I just spent most of the past week driving 1500+ miles in a 2017 Mirage CVT. I did a little hypermiling. I did a lot of back roads driving. I did a little highway/interstate driving (tried to avoid that), and a little hilly driving, mostly with "pushy" traffic. No actual mountain driving. Learned a few things.
I'm sure those who have spent even more time with the CVT, especially if they're the technical sort, have learned even more than I have. But, I'm going to try to share a few of the things I observed before I forget them.
The first thing I did in the car was an hour-long hypermiling trip. Wasn't planned, it just happened that when I was driving it home for an hour, there wasn't much traffic and I could pull it off. Didn't go over about 52 mph. Got in some great coasts, and some pulse and glide. Was able to accelerate super-gently most of the time. And got home with over 60 mpg on the display. Cool! From that trip, I felt like the CVT was pretty cool. Seemed to always be in the right gear for what I was trying to do, and was fairly smooth most of the time.
Then I read about how it works. Drove it around town a little bit for a couple days. And put some wider non-eco tires (185/55-15 Toyo T1-R) on it. Gas mileage TANKED immediately. But, when I got around to checking tire pressures, they were at like 31. I upped them to 45, and mileage improved quite a bit. Still getting pretty easy 40+ driving around town casually. Nice.
Then I started my road trip. Florida to Kansas, mostly back roads, no interstate. I had plenty of time, but didn't want to get behind should any problems develop, and didn't want to be holding up traffic, and I just enjoy driving at a certain pace on certain kinds of roads. So, after the first tank, I stepped up the speed.
The first tank I had 50-52 mpg going on the display. Worked with some rush-hour traffic to keep speeds down and generate some stealthy coasting. It was working well. But, the last half-hour was on a 2-lane quiet and dark road... and, well... I just got bored and started driving faster. 65 mph dragged that 50 mpg down to around 47 and I was okay with that, thinking that I might be able to hold onto averages in the 40-45 range for the whole trip. But, my fill-up showed differently. Not sure why. Every other fill-up was accurate to within a percent or so of the display. But, the first one was WAY off, showing actual MPG much less. I'm writing it off to "fill shut-off error" either on the first or second fill-up, maybe both.
The rest of the trip netted around 37-38 mpg average. And that included a LOT of 65 mph driving. Some 70-72. Some 55-60. And a little bit of 75-80. Not the MPG that I wanted. But, really... for the way I was driving, it was respectable. There was also quite a bit of rain for the first 1/3 of the trip, and a BUNCH of cross-wind and head-wind action that didn't help things at all.
On to the quirks!
First, if you know the mechanics of this thing, you'll know two things. One is that it has a two-speed "gearbox" along with the actual CVT belt-driven system. The other is that it has "idle neutral logic" that puts the car in neutral when you stop so that the engine can idle with less fuel while you're stopped. Both of these things are not too noticeable if you drive like a normal person, and you're used to driving an automatic transmission that shifts.
The high-low thing you won't quite feel much if you accelerate very lightly (like my first trip). It will drop into high almost immediately, and you'll slowly accelerate through the CVT from there. But, if you accelerate more briskly, it will hold onto "low" for a lot longer, and at some point, it makes a big jump where it's shifting to "high", and the CVT is having to jump way down in ratio to match it. Both of those things happen at the same time, and it's not always smooth. You get used to it. You can even learn to work with it, just like you would with a regular automatic trans. You just have to know that the trans is going to hold that last "shift" as long as you're accelerating. As soon as you back off and go into cruise mode, it will shift into high gear. The CVT does the same thing it's just shifting from low to high, AND adjusting the CVT to a high ratio.
The idle neutral thing I don't think most people would notice because they tend to brake harder than they need to and stop harshly. If you do that, you are fully STOPPED when it shifts to neutral and you don't feel it. But, if you're a light-braker... you're making a slow, super-smooth stop... and right before you're stopped, it reaches some arbitrary threshold where it thinks you're stopped and drops it to neutral with a little clunk... and it messes up the smoothness of your braking at the same time. I found it pretty annoying because I'm usually a gentle stopper. I try to be in "limo driver" mode. Nobody needs to feel that I'm braking. I don't want to bounce the car around.
The idle neutral thing can also sometimes be felt when taking off from a stop. Again, if you're SMOOTH, it's fine. Just remember that the first thing that happens when you take your foot off the brake is that the trans has to shift from neutral back into Drive. That takes a half-second or so. If you ease off of the brake and onto the gas, it happens seamlessly and smoothly. But, if you're in too big of a hurry, and just instantly come off the brake and jab the gas, you'll FEEL that shift out of neutral. It can be HARSH, and I'm sure that doing that is not healthy for the transmission. I'd recommend not doing that. "Doctor, it hurts when I do this." "Don't do that." Mechanical empathy. If it feels like it could be hurting the car, it probably is. Don't do it. It's particularly bad if you're like almost stopped, and the transmission JUST shifted to neutral and you jab the throttle at the same time. Even worse if one wheel is on a slick surface when you do that... then traction control kicks in at the same time and it gets all kinds of sloppy.
But, the WEIRDEST thing I noticed, and this happened more than a few times in two different circumstances. If you're accelerating, say up to a significant speed. 60-65 or so. If you happen to be going uphill, or you happen to be fighting a headwind... as you're accelerating, you might never reach that point where you "lift" off of the throttle to get into "cruise mode" (see above). Because you're fighting a hill or a headwind, you keep your foot in it, and the last part of your acceleration to your target speed might be a little lazy... and you just settle into your speed without that traditional "I'm done accelerating now" throttle lift. If you happen to find yourself in that situation, you might notice that the engine is revving something like 4k rpm. You're going 60-65 mph, and the engine is revving like mad. The solution? Lift off the throttle. Just a little bit. Force that "shift" into cruise mode. RPM will instantly drop to 2500, and then when you get back into the throttle, it will adjust to probably somewhere between 2500 and 3200 depending on how much of a hill or headwind you're still fighting. I found myself driving for a couple minutes fighting a headwind at one point just like that before I realized it. Engine was just humming away, and I wasn't paying attention. Watch out for that. Be in tune with where the RPM's are and what the engine sounds like. Even though it's an "automatic transmission", you still sometimes need to be aware of what it's doing and "help" it by giving it the input that it needs.
Some people say the transmission hunts a lot. Well, yes and no. If you're just cruising on fairly level ground, it pretty much doesn't. If you're going up and down hills, or constantly adjusting your speed, then it will. What it does is RESPOND, which is a good thing. The engine doesn't make a lot of torque at low RPM, and it knows it. So, when you put the "demand" pedal down, it knows that the only way to give you the acceleration that you just requested is to rev the engine up higher. So, it does. It's not a bug, it's a feature! You just need to learn to work with it.
I did find that using the Sport mode made it a lot easier to accelerate briskly from a stop without having to give it a bunch of throttle. But, I also found that 90% of the time just giving it a little more throttle and staying in D was adequate.
Sport mode was fun for getting better throttle control to modulate speed going into curves sometimes. Where you don't really want to brake, but you want to slow down a little bit, and you want finer control of the throttle to accelerate out of it at just the right time. It worked well for that. Staying in D... the throttle was less controlled. Bouncing from "cruise mode" to "acceleration mode". Sport mode sort of keeps it more in the acceleration mode. (so you don't want to just drive around in Sport)
Sport mode was also VERY useful for keeping up with traffic on a fast-moving hilly road! Trying to do that in D was frustrating and definitely very "surgy". Sport mode gave the responsiveness needed to get the heck up the hill when you needed to, plus better engine braking on the other side.
I never really used the "Low" mode on the trans. I guess that might be useful for a long downhill stretch, particularly a slow-speed one. I never got into a situation where I needed more of a "downshift" than just dropping into Sport mode.
I guess my best advice to anyone who's having trouble learning to deal with the Mirage CVT and finds it hunting too much would be two-fold. First, try to have a more steady throttle foot. Establish a speed and keep it. Make more subtle adjustments and the transmission keeps up and responds quite well. But, if that's not working for you either due to your habits, or the conditions you're driving in... don't be afraid to use Sport mode. Try to keep it in D as much as possible for low-RPM cruising, it will get you better fuel economy. But, if you're trying to accelerate, trying to keep up with some traffic that's not moving at a steady pace, trying to get the heck up this hill... try slapping it over into sport mode. See if it doesn't feel a little better.
In D, it wants to "upshift" into the highest gear ratio that it can if it senses that you're not accelerating. It will adjust from there, but it tries to response QUICKLY to your requests, and sometimes that can feel weird and/or annoying. If you're in Sport, it keeps you in the power band so that it doesn't have to make those BIG gear ratio adjustments, thus is feels more consistent... but, also more responsive because you're already in the power band.
Try to work with the transmission instead of fighting it. It really is a bit of a technical marvel. You just have to figure out how it wants to be driven. It CAN be clunky and bumpy and awkward. You can learn to anticipate and drive around most of that, or just drive a little differently to not cause those problems. It can also be somewhat engaging and fun and satisfying to drive once you start figuring it out.
Anyhow, those are some of my observations. Feel free to chime in with your own. I know there are people who have spent a LOT more time with the silly things than I have.