[RH77]

I have a similar inquiry regarding premium...

Since premium comes at a, well, premium these days, we're wondering if we should try mid-grade and/or regular in the '06 TSX due to the inflated costs of this fuel (manual says "Premium Recommended"):

Engine Code: K24A
Compression Ratio: 10.5:1
Power: 205 hp (150 kW) @ 6800 rpm
Torque: 164 ft·lbf (222 N·m) @ 4500 rpm
VTEC Engagement: 6000 RPM
Redline: 7100 rpm
Current # miles: ~36,000

FE is ~30 mpg for a calendar year, running premium, minimal technique. We tried a controlled experiment one Winter, but the temperature fluctuations were too erratic for good results.

My concern is that the timing will be retarded to the point of drop in FE. More pollutants is not the aim. We honestly don't need the engine's full potential. The reason we bought it was for the 4-cylinder in this vehicle class.

I have an OBD-II datalogger that can be hooked-up to store the following parameters with vehicle speed as the mandatory 5th paramater for a total of 4 optional at one time:

Engine Speed
Throttle Position
Coolant Temperature
Engine Load
Air Flow Rate (not supported)
Intake Air Temperature
Intake Manifold Pressure
Fuel Pressure (not supported)
O2 Sensor Voltage (up to 8 monitored)
Ignition Timing Advance
Short Term Fuel Trim (up to 2 monitored)
Long Term Fuel Trim (up to 2 monitored)
Battery Voltage

It's equipped with a knock sensor, so it would likely retard timing.

Since the last test, I found it was possible to calculate FE based on OBD parameters.

Finally, The Question:
Which parameters to choose?

RH77