How I drive my car

When going to work, mostly, I travel by car. I should of course travel by bus more frequently but the meeting locations at work and the need for me to bringing one of the kids to school bias my preferences.

I have been logging my fuel consumption for the passed three decades. It has been my ambition to gradually lower the fuel consumption for my private travels, both in absolute numbers and as litre per 100 km.

The fuel consumption is measured by the amount that I fill at each tank stop. I addition I use the fuel consumption number reported by the on-board computer for comparing different parts of the distance.

I compete against myself every day. To do so I have invented some disciplines to help myself improve my driving:

a) Count number of times that I need to use the break.

b) Minimise the fuel consumed during the cold start phase.

c) Find the most fuel efficient route (rather than shortest or fastest)

d) Find the most fuel efficient speed (travel time) for my route to work

e) Characterise the car fuel consumption at constant speed, to reach speed, cold start, diagrams helps (I mostly do this once for every car once it is run-in)

Mostly, I run one discipline every week to get some statistics, except for the fuel consumption logged by tanking that I always run.

The fuel consumption in litre per 10 km of my 1600 kg Volvo V70 Diesel is 13% higher than for my 800 kg Toyota Aygo, Gasoline. In the diagram, data is displayed from driving to work (42 km from Diseröd/Romelanda to Arendal/Göteborg). The same principles of driving and fuel saving were applied for both cars. You also see data from a journey back and forth to Västerås 0.40 litre per 10 km performed with the Volvo, to reach such a value not only favourable weather conditions are needed, also extreme handling was applied out of which I can only officially recommend to use the maximum speed limit, in this case of 70 km/h.

It is highly modern to learn “Ecological Driving” today.

It is mostly taught to:

-Shift gears early

-Jump the gears, for examples 1 à 3 à 5

-Stay ahead of the changes in traffic

-Check tyre pressure, and keep on the high side

-Use the engine break to activate fuel cut-off when reducing speed

-Use down hill and up hill to optimise energy use

I use the same principles but I don’t jump the gears*. In the passed I have done some assignments that taught me some of the details of the modern engine control systems. I have therefore used some of that knowledge to ad further details to my driving:

-First I buy the right car for my typical travel (not for the extremes) or when I have access to several cars I use the right car for the right travel. I get a good hint from the data specification sheet. Usually the right choice is, lowest power and manual gear, unless you usually tow a trailer. For Europe, diesel is preferred for any traffic except extreme city driving.

-I take out all tools and gears that ad weight to the car.

-In the winter, rapid engine warm-up is achieved by using fuel burner for not more then 10-15 minutes

-In the winter, I don’t use the compartment heating, until the engine fully warm this usually takes at least 5-10 minutes (I dress properly). The same goes for heating of chairs, rear window, etc. I use them but to a minimum extent.

-In the summer I don’t use the air conditioner at all, unless the family rides with me.

-Downhill rolling is a delicate matter, depending on the event after the slope and on the decent, different methods come to use. If breaking will be applied after the hill I might as well use the engine break all the way to activate fuel cut-off. If the decent is steep enough I see to that the speed passing the top of the hill allows me to accelerate by declutching and rolling/sailing to recuperate the energy. Unless the slope is very modest I don’t use the gas when going downhill.

-Engine is shut-off at red lights (but mostly I plan the driving to avoid stopping)

-I avoid going faster than 90 km/h, the optimum speed is about 60 km/h for most cars (generally as slow as you can drive on the top gear)

-If I’m lucky to get a truck or bus ahead of me I optimise the distance to lower the aerodynamic losses

-I avoid taking over other cars

-When driving it’s my ambition to plan the driving to such an extent that it is not necessary to use the break. The average number I use the break on my way to work is 4 times. But, not rarely, I only apply it once, when stopping at the parking lot.

-When possible for my daily schedule, I stop at the park+ride and take the bus!

*In theory it’s OK to jump the gears but I found that for my cars and traffic it is better to keep the engine at low speed and to apply even earlier gear shifting. In case the rout is disturbed by unexpected changes in traffic I’d like to have the engine running as close to optimum revs as possible, i.e. lowest possible engine speed.

About volvobuses

Adjunct Professor of Catalysis at Chalmers University of Technology. Lives in Gothenburg, Sweden, with my wife and three daughters born in 1991, 1994 and 1997. Is a passionate runner.
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