By the time I pulled into my garage, the dash showed me that I’d averaged 4.7 L/100 km (21.27 km/L), my all-time best on 110 roads.
BHPian supermax recently shared this with other enthusiasts:
I happened to do some hypermiling on a recent trip, and thought I’d share my experience.
My 2020 Skoda Octavia 1.0 TSI 115 returns about 15 km/litre on average in the city, and between 18 and 20 km/litre on the motorways, averaging 110 km/h. My family and I had traveled to Södertälje and Sundbyberg, near Stockholm in Sweden, to visit friends and celebrate Yugadi (Hindu New Year) at the Hindu temple there. Our journey back to Linköping was a 170 km drive from Södertälje, and we decided to do a non-stop journey, if my son dozed off, and that’s exactly what he did.
There was a light drizzle which turned into heavier rain, but I held a steady 100-110 km for the first 80 km of the trip. I was in the mood to see how efficient I could be, so decided to not engage cruise control at all. My friends in India may not think so, but my experience in driving in Sweden shows me that I get better fuel economy when I manage the speed myself, with a light foot, than with the cruise control on. The reason for this is mainly the rolling nature of the roads. When driving with a light foot, I don’t always hold the exact 110 km/h when going up an incline. I maintain the gas and only add slightly more, not minding if my speed drops from 110 to say 98-100.
Using the CC here would mean it aggressively accelerates to keep the speed up at 110, and this causes a lot of extra fuel consumption that the car cannot recover when the road flattens out. It also brakes slightly to prevent the speed from exceeding 110, when descending, and this is also something that I don’t do when I’m driving. I’m okay if the speed goes up a bit knowing that it’s not a significant increase (<10% over the speed limit) and the additional momentum helps the car to glide up part of the next rolling climb easily.
After the first 80 km, I saw that the car was averaging 5.0L/100 km (20 km/l) and that’s when I saw a tourist bus ahead of me doing a constant 103 km/h. I decided then to slot behind him for as long as our paths didn’t diverge. I now chose to engage the cruise control, as I didn’t want to be bothered with holding an exact 103 km/h speed or risk getting too close to the bus, or falling too much behind him. I maintained a gap of just over a 100 meters, rarely getting closer than that. If the gap grows more, the aero advantage steadily declines, but more importantly, cars that might overtake me might choose to slot in between the bus and me, if there was somebody behind them in a bigger hurry.
Since the gap ahead of me was just right, those who overtook me also ended up passing the bus in the same move, before switching back to our lane. Hogging the overtaking lane is an offense that’s punishable by a steep fine, so most people use the left lane only to pass, and then switch back as soon as it is safe to do so, i.e. ensuring adequate separation to the newly passed vehicle. A couple of times, the bus ahead of me had to make his own overtakes on cars with coupled trailers, which can’t exceed 80 km/h on the motorways. When this happened, I generally coordinated my own pass so both the bus and I moved to the left lane too in lock-step, but on a couple of occasions, I was not able to move as there were cars approaching me from behind on the left lane, so I let them pass me, but planned my lane changes to get behind the bus again. In this way, I did a total of 86 km behind the bus, before I had to take the exit for my home city! By the time I pulled into my garage, the dash showed me that I’d averaged 4.7 L/100 km (21.27 km/L), my all-time best on 110 roads.
Would I consider doing it again? Absolutely, if it’s a bus that’s holding a steady 100+ km/h, but not trucks which aren’t allowed to exceed 90 km/h. The difference between 90 km/h and 100 km/h might not seem much, but in the case of the former, it would mean way many more overtakes, and I really don’t like people closing in on me, on the right lane, with a speed differential in excess of 20 km before they pass me. For this reason, buses are good, trucks, not so much. I have chosen to crawl behind a truck in extremely torrential rainfall once, but that was not for fuel economy as it was for plain survival; driving a safe distance behind the truck, but not passing it meant that I only needed to be able to see his taillights, instead of being able to see all of the road in the extremely heavy downpour.
I realized also on this trip that adaptive cruise control makes it really easy to hypermile behind buses. With my manual cruise control, I still had to click it up and down a few notches, in response to the bus ahead of me, to keep the separation a constant distance, something that an ACC would have done for me all by itself.
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