Downshifting a manual transmission to the point of MECHANICAL over-revving might very well damage the engine. Over-revving the iCE to such a level is an engineering impossibility. The HSD control computer would not allow that level of roadway "drive" to reach the ICE.

So, not to worry, while the ICE may sound loud/noisy there is little or no potential for ICE damage.

If you apply the brakes in order to slow down and the hybrid battery is already at full charge then the system will revert to frictional braking. I would think that allowing the HSD control computer to manage the overall braking would be the proper method.

With a hybrid YOU WANT the hybrid battery to be charged whenever the computer thinks charging is appropriate. So IMMHO the proper procedure to us is to let the system do the "driving". Put the system in "B" and if that doesn't provide enough engine compression braking AND regenerative braking combined then simply step on the brake pedal.

On the other hand it is entirely possible that your best FE would be attained by NOT used "B" but using the brake pedal. With use of the brake pedal the BEST, quickest, hybrid battery recharge will take place and frictional braking to suppliment as needed.

Personally I would only use "B" once I noted that the hybrid battery was charged at some level I considered optimal.

I don't know, have no idea if this would work, but try using cruise control to hold the road speed down to the level you wish. CC might have more speed "restraining" capability (almost for sure automatic regenerative braking) in the hybrid than in an ordinary car.

 

I use for Breaking. In my 2010? Highlander Hybrid. I use it like a compression gear., I have. 155000 miles on my 2010 and have not needed to change brake pads . I also use d gear for everything except slowing down.