Shortly after purchasing my 2018 US PHEV (GT trim level) new, I too noticed the burning rubber smell after I drove on the I-5 freeway at 60 to 70 mph with 4WD Lock on, in Charge mode, with braking regen strength B5, attempting to quickly charge the battery pack.
Soon thereafter I needed to replace my rear electric motor’s rubber motor mount (motor mounts? I don’t know if there’s more than one). The mount(s?) were entirely missing. I presume they shriveled so much from being burnt that the carbonized remnant(s?) simply fell out. The absence of the rubber mount(s?) made the rear end go “clunk” when starting off from a standstill.
Now, please realize, I do not know for certain that the rubber rear motor mount(s) was/were the source of the burning rubber smell. Maybe something inside the battery case or elsewhere was overheating. The motor mount(s) is/are just my best guess.
So, from then til now, on the freeway I either keep it in D (= regen strength B2) or else, on long downhill stretches with little traffic and the drive battery well charged, I put it in EV mode and select regen strength B0 to mostly coast and thus boost my MPG figure.
On the freeway, it’s okay in D (Drive) mode to use Charge or Save or “none” mode, that is, I don’t get the burning rubber smell in any mode, not even with 4WD Lock on. But if I did get the smell, maybe this might happen in a hot climate, I would first try keeping it out of Charge mode and if the smell persisted then keep it out of 4WD Lock.
Usually when on the freeway I put it in Charge mode when going either uphill or downhill and Save mode on level stretches, unless my battery is over 80% of full charge in which case I choose “none” mode and let the battery drain to about 60% to pick up some MPG.
The only time I use B5 is below 40 mph, in either Save or Charge mode, when I’m alone in the car, to build up battery charge (but, shifting to “none” mode at stoplights and stop signs, to cause the gasoline engine to shut off and thus save gasoline). B5 makes the ride too jerky to be acceptable when I have passengers, so with passengers I just keep it in D and Charge mode (“none” mode when stopped) unless the battery is over 80% full in which case Save unless absolutely full in which case “none” mode.
When I pick up and drop off passengers I do so in EV mode.
The only time I use B1, B3, or B4 is when coasting downhill in EV mode, with no other traffic, to apply braking action appropriate to the steepness of the downhill grade.
I use ECO mode only with zero other traffic in broad daylight, visibility unlimited, on wide open road, just so I don’t lose sudden acceleration capability, purely for safety reasons.
And there you have it: the driving regimen I have found gives me maximum gas mileage, with a minimum of settings-fiddling, and without smelling burning rubber or doing any other apparent damage to the car, during the past five years when I have used my PHEV as my fulltime Uber vehicle in Seattle.
