Good question! I have been wondering the same thing. Looking forward to some helpful input.
I only use it on steep hills or if traffic slows faster than I anticipated.
I have seen it turn on the engine before, but most of the time for me is doesn't. Using torque pro and an obd2 adapter, I can see it regens faster with L than coasting alone.L is engine braking, it's just throwing away energy. From what I can see using L gets less regn coming to a stop. If I use it when I could have lightly braked, I tend to get 80% or less return, compared to using the peddle getting 100%
Guess the truck decides based on your speed, every time I've used it, engine comes on. I find just coasting the truck slows down too much on the gentle hills I'm on most of the time, so I have to use the accelerator peddle to maintain speed.
I use L frequently. It is great for stop and go traffic where with very little practice you can one pedal drive and only use brake to come to complete stop. L will Regen to lower speed than each gear not in L. Helps in stop and go by much reducing hydraulic brake grab. Downside is Regen will rapidly fill HVB to 70% where Regen is greatly reduced and ice will start engine braking. Since battery will not accept the high Regen braking current safely. When in L if you want to get 100% braking you cannot touch pedal while brake gage is over about 60% or you will also activate hydraulic brake and drop return to 70-90% in a heart beat. Even then you will need a light touch above 15-20mph. Also do not overlook slippery mode particularly at highway speeds. It has the weakest Regen braking and will coast much further. You can save the conversion loss of momentum to stored current in battery. Search for member GPSMAN and slippery. He has run many tests in all gears and compares. I think he is 700+ miles per tank sometimes.
Additional thought. Normal mode with L is stronger Regen than econ mode with L and slippery mode with L is less regen than econ with L. I haven't ever tried sport mode at all, yet.
Good thought.. Texas here....I don't get into slippery that much.
Slippery can be used on wet and slippery surfaces but TRY IT ON REGULAR DRY. It feels like driving a regular automatic (coasts for ever with minimal Regen). It will allow driver to brake more aggressively Regen braking without engaging hydraulics. Without flooring go pedal but with reasonable acceleration I can regularly get 40+mpg without trying, just regular driving. I am NW of Austin, TX, Burnet - Marble Falls area. Again read gpsman posts concerning slippery. Have fun!
I don't see much difference with eco/L over normal/D. Usually get 46-51mpg either way. 36-40 highway.
