Is factory ignition timing for sea level?

[Tburn7]

Curious, but just want to verify that factory ignition timing numbers are for sea level. I'm assuming so, but the tag under my hood (ea82 TBI) does say 20*BTDC +/- 2* (in green connector mode).

 

Why the range if the ECU controls/adjusts fuel and timing while running? I'm guessing it's for altitude compensation. I'm at around 4,600' elevation.

 

I can't really expect much for "performance" enhancements with this engine, but enhancing fuel economy is always a plus.

 

I'm running about 18*BTDC right now, I think next fuel-up I'll advance to 20* and then to 22* on the following tank and see if the difference in MPG's and/or performance is appreciable.

 

Cheers!