 14.7...at least for their brand. But I would think\nthat all gas would be somewhere close to this. SInce the low reading\nis so close to 14.7, and the high is so much higher, I am thinking\nthat it is showing a lean condition. THe instructions that came with\nthe gauge don't tell you how to interpret the readings! But the gauge\nis clearly marked AIR/FUEL. So I think it is saying the air/fuel\nratio is X parts AIR relative to 1 part fuel. But the way my Volvo\nwagon eats gas, I SERIOUSLY doubt it is actually running lean!