Thanks. I did notice that
Thanks. I did notice that the tire wear rating for the OEM tires was a healthy 520.
Let me start out
Let me start out with, the negative split mode is when the small generator/motor/starter uses energy to control the engine RPM. This energy is not totally wasted because it is reducing or controlling the RPM of the engine. In other words, the generator is taking stored energy from the battery and not providing energy to the traction motor or HV battery. Out of the other modes of operation, this is the one least FE. Positive split mode is when the generator is charging the battery and provides energy to the traction motor for torque boost.
As far as the HV battery being full, there are 2 limits. The first limit is full at around 52% when the small generator/motor/starter stops charging the HV battery. The exception is when the computer conditions the battery with over charging for protection of the battery life. The second limit is 60% and this is the room the designers made for regen charging. In other words, charging above 52% is reserved for regen from the traction motor. Understand that regen charging occurs while driving in "D" or "L", even without applying the brake pedal. This is why coasting in "N" is ~36% better than "D", "N" eliminates regen completely and you have no traction motor drag.
When the small generator charges to its limit of 52%, the generator starts to control engine idle at highway speeds. This is when negative split occurs. To avoid negative split during this condition, I've concluded shifting in and out of "N" at highway speeds (P&G) with a full HV battery stops the negative split mode. During "N" coasting, the engine idle is controlled by the engines PCM, and not the generator (battery powered). This idle is called the secondary idle and is most often a higher RPM. Instant MPG can drop on the SGII from just coasting in "D", but remember your coasting 36% better and longer. Using this technique combined with drafting at a safe distance, can yield better than 45mpg at 65-70mph.