Prius tank-by-tank and year-on-year

My fuel consumption is much better than last year.  My first few fuel ups from January to March 2012 were:

  1. 5.3l/100km (estimated)
  2. 5.4
  3. 4.9
  4. 4.9
  5. 5.3
  6. 4.8

By comparison, this year to March my numbers are:

  1. 4.1
  2. 4.0
  3. 4.2

Yes, 1 fillup per month in 2013.

In 2012 from the end of January to mid-March we travelled 3661.9 km using 185.79 litres at 5.07 l/100km.  In 2013 from mid-January to early March we travelled 3001.9 km using 123.25 litres at 4.10 l/100km.  That’s like improving from 46.4 to 57.4 mpg (US), 55.7 to 68.9 mpg (Imp) or 21.2 to 24.4 km/l.

Why the big difference?

There’s a number of things that have changed from when I first bought the car:

  1. Driving technique.  I am much more conscious of how to get the best from the car, specifically Pulse and Glide, Driving without Brakes (not literally) and maximising regenerative braking.  Super Highway Mode is still a bit elusive for me, but I achieved a very high level of right-foot mastery.*
  2. Engine heater and grill block.  Together these get the engine up to temperature and keep it there.  The Prius’ startup modes respond to coolant temperature; the hotter it is the more EV and power you have access to.
  3. Tyres.  I had 3 Ovation ecovision VI-682 and a slowly-leaking Bridgestone B205 at 34psi.  Now I have 2 Bridgestone ecopia PZ-X and 2 Ovations at 47 psi front and 45 psi rear.   I know that the Ovations were an end-of-lease quick-fix to having 3 bald tyres, but why doesn’t Toyota fit low rolling resistance tyres from the factory?
  4. I replaced a dead 12 volt battery in late March 2012.  This could have caused poor fuel economy by requiring more from the HV battery and therefore engine to recharge the 12 v.
  5. No cruise control on the highway.  CC doesn’t know when the accelerate except to keep the speed constant.  This includes a very handy feature of using regenerative braking on downhills.  But it is nowhere near as good as a well-placed right-foot.
  6. I ignore Distance to Empty = 0 km.  You have about 9 litres of fuel left when that warning
  7. Major Service in July.  If anything has been lurking, it will probably be found and fixed.  Improvement in fuel consumption should be obvious… unless everything was perfect beforehand.
  8. LED lights, shark fin antenna and subtle aero tweaks.  These are minor changes.  Indeed some in the eco-modder community wonder if the OEM antenna is even long enough to be affected by the air streaming over the car.  But since they make the car pretty and don’t take away efficiency, they can stay.
  9. I use 91 RON instead of the “recommended” 95 RON.  The user manual says that fuel of 90 RON or higher should be used.  However, the fuel flap “recommends” 95 RON.  Research from PriusChatters shows that 87 AKI (91 RON) produces better fuel economy than 91 AKI (95 RON) in the Gen III at least.  Particularly if you very rarely rev the engine beyond the Eco zone, the extra energy in 95 RON is not put to any use.
  10. It is dryer and probably warmer this year.  Temperature has a big effect on fuel consumption and the hot weather has helped.

The real test will be to see how much of this I can maintain during a Canberra winter.  I suspect that I won’t be much better if at all because I had already adopted a lot of fuel-saving measure before last winter.

* I drove my Citroën C5 for the first time in a year yesterday.  The steering is very heavy (but good heavy), the throttle is so quick to respond compared to ECO mode on the Prius and the brakes are very strong; a Citroën trait.  And I can’t believe how low I could have my seat and how high I could have the wheel.  I only used the wipers instead of the indicators once, but I kept trying to engage the parking brake with my foot!

 

1132.5km on 45.17L – But is it enough?

1132.5km at 44km/h.  A shame that the 3.7 l/100km figure is so unreliable.
1132.5km at 44km/h. A shame that the 3.7 l/100km figure is so unreliable.

I should be very happy.

  • I’ve just registered my best fuel consumption result of 3.99L/100km.  That’s 70.8 mpg Imp, 58.9 mpg US and 25.06 km/L.
  • First dot lasted 177 km
  • Fuel warning beep at 903.3 km
  • DTE = 0 at c. 960 km, driving another 170 km.
  • My last 553.7 km was at 3.5 L/100km (3.7 corrected 63.5 mpg US) and 45 km/h

I’m sad because I was aiming to drive 700 miles (1126.5 km) on a single 45 L tank and I’m not sure if I made it within any margin of error.

Continue reading “1132.5km on 45.17L – But is it enough?”