Why not figure it out? I'd be curious to know what you do get.

There is a certain level of inefficiency in shutting down and then restarting the engine, and also it takes X quantity of energy to move a vehicle a certain distance. If you can coast a high percentage of the way when taking the trip one direction, it might be mostly downhill. I'm betting that you can coast most of the way both ways.

If your car normally gets about 30 - 35 miles per gallon, I'd bet that this driving method might bring that up to 45 - 50, but probably not more than that.

Usually I come the other way in the daytime, so there is more traffic whose progress I'd interfere with if I were moving quite slowly, especially since quite a large proportion of drivers around here seem to think that ten miles or so over the speed limit is about right.

I haven't kept track as often, but have made about 13 of the 20 kilometres a couple of times.

I think that I'll try running with less variation of speed, which means that I will get lower mileage, I'm fairly sure - but I'll be doing less speeding up rather quickly, in a low gear, into the bargain. Both of which are cause much more rapid use of fuel.

The issue is how much fuel is used, not how many miles/kilometres I can run with the engine off.

Keep treading as lightly as possible on the earth, all.

ole joyful

Yes, I agree that the issue is total fuel used.

My guess would be that less speed variation would help, not hurt, your mileage.

Every time you touch the brake pedal, you turn forward momentum into heat. The wastes energy. Also, the faster you go, the more wind resistance there is, and the more energy it takes the push the car any given distance.

Speeding up rapidly, while it does use a lot of fuel when you do it, would also reduce the engine's total running time, and also would tend to operate the engine in a fairly efficient mode (producing a high percentage of it's full rated output) so it's hard to say which would be better.

Again, I'd really like to hear what type of fuel economy you can compute on this trip. I read many years ago in some car book that basically what you are doing can be a technique for getting to a gas station if you find yourself almost out of fuel and far from a station. They said to accelerate quickly to 30 or 40 mph, then shut the engine off and coast as far as you can, and keep repeating that.

By the way, many new cars do provide this type of "fuel-free driving" functionality without even turning off the key. Many fuel injected cars have fuel cutoffs that completely eliminate fuel going to the cylinders under many coasting situations.

Also, in Europe, there are "auto-start" options available on some Audi and BMW cars in which the engine shuts itself off instead of idling at stoplights, etc. Of course these also have fuel cutoffs and other fuel savings features. They do get better mileage than the standard versions of the car, but in most situations it is somewhere around 50 to 75 percent better. This is why I say I don't think you can get quite up to 100 mpg doing basically the same thing manually as these cars do automatically, but I do definitely think you'd see some savings.

I find that I can often coast 10 - 12 km. of 20 as I return home in the daytime, sometimes more, if I do not have traffic behind me.

When outbound late at night, and of necesity on my return in the day, I've tried to compress the variation of speed - rather than from running down to real slow (when there's no traffic to interfere with) to restarting about 25 then going up to about 40 m.p.h. (40 - 60 km./hr.). If I run faster at top speed, I run into more wind resistance, cutting fuel efficiency.

If I restart at very slow speed, I must operate in a low gear, which means that the motor is turning many more revolutions for each hundred feet travelled.

When I restart, I double clutch - first (quick) release to turn the motor over, then quickly push the clutch in momentarily (about a second, probably), to let the engine get up to speed before I connect it to the wheels again, to obviate the braking action of the engine as it builds up speed, causing reduction in speed on the road that would result. Some practice enables on to restart the engine with very little reduction in forward speed.

I rarely need to brake, as I have only two stop signs and have learned how to barely get to them. I'll run the speed down to very low just before I get there (and both are on a slight downslope, at the end of a bout 5/8 of a mile coasting.

I thought that, as I'd be restarting oftener, thus able to make less use of downslopes, that I would have lower coasting distance than when I let the car run down to say 5 or 10 m.p.h. before restarting, but I find very little reduction in the number of kilometres coasting.

Haven't figured a way to calculate mileage, though, unless I connect the gas line to a small container into which I've put a measured amount of fuel. Don't think I'm about to do that - for legal reasons (plus I have a slight inclination to laziness).

I just heard on the radio that we reduced fuel consumption over 25% back in the oil crisis in to '70s.

We've used much of the easily found petroleum resources - now it's harder and more expensive to find, and to extract.

When China, India and various populous countries build much expanded markets for fuel - guess where the price will go.

Further, it took millions of years for the oil to come into being - we've been using it for less than 100 years.

Seems to me our grandchildren will curse us for our profligacy.

Also, as a Christian, I feel that God has entrusted precious resources into our hands - and that we should not waste them.

ole joyful

To calculate your fuel mileage, fill your tank all the way up before leaving on your trip, and then fill it again when you arrive at your destination. You can then see how much gas was used by simply noting how much gas was needed to re-fill the tank.

Trouble is - there's a gas station about half a mile from the starting point, but I must travel nearly 8 miles to get to one at the second.

Also, one would want to ensure that the car was sitting at the same level when filling both times.

Actually, if I travel out, then back, I can refill where I filled before the outbound trip and, using the same technique while en route to the gas station, get a pretty clear picture - but limited to 25 miles.

Of course, if I could make the direct trip for three days in a row, without side trips, it would give a more precise result.

I'll need to do it soon, for they plan to wind the situation up about Thanksgiving Day.

For you U.S. people, that's always the second weekend in October, up in Canada.

Have a memorable autumn, all.

ole joyful

This project was operational until February of this year.

I could often coast just over 10 miles of the 12.5 mile trip outbound: something like 6 miles of the return trip, mainly due to increased proximate traffic.

Early this year Uncle's farm was sold and the new owner wanted the land but not the house, so said that I could use it - at rental rate much lower than in the city.

But the well that feeds the house is too close to the barnyard, so contaminated (it smells) that I use it for washing but not for cooking or drinking.

The car just passed the 200,000 mile mark and has cost me a substantial amount for repairs.

Some other repairs will be needed quite soon and it has less than a year and a half of life left, for it failed the emission test in January and got a two-year lease on life.

So I am looking for another vehicle.

Prefer a small car, standard transmission, hatchback, low mileage (kilometrage?) if poossible.

If some of you Canadians in southwestern Ontario know of such a vehicle, give me a shout, please.

Good wishes to all for efficient use of our scarce petroleum resources - let's save some for our grandkids' use.

Oh, I forgot - I don't have any.

ole joyful