I would appreciate POV from owners of T8 hybrids as to when and why you use the "D" vs "B" gear.

I drove two different Lexus Hybrid SUVs for nearly 11 years and am comfortable how the Lexus RX hybrid implementation works, as well as what I could and could not do to improve my performance vs MPG and vice-versa. This week I placed a new 2020 XC60 T8 Hybrid on order. I have read the XC60 T8 owner's manual front-to-back, and searched the web-o-sphere, but it's still not clear to me what's really going on with some of Volvo's hybrid implementation under the covers, so I'd appreciate clarification from others that drive any Volvo T8 -- which I suspect are all similar from model-to-model to what I'll have in my XC60, except of course the varying performance given physical vehicle differences.

What I know:

• Lexus hybrids do hybrid battery regeneration automatically during most of the braking process.
• Lexus hybrids also always automatically regen as the ICE brakes against itself with driving -- not requiring any further owner action, e.g. going downhill or as you take your foot off the brake when the ICE helps slow you down. This works really well, as e.g. when I drove my old RX450h from SoCal to Vegas which is 300 miles one-way on mostly freeway -- and 2K feet higher on a fairly gradual incline from where I live -- with similar traffic and speed, for each of those trips I consistently got 3-4 less MPG on the way "uphill" to Vegas, than on my way "downhill" home when my MPG soared in comparison.

What I'm puzzled with:

• From only reading the XC60 T8 manual, I'm left with the impression that the Volvo Hybrid implementation only performs the automatic braking version of regeneration when you are in "D" gear. If you also want the Volvo Hybrid to perform regeneration when the ICE is braking against itself in normal driving, you have to run in "B" gear.
  • Of great interest to me is neither of my former Lexus hybrids Had a "B" gear to select from.
  • So, why has Volvo made the choice to separate the two forms of regeneration and create a unique "B" gear?
  • Is it maybe just a performance difference between the two -- with "D" on average being the best performing with some MPG impact, whereas "B" does not perform as well ,but in theory may provide better MPG? If so, what have you found?
• When I posed this to my Volvo salesperson (who was fabulous, but definitely has not lived with a Hybrid or EV as I consistently have for 14 years), she demonstrated PURE mode (which is like an EV with a really small battery -- I get it), and a dash touchscreen option to force the T8 to recharge it's hybrid battery using the ICE, but neither of those functions answered my question. So, I said to her, "Why wouldn't I just want to run in "B" gear all the time?" Her response was "Sure, you could." But she couldn't tell me "why" and explain the real differences between "D" & "B" gear -- and neither does the XC60 T8 Owner's Manual from what I found in my marathon reading.

Thanks to all for your assist in my understanding while I wait for a ship date of my new XC60 T8!!! I’ll keep up my pursuit to understand this elsewhere in the meantime.

 

I’ve spent several more hours trying to research this, and believe I have at least come up with a supposition what may be going on with Volvo’s Hybrid based on what appears later year Prius are doing with their “B” gear (which wasn’t available in old Prius or either of my former Lexus RXh.)

For simplicity and to reduce combinations, let’s say I stay in XC60 T8 Hybrid mode:
If anyone can confirm my supposition how Volvo Hybrid’s work between D & B-gear, or correct me if my guess is wrong, that would be great. Otherwise, my investigation is over until I receive my new XC60 T8 in a few months and can try it for myself.

 

Have your thoughts changed on this subject after owning and driving for a year? Thanks. I just bought a 2021 XC60 recharge and have similar questions.

 

First, congrats on your new 2021! That's exciting!

Yes, my POV I was I was trying to develop in this thread prior to purchase, has changed substantially since I took delivery in late December 2020 of my XC60 T8.

I learned to move the shifter one more notch every time I get in to my T8, and drive exclusively in "B" Mode unless I forget to by accident -- the last time when I was just pulling into my garage after a hand wash. [img]images/smilies/wink.gif[/img] I have found zero reason to not use "B" for my purpose and see only possible upside for the way I drive and use my T8. In fact, using my iOS Roadtrip App where I've manually tracked gas mileage since taking delivery 8 months ago, I'm showing my XC60 T8 lifetime MPG as 70.24 right now.

IIRC, there is at least one poster on these boards who highly disagrees with my POV, says they never use "B" and have observed no or minimal benefit. OTOH, at least 2 others have corresponded with me via PM saying they use "B" as their primary gear after reading some of my other posts in the months since I took delivery. I believe your mileage (literally) will vary based on where and how you drive. T8 regen design is minimal compared to what I knew of my former EV. Over-simplifying here on purpose: T8 "B-gear" just gives that T8 regen logic a bit of a boost in some situations to improve regen when it can. The area where I live is rather hilly; While I drive around town for most of my trips, there is a lot of 45-55 MPH on primary roads; I don't drive a lot of higher highway speed and long trips especially in these COVID times, but when I do, I love the long on-ramps here in CA to get quickly up to speed ; I also tend to drive my T8 more like I did my former Tesla with one foot on the accelerator most of the time; and while I don't believe I drive like some old grandpa that shouldn't be on the road, I am not someone who has to be the first one off when the light turns green to get far ahead of the pack, and I try to use physical brakes as little as possible to anticipate my stops and slow as much as possible just releasing the accelerator in advance where I can.

Everyone's driving pattern and situation will vary impacting how the benefit of "B-gear" shows to them up or not. For me though with my now practical experience, for anyone who asks, I suggest running in "B-gear" as their default. There is only probable upside in doing so.

Good luck with your new ride. ENJOY!

 

Thanks for the info

we will use the car in Pure mode most all the time in town (which is most of our driving).
we tend to take long road trips (5-10hour drives) and on those trips I guess I won’t see much improvement in hybrid mode unless it is hilly terrain,
I do think B mode though will be the way to go.
first ‘long’ ride is tomorrow About three hours. Some of which is in traffic (Boston area)

thanks again

 

Having had an XC90 for 10 years I have concluded that the optimum efficiency is D Drive but use the B drive like a lower gear ie going downhill to slow down, on ice/snow, coming up to intersections, traffic lights, stop signs. This requires anticipation and spatial awareness because B is only a slow brake, and the willingness to flip between D and B with a flick of the hand. It does produce the most miles on electric.

 

I believe the D mode allows the car to coast better akin to neutral when the engine is not required such as gradual downhill and therefore saves fuel. The B mode is more to save on the breaking side esp for steeper descents and will make more of the regenerative breaking. I haven’t driven mine enough to really tell especially in mountainous terrain but I’m thinking outside this type of driving they make relatively little difference.

 

I am picking up my first Volvo (XC90 T8) this Saturday from Overseas Delivery Program and cannot find anyone who can advise me on the B gear. I will be driving about 87 highway miles each day (from one location to another and back) and the electric range will obviously not get me there in Pure mode so Hybrid is my choice. Can I drive the B gear on the flat highway at 75 mph or will this harm the engine/batteries? From reading your posts, the B gear is only advantageous if braking frequently and in hill driving...yes?

 

Any additional thoughts on this topic after driving for some time?

I would like to use the B gear as my primary driving mode. Am just wondering the effect it has on (if any) on gas mileage, additional wear on components, etc. Incase you need to know, I live in an area that is mostly flat with about 70% highway driving.

Thanks!

 

HAD, I've been driving my T8 (which I LOVE) since October and already have almost 23 K miles on her. I have not noticed any gas mileage difference between using the D or B gear but then I'm driving primarily flat open highway. What has been the most positive impact is driving her significantly slower than the 75 mph speed limit and eliminating fast starts/stops. I took her to Austin dealership for her 20 K checkup and the head service guy was amazing. He listened to my litany of questions and then patiently answered them all...something the Lubbock folk could/would never do.
Regarding the D versus B gear question, he said it wouldn't have any noticeable effect if I'm driving on flat roads; said the B is truly meant for hilly, mountainous driving where the engine itself helps slows the car down (like the old second and third gears?). He indicated anytime the brake is pressed, either in D or B, the batteries recharge.
Also asked him about the Off-Road drive mode. I was putting mine in Off-Road to go down a mile long caleche road that, though lots of small rocks, was fairly level. He said that wasn't necessary...he indicated that when he was at the Gothenburg factory, they test drove some truly off-road trails...where only three wheels are touching or the car has two wheels on the ground and the other two on a rock wall. Said my dirt road wouldn't qualify as off-road
He did say using top premium gas (minimum of 91) is important for the engine and not to go lower.
I hope this helps. Enjoy the road!

 

What a detailed and thoughtful response. This is incredibly helpful, thank you!

Sending good vibes your way from South FL! I just learned that Volvo comes from the Latin for "I roll", so I say to you: roll on and prosper!

 

I have my xc90 twin engine T8 since 2019. We noticed an interesting use of the B gear, which we kind of use as one used switching to a lower gear on manual gear driven gasoline only cars: to use the engine compression to brake and not overheat the brakes. So if we go downhill, we switch to B. Now note, being in B is kind of reducing the current gear by one notch: so if you already drive slow and are in D, switching to B makes you go slower. This means: when you use this to go downhill, reduce the speed to a good speed going downhill and then switch to B. If you brake strongly (i.e. to make a sharp turn), the gearbox will automatically switch to lower gears, and coming out of the turn, you might notice you go really slow now - because I think in B the gearbox does not switch to higher gears. If you are in B and you switch B once more, the gasoline engine will come on and you start braking additionally on the engine compression (this was a new behavior we noticed after a late 2019 software update!) - as with older gasoline only cars, switching to lower gears to save the brakes. We also noted that going downhill in B seems to charge the battery faster then being in D (and using the brakes more frequently). So we adopted a pattern to switch to B whenever we anticipate that we have to brake: going downhill and sometimes as we see congestion in front. We never made representative measurements of fuel use and battery loading. But coasting on flat roads feels better in D.

 

Thanks Toni! Really appreciate your response.

 

I have a related question. I have a nXC60 T8 2022 and I am curious about the most efficient drive settings for long trips. Currently (for no actual reason) I start in Hybrid Auto and switch to Hybrid Hold when the battery drops to about half capacity and drive the remainder of the trip in Hold

But I don't know:
1) What's the difference between 'Auto' and 'Hold'. and what's the difference between Auto at zero battery range and Hold.
2) Should I let the car start out in Pure on a long trip.

Unrelated but any suggestions to what to do on a month-long trip with undetermined access to overnight charging? I am assuming that roadside 'Fast Charging' is not available as the connection is a J1772 and the internal inverter is only about 3.3 kw. Please correct me if I'm wrong.

Thanks