The economic incentives of fuel efficient driving.

[Fr3AkAzOiD]

My comute is almost all 55 mph speed limit and a 75 mile round trip.

The other day I needed to get home in a hurry (highly unusual) so was driving 7 mph over the limit, droping to third gear at 60 mph to pass people, All that impatient jazz.

Due to the car mods I still ended up getting above 40 mpg.

My normal drive would have be going 5 under the limit and getting around 52 in the same temps.

In the end it took 40 min to get home instead of 50 but taking that 10 extra min each day saves me $35 a month easily.

[Frank Lee]

Originally Posted by roflwaffle

What's your mpg at 55mph and at 70mph Frank?

It has been so long since I've driven 70 for any distance, that I don't know the fes.

[euromodder]

Originally Posted by roflwaffle

-What is the difference in highway mileage between what you get driving efficiently and what you get driving like everyone else?

For driving like everyone else, I need to go back to before July 2008
In July 2008, I slowed down by 10km/h (6mph) to 110 km/h (68 mph) instead of 120 km/h (PSL).

FE @ 120 kph was around 5.5 L/100km - 42.8 mpg indicated.
FE @ 100 kph is around 3.5 L/100km - 67.2 mpg indicated - but it's now consistently reading low.

Overall, so not just highway though I do most miles on the highway :
Before July 2008, I got 5.89 L/100km - 39.9 mpg.
Since joining ecomodder in July 2010, I'm at 4.91 L/100km - 47.9 mpg.
Since Jan 2011, 4.75 L/100km - 49.5 mpg.

-What is the difference in average highway speed between what you get driving efficiently and what you get driving like everyone else?

On my commute : apparently none at all.
I'm still seeing similar averages as I got in 2008.
The extremes seem to have been reduced though - the averages are now more average.

The best indicator :
I still leave home around the same time, and arrive at work around the same time. Going back, it's usually the same.
The variations are mostly due to the shifts I've been working.

[bwilson4web]

Hi,

This is my first mph vs MPG chart and it shows two knees in the curve:

This chart of 1.5L, NHW11 mileage came from gas receipts when I was topping of the tank twice a week.

The two knees are:

• 65 mph - anything over this speed and mileage takes a dive. At 70 mph, it is 49 MPH but hills and headwinds really take a toll. A 5 mph guard band minimizes these effects.
• 38 mph - at 40 mph, the city mileage takes a serious dive compared to just a few miles per hour slower. The Prius has a critical transition speed, 42 mph, so having a 'guard band' avoids this bad speed. Or driving 46 mph, puts the car above this critical speed and into another efficient band.

Route planning is also important and this takes experimentation. I was using my wife's 2001 Echo until we got the 2003 Prius:

Not shown are the different routes tested but the key is the Echo does best by avoiding stop-and-go traffic. Both cars benefit from a slow-speed, neighborhood warm-up. In contrast, the Prius does great in stop-and-go which means I can use short-cuts that would negate the Echo mileage as it heats the brake pads.

Both cars have nearly identical sized tanks so direct and indirect costs:

• Echo - fill-up every two weeks.
• Prius - fill-up every three weeks.

Bob Wilson

[BHarvey]

My first ten tanks I drove like everyone else and averaged 31.2 mpg.

My last six tanks averaged 39.95 mpg.

8.75 x 15.4 gallons (my average required to fill up) nets 134+ more miles a tank.

75 mph = 35 mpg
55 mph = 45 mpg

It's worth it to me because I NEVER get in a hurry.
If I have to hurry, I just won't go.

[redpoint5]

Originally Posted by roflwaffle

~$4+/gallon, same as everyone else in the states give or take ~$.25/gallon. Going with your example, lets say I'm paying $8/hr at whatever speed. I go faster and get to my destination 15 minutes sooner than I would have otherwise and also pay $3 more in gas money. So, if I go faster I pay an extra $3 to cut 15 minutes/.25 hours off of my trip. $3/.25hours=$12/hr more to drive faster. Obviously every example depends on the specifics, but the basic idea is that you get whatever mpg at whatever reasonable lower speed (~55mph to ~65mph), and when you drive faster than this you pay $X more in gas and reduce your travel time by Y hours, so you end up paying $X/Yhr=$Z/hr to drive faster.

Gotcha, thanks for explaining how this is calculated.

Of course there is a point of diminishing returns because each mph faster takes an exponentially greater amount of fuel to maintain. I don't have solid numbers to work with yet, but my estimation is that my mpg at 60 is 35, and at 75 I get 30. That puts me at what, maybe $8/hr after taxes? Perhaps if I had a nice audio book to listen to I would sell that time for $8/hr.

Now, if cars could drive themselves and I could surf ecomodder while I took a snails pace home, I would gladly do so. Best ecomod- autonomous vehicles. It's moments like this that I realize I was born too soon.

[roflwaffle]

No problem. People aren't really familiar with marginal costs for things. In this case how much it takes to go faster.

Assuming $4/gallon for all of these and not accounting for taxes. Overall the TX to AL run that bwilson had from ~60mph to ~70mph is the lowest at something like ~$2/hour. Euromodder is at about $3/hour, and BHarvey is at about $5.25. Arguably driving slower in those cases would only be economically worthwhile if someone either had to pay a lot more for gas (euromodder?) or they like driving a lot more than they like working (I do at least).

[euromodder]

Originally Posted by roflwaffle

Arguably driving slower in those cases would only be economically worthwhile if someone either had to pay a lot more for gas (euromodder?) or they like driving a lot more than they like working (I do at least).

I do pay a lot more than 4$/gal (US) - more like 7.35 USD / gal.

My commute has become slightly over 100km, so using almost 1.5L/100km less than in 2008, I use about 1.5L less per day than I would have used @ my pre-2008 fuel consumption.

That translates to 1,96 euro or 2.91 USD per working day.
And I don't appear to be losing (more) time doing so.

On the motorway I often pass people who had overtaken me before, as I don't slow down when they do and my merging strategy is clearly better for keeping up momentum

[jamesqf]

Originally Posted by redpoint5

Perhaps if I had a nice audio book to listen to I would sell that time for $8/hr.

Check out your public library. They probably have many that you can download. I recommend the Arkangel Shakespeare series. Got into it a few years ago when I was doing 5-6 hour drives once a week. Music tends to make me sleepy after an hour or two (as do the audiobooks that're just read by one narrator), but something like that with some plot & different voices helps keep me awake. Also look for BBC/NPR radio programs, etc.

[justjohn]

You can get tons of audio books free on the internet. Put them on your mp3 player and boom, you're good to go.

The internet is full of awesome. Example:

A Christmas Carol as read by Captain Jean-Luc Picard