The hot weather has really helped improve my fuel consumption. Despite using the A/C regularly to cope with the extraordinary heat, I was getting very good FC numbers. At 482.8km my FC was 3.7l/100km (3.9 corrected) and the Distance to Empty (DTE) showed 442km. That’s a total of 925km according to the very conservative DTE reading.
If I’d maintained that 3.7 on the HSI (or 3.9 corrected) for the 925km, I would have used 36 litres from a 45 litre tank.
If I then drove using every last drop, those 9 litres would have taken me another 230km for a total of 1155km or 717 miles.
A 700 mile tank was within reach as long as a long line of ifs held true. So then what happened?
I’ll be taking a few more trips to Newcastle over the new few months. My father is recovering well and we’re helping him with a few jobs around the house. So there’s a few chances to baseline the fuel consumption under fairly arduous conditions. Parameters:
Tyres at 45psi
Lower grill fully blocked
Full tank of Caltex 91 RON (ethanol free)
Temperature 10 – 20°c
The run from Canberra to Northern Sydney was at night from just after 21:00. Not much traffic and sticking to the limit, even up hills. The mythical Super Highway Mode still eludes me. Rather than cut through Bankstown, Rhodes and Ryde, which is nice but hilly, I took the M7 and M2. I chose that route as I assumed that the roadwork I had encountered on the M2 a few weeks previously would either be finishing or would at the very least be no worse. Boy was I wrong. The entire stretch of the M2 I used was a 40km/h zone (I remembered it as a 60km/h zone!) adding about 30 minutes to an already long journey. Arriving at midnight is not too bad. Arriving after 00:30 seems silly.
Early start to Newcastle on the F3 carrying a niece and nephew as cargo. The F3 is a bit busy and a bit hilly for cruise control. Pleasant drive interrupted by a wanker driving a black Volvo XC90 who overtook in the left hand lane (contravening Rule 141 and common sense) and then cut me off received a good toot from my horn and some choice words from the grown ups. Language warning belatedly given to the young children in the back seats. Obligatory toilet stop at Ourimbah for the youngsters didn’t delay things too much, I thought.
After a highly productive day we returned in 3 cars: Sister and brother-in-law ahead, us in the middle and Dad behind. We managed to maintain this order for the entire journey and for some parts had no other vehicles in between. I thought that I should keep an eye on Dad so I kept a reasonable distance ahead of him. This meant charging up the many steep hills on the F3 at nearly full power. Not great for fuel consumption. Here’s the funny thing; our formation flying was a complete fluke. Dad had left before us but had discovered a new dead end. The two other cars left together, but the superior torque of the Citroën turbo diesel allowed it to overtake on Carnley Avenue. Dad appeared in my rear vision mirror and stayed there for most of the journey. Arrived in Northern Sydney within 2 minutes of each other.
Roundabout way of saying that we travelled 854.6km (about 10km past the DTE=0km mark) using 38.22l of petrol at 4.47l/100km. Considering the flogging I gave the car, it was about 0.5l/100km better than I would have expected a few months ago. The return journey to Canberra was 284.0km at 4.6l/100km (4.2 on the HSI) at an average speed of 92km/h.
So, did the grill blocking help? It’s possible that it helped the aerodynamics at high speed. Just wait until the next tank fill; I’m expecting low 4’s. That’s almost certainly down to the rising temperatures. And the grill block.
Fuel consumption settled on 4.56L/100 km. Quite pleasing given the circumstances.
Pros: warmer weather, grill blocking (for the last 150 km) and generally smooth driving helped provide a reasonable result.
Cons: mornings are still very cold and my wife drove about a ¼ of the distance. Her approach to acceleration is fairly brutal. This is not always a bad thing, as it will charge the HV battery, which in turn can be used to help drive the vehicle. However, her braking style doesn’t take advantage of regenerative braking.
Curiously, the HSI displayed 4.1l/100 km, which is wildly optimistic. The HSI error seems to have increased from 6.5% to 11.5%, but that might just be an anomaly.
Weirder is the Garmin ecorouteHD, which has gone from being a highly accurate FC meter to become even more Pollyanna. It regularly shows trip FC of mid 3 litres or even in the 2’s when the true figure is about 25% more. Only started happening after upgrading the Garmin firmware…
Last couple of fill-ups have been rather disappointing. After a spectacular 4.5l/100km performance, I’m back down to 4.8-4.9. To make matters worse, on Friday night (#19) I had to pay 155.9¢ for RON 91, which was about 10¢ more per litre than everywhere else. Not a fun drive with the wind, debris on the road and veering from one edge of the lane to another. I had almost 8 litres left, so I could have driven into Sydney and found much cheaper petrol, but I played it very safe. The Prius has a 45 litre fuel tank, but it is monitored by a very conservative Distance to Empty (DTE) readout. I once drove 35km after the DTE read 0km and I still had more then 5L left.
(My previous cars had very accurate DTE; I once put 54.75L into a 55L tank when the DTE read 3km!)
I passed through Bankstown at after 22:00 and was briefly caught between jubilant Bulldogs supporters waving flags out their windows and hooning about a bit. Far less threatening than the mayhem I had driven through to get to that point.
Canberra, Sydney, Newcastle return. Very windy conditions. Difficult to keep a straight line. A tailwind would have been nice!
Very windy conditions. Car tossed about and difficult to maintain steady speed.
Mostly a Canberra to Sydney return trip with an extra lap of Sydney driving in heavy traffic. Generally warm weather, but a very strong cross wind.Finally cracked 4.5l/100km on a tank.
Tank #20 was from Sutton Forest, Sydney, Newcastle, Sydney and back to Canberra. The F3 Sydney to Newcastle is very mountainous. IMO there are more steep hills on the F3 than the Hume/Federal Highways from Sydney to Canberra, despite being 1/3 of the distance. You ultimately do more climbing to reach Canberra at 600m ASL, but it is more gradual and only 3-4 hills require digging deep. On the F3 abundant flat sections are punctuated by steep hills; especially around the Hawkesbury River. I was braking lightly and still accelerating on downhill sections; the charge I gained was quickly used climbing back up again. As mentioned in my Fuelly.com comments, it was very windy from Friday until late Sunday. It was hard to keep the car within the lane and this no doubt affected fuel consumption. And the fact that I was in somewhat of a hurry… maybe that had something to do with it.
The Prius major service occurs at 80,000km. That seems a bit early compared to 90-120,000km major service on my previous cars. One big difference is that I didn’t have to replace the water pump and timing belt. The Prius has a timing chain and there’s no set interval to replace it, just like old V8s.
Instead the parts to be replaced were fuel filter, including in-tank fuel filter, oil and filter and brake fluid. I’m slightly concerned that they used 10W-30 instead of 0W-20 oil considering how cold it has been and will continue to be. But at least the car got a proper service and now I’m starting to see fuel consumption in the threes.
Drove from home to Civic tonight on a warm engine. At the intersection of Northbourne and Antill Streets the HSI read 9.1km 2.8l/100km average speed 50km/h. That’s 100.9mpg(UK), 84.4mpg(US) and 35.7km/l. I reached Civic at 2.9l/100km and the round trip settled at 3.4l/100km. That is 1l/100km better than several comparable trips I’ve taken in a warmed car on a Friday night.
It’s no surprise that a major service should restore some vigour to the car. But since the change (on a sample size n=1) is so great… how was the car treated before I got it?!?