[jfjohn]

About how much lower is the gas mileage in my 96 taurus gl when it is cold and warming up but still in open loop?

[Graybeard]

You could run a tank of gas with the oxy sensor disconnected, and let us know. . .

Oh, to really simulate the condition, you would need to remove the thermostat. I'd estimate a drop like 30%.

[MichaelJennnings]

Originally Posted by jfjohn

About how much lower is the gas mileage in my 96 taurus gl when it is cold and warming up but still in open loop?

Most cars of this age actually didn't stay in open loop mode for very long unless you are sitting at idle in a very cold area. Most of the time, the car would reach the 160 degrees needed for closed loop operation very quickly. As for fuel economy, like mentioned, it is probably be around a 30% reduction.