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I was at steady state highway travel about 58mph in 4th gear.
The readings were off the scamguage.
The motor was warm and in closed loop
Previous experience has shown that in open loop my FE on the highway is about 27mpg (don't ask how I know)
It appears that when my timing at highway speeds (again previous experience) is in the 20's my fe is the same as open loop which also has timing in the 20's
I have had experiences across the board on different vehicles where fuel economy would drop for no apparent reason and stay there while lightly feathering throttle going down a hill to maintain speed. In those cases however I could let off the gas and wait for the GPH meter to bottom at idle rates then my FE would go back up.
I have sometimes heard of this called detroit fever or a long term correction.
From what I have learned the motor tries to operate at stoich but very rarely does except on the highway at steady state and even then few motors actually operate at true stoich but usually a few degrees below, exceptions being very modern motors. Even light acceleration usually drops you out of stoich.
Also note is was quite cold, many motors go a bit excessive on timeing & A/F corrections when it is cold thus why many suffer MASSIVE FE reductions even on long trips, couple that with "winter gas" and you have a craptaskic combination.
Cheers
Ryan
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