-   Success Stories (
-   -   The 66.6 mpg challenge (

groar 12-06-2008 05:25 PM

The 66.6 mpg challenge

Before the end of the year, we will have to travel several times, each time for 2 to 4 hours.

I'm preparing myself to obey ecomodder's commandment #50 :

50) Make fuel economy a game/challenge
Even if the scenic consumes a little more than the megane between my hands, it's more comfortable, has more room and has a onboard computer with instantaneous and average consumption which will be an advantage on these unknown routes. With the scenic I had several daily commutes at 57 mpg during last weeks and could have some trips at 67 mpg when the engine was hot.

In ideal conditions I can reach 100 mpg at 43.5 mph and 75 mpg at 50 mph. But these figures are achieved only when I'm alone and on my daily commutes. These travels will be done with 2 adults, 1 baby and some stuff for 1 to 5 days.

I don't think I can reach 79.9 mpg or 68.54 mpg because it's cold (first sub 0°C nights), windy (up to 50 mph this night...) and rainy nowadays, but to do my best I have to attempt an unreachable goal and 66.6 mpg (3.53 L/100) looks so coool :cool: (no offense here).

I will not put the wiper cover back or try to build rear wheel skirt quickly (it's too cold and dark outside and I wouldn't like to get a cold right before my holidays). I will keep the (nearly) full front grill block (the turbo isn't blocked). The maintenance has been done one week ago : noticeably 5W40 oil and filters.

For each travel I'll avoid highways and depending on conditions I'll try to drive at 44-50 mph on the 56 mph roads. I'm currently trying to prepare the travels on the paper. I'm trying to avoid the mountains, but I may not be able to avoid all the traffic, noticeably around Xmas.

The first travel, next week-end, is to go from Leguevin to Roquebrun and back to home :
from:Léguevin, Haute-Garonne, Midi-Pyrénées, France to:D6113 to:Roquebrun - Google Maps
  • 121 miles in 3h18 = 36.6 mph
  • and back through same road...

The second one, during Xmas' week, is to start from Leguevin, go to Anglet then Marmande, then back to home :
from:Léguevin, Haute-Garonne, Midi-Pyrénées, France to:Anglet to:Marmande to:43.838489,0.395508 to:Léguevin, Haute-Garonne, Midi-Pyrénées, France - Google Maps
(the green part in the NW is the biggest forest in France, in which I grow up :) )
  • 163 miles in 3h59 = 40.9 mph
  • 128 miles in 3h18 = 38.8 mph
  • 108 miles in 2h49 = 38.3 mph

Times and distances are from my (GPS) navigator with a maximum speed of 50mph.

Total distance is 641 miles (who said it's missing 25 miles ?).
Total burned diesel should be less than 9.7 gallons at 66.6 mpg.
On highway with speed lower than the posted speed limit of 81 mph it would have been 13.1 gallons at 49 mpg, so a "waste" of 35 kg of CO2.

The first thing to do to save gas, is to wish to... and this will be a mental challenge.

I have seen low cost diesel at 0.999 €/L (4.809 $/g) today : cheaper than last year... but this will not refrain me from attempting this challenge :turtle:


MetroMPG 12-06-2008 07:07 PM

Denis - good luck with your devilish goal. I'll be watching here for updates.

groar 12-26-2008 06:47 PM

Lessons learned
I didn't pass the finish line yet, but already learned a few lessons. Some are only confirmations for me, but others are brand new.

Confirmations :
  • Inflate your tires at max sidewall and the car will coast forever... I love the feeling to coast in neutral in city :)
  • Limiting its max speed will save fuel.
  • Safety & courtesy (per ex keeping a higher speed than what DWL permits you) do impact FE, but they are non maskable rules. They are worse in mountain roads when your DWL max speed limit becomes the lower speed limit and make you a dumb cruise control...:(
  • I have to improve my drivings in mountain roads, even when I have no safety or courtesy constraint.
New lessons :
  • 5w oil do save gas. This is visible when coasting in neutral. Before oil change the consumption was at 1.4L/100 (168mpg) when coasting in neutral at 60km/h. Since oil change it's at 1.2L/100 (196mpg) ie at least a 8% saving:thumbup:, at least when idling...
  • Following situations do hit FE :
    • Freezing or near freezing temperatures (3°C = 37°F)
    • High humidity (raining or fog)
    • Head and side wind
    In all cases, FE is lower and DWL is more difficult. Trying to optimize the FE generates an higher deceleration which will need an stronger acceleration that will eat more than what was saved:(.

The rules I'm following are :
  1. safety and courtesy are unmaskable rules
  2. do not pay for more than 80 km/h (50mph) except if offered by gravity
  3. pulse 'n coast in neutral in cities (45-55 km/h 28-34mph)
  4. DWL out of cities (>60 km/h 37mph) : max FE of 4.0L/100 (58mpg)

With all these descriptions, 3 people and tens of Xmas gifts, you guess correctly that I will not achieve my goal of 66.66mpg, but I'm currently at my best tank with 4.45l/100 (52.82mpg) and my Xmas challenge is currently at 4.37L/100 (53.82mpg) which is my best trip result.


PS thanks for table support, I will use it to publish my results.

groar 01-04-2009 09:05 PM

The Roquebrun challenge
Short story : totally failed, but permitted me to learn.

My result is the following :

trip km L L/100km miles g mpg conditions
way up 203.2 9.8 4.823 126.3 2.589 48.78 6-4°C (42-39°F) - humid (>85%) - 30km/h (18mph) head wind
way back 213.5 11.1 5.199 132.7 2.933 45.25 3-1°C (37-33°F) - raining - 30-60km/h (18-37mph) side wind
challenge 416.7 20.9 5.016 258.98 5.52 46.9

With this raw result I lost :( but what's if...
  • I would have taken the highway :

trip km L L/100km miles g mpg note
highway 452 22.1 4.9 281 5.85 48
realistic highway 452 26.7 5.9 281 7.05 39.9 On such road (mountain) I would have done more than 6L/100 (less than 39) so I use my Combined EPA as reference
virtual 452 20.9 4.62 281 5.52 50.87 Highway distance with real consumption
Saving . 1.2-5.8 . . 0.32-1.53 . 5% - 22% ie EPA+6% - EPA+28%

Even in comparison with the unrealistic Highway EPA, I would have saved (a very little) gas :)
In comparison with a more realistic EPA and my old habit to take the highway at highway speed, I saved 28% :cool:
  • I would have driven a prius on the highway :
A prius generates 104g/km of CO2, which corresponds to a diesel consumption of 3.91L/100 (60.2mpg)

trip km L L/100km miles g mpg notes
prius 452 17.7 3.91 280.9 4.67 60.2
saving . -3.2 . . -0.85 . -18% CO2 :(

So I generated 18% more CO2 than an average driver in a prius.
Well, not so bad for such conditions (mountain, humidity and wind) ;)

If I can graph the altitude then I'll post it.


All times are GMT -4. The time now is 06:18 AM.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright