Front view of the all-new Toyota Prius (A Premium Touring Selection) Photo taken at Shimoguri Village

Toyota Prius 900km Review: “Surmounted its flaws, turning it into a car for long road trips” by Koichiro Imoto

In December 2015, Toyota Motor Corporation launched the 4th generation Prius (Prius Four hereafter), a hybrid in the C-segment. As I was able to test drive it covering a distance of 900km, I am posting a review about it.

Powered by a 1.8L inline-four Miller cycle engine, the Prius Four is already an improved version of the 3rd gen Prius. Furthermore, it has been completely revamped and incorporated with Toyota’s state-of-the-art technology. I test drove the A Premium Touring Selection, a luxury grade that costs 3.558 million yen because it has been outfitted with a car navigation system.

â—† Fully remodeled, it brings two generations worth of performance

The test driving route is as follows: departure from Tokyo, heading towards Aichi to Toyokawa via Tokaido. From there, I will pass the Japan National Route 151, and travel to the unexplored region of Toyamago in Minamishinano via the Japan National Route 473. The route back to Tokyo will be on Koshu Kaido from Lake Suwa. The Nagano area, with its continuous hairpin turns, is a pretty tough route for a conventional Toyota vehicle powered by a two-motor hybrid.

The Prius Four didn’t equal the standard of a non-premium touring car, but it delivered excellent performance, which I think is equivalent to two generations worth of updates from the third generation Prius.

The hybrid powertrain received the most remarkable update. The fuel efficiency that reaches up to 40.8km/l when traveling in JC08 mode is the highlight of the Prius Four. In addition to that, the hybrid system’s total power control for the engine and the motors were further improved, evolving into something different from the existing Toyota models.

To date, the ride performance of Toyota hybrid cars on hairpin turns like on Nagano’s narrow mountain roads is marginal at best. The correlation between the throttle valve in response to the amount of depression and the generated power is unclear. Hence, it frequently loses momentum when climbing steep slopes. Conversely, when the power generated is too much, the drive performance becomes stressful.

Incredibly, the Prius Four no longer has that issue because the throttle responds accordingly to the driver input, delivering the power anticipated by the driver. Furthermore, the previous model’s rough feel when the engine is revving to deliver power has been completely changed, making it quite comfortable. The coordinated control of internal combustion engine and electric motors, two power sources that have completely different characteristics, is very difficult. It felt that Toyota has been able to grasp the lessons they have learned over the past 20 years since the development of the first generation Prius. The absolute value of the output is not a big deal, but it would be interesting if they will produce a more powerful engine. However, that’s the role of other models, like the next-gen Lexus CT that has been based on the Prius Four.

â—† Extremely high-performance chassis adds a twist to the ride comfort

A long time ago, Toyamago Nagano flourished as a major collection center for the forest industry. However, the Japanese forest industry received a devastating blow in the 1980s caused by the yen appreciation after the signing of the Plaza Accord. This caused declining population in the area, and now, it has been completely deserted. Vast forests lined up, such as the Kyushu Mountains and the Kii Mountains, with mountains as high as 3,000m. It is geologically dynamic and is a magnificent place because of the presence of the Ryoke/Sanbagawa paired metamorphic belt, which joins Japan. Toyamago has a brine hot spring because 100 years ago, this land was submerged in sea water.

The road is composed of narrow, endless hairpin turns because this lightly-populated area has little transportation demand, as well as having a weak ground. The suspension system is an important factor to safely, speedily, and comfortably drive though this road. The chassis performance of the Prius Four, despite the harsh road environment, was adequately great.

The previous generation Prius becomes unsteady especially on sandy roads, its tires lose grip when driving on bad roads, and the understeering becomes sloppy when passing through high curvature corners.

In comparison to that, the Prius Four is able to much comfortably run through that same kind of road. It might be because of the lower center of gravity or the suspension’s additional capacity, but it sure gave an impression that the four wheels have a firm grip when cornering without the load being concentrated to the outer tires. The model I test drove was outfitted with 215/45R17 high-performance tires. Except for the tires, the Touring Selection and the normal model have the same spring rate and damping force of the shock absorber. Hence, I would guess that when cornering at low speeds, the normal model will have the same performance.

There are some things to be improved as well. The seat tuning and the steering tuning, which accurately relay the thrust force and the car’s lateral G to the body of the driver, have had no progress. Instead of delivering the car’s movements in real time, it felt like there’s a short pause before it is relayed. This might be because of the poor seat hold, as well as the soft suspension setting based on the evaluation of customers, or the soft rubber setting despite the suspension’s high roll stiffness.

Because it is a high-performance chassis, there won’t be any problems when riding on circuits and test courses, as well as when the route is all clear. However, when touring wherein the road environment changes all the time, this delay in information will lead to a bad ride performance. When the car movement and the bodily sensation is excellent, it is not tiring to drive even when driving on streets for the first time because the car will naturally go towards the direction you want to drive. Since they have improved the performance of the car, it would be better if this could be improved as well.

â—† Despite the troubles encountered, actual fuel mileage is 22.3km/liter

The fuel consumption when touring was good. The total distance traveled was 911.2km, while the fuel amount is 40.79 liters; hence, the average fuel consumption is 22.3km/liter when in full tank. The actual mileage was 6% less than what was displayed by the fuel consumption meter, which was 23.6km/liter.

I would like to point out how the actual fuel mileage is slightly lower than the suggested. While I was driving on Japan National Route 152 near Takato, the left front tire became flat. The fuel might have been wasted because after traveling tens of kilometers in this state, the running resistance had increased. Also, because it was late at night, I couldn’t call a road service, so I had to keep myself warm inside the car overnight. I estimate that the average fuel consumption displayed during the 11 hours that the car was not moving is approximately 2.8 liters against the distance traveled, so if we subtract that amount, the mileage is about 24km/liter.

Let’s look at the breakdown. According to a collected data, the round trip from Tokyo to the Miura Peninsula in Kanagawa, which was mainly via the expressway, has a distance of 147.8km with fuel mileage of 23.4km/liter (the fuel consumption meter displayed 25.1km/liter).

The 305.5km and 23.8km/liter mileage (the meter still displayed 25.6km/liter) was achieved by traveling on both expressways and regular streets from Setagaya to Numazu via Japan National Route 246. The 299.2km and 17.9km/liter mileage (18.6km/liter on the meter) was achieved by traveling the mountainous path of Minamishinano, traveling on local roads, spending overnight in the car in Chino, and going until Nirasaki, Yamanashi. Then the 158.5km and 32km/liter (33.4km/liter on the meter) was achieved by traveling from Japan National Route 20 towards the city until Katsushika, Tokyo.

You will be able to see it from the numbers, but at the last stretch of the touring, the air conditioning unit was on as a result of traveling on eco mode. Originally, I thought that the mileage will be 37.2km/liter in JC08 mode, but because I wasn’t patient enough to finish the test drive in eco mode as I did not like the comfort offered by a Toyota hybrid, my experience in driving it was shallow, and I couldn’t fully try it because of the construction being done downtown. The Prius Four is different from its predecessor. It was able to deliver that driving pleasure. Rather than focusing on improving the fuel efficiency, drive it as is and you are able to get a reasonably good fuel economy. Hence, it’s quite satisfactory.

I was impressed on the third stretch of the touring when I had to spend the night inside the car. Since I wasn’t expecting that I’ll be staying overnight inside the car because of a flat tire, I hadn’t prepared for the cold. There was no other choice but to use the fuel to keep myself warm inside the car. The engine will only start when the battery’s electric power becomes low and when the water temperature drops, so the fuel consumption during the overnight stay inside the car was less than three liters, which is less than half of what a normal car would consume. Furthermore, the seat heater was very nice. I put on a down jacket and slept, and it felt like I was undergoing a thermal healing. I was sound asleep until morning.

Ordinary cars can also have the same environment while the engine is on, but it is absurd to think of choosing a car with the assumption that you will be in a distress situation. But when an emergency occurs, there is a sense of security as it consumes less gasoline.

Ultimately, I have nothing to criticize about the Prius Four as an economical car for it has largely overcome the weak points of its predecessors, taking the Prius into a new stage. It reminds me of the first generation GM Saturn Coupe. The preferences regarding its mostly American looks seems to be divided, but it’s interesting to see what kind of changes it will make to the composition of the eco car market. This is because the drivability of Prius, which had been sidestepped until now, might encourage customers who are interested in long touring to have this product on their “to buy” list.

(Translated by Katherine N. Bantiles)