Drive Time/Distance for most efficient MPG

<div class='quotetop'>QUOTE(Tom 6850 @ Mar 11 2007, 01:22 PM) [snapback]403724[/snapback]</div>

That's easy. I find fuel consumption to be best when I don't use my Prius at all, just leave it parked

Here's a photo of my EV for city travelling. It never needs charging!


(Sorry, couldn't resist)

 

Short trips on a cold engine are among the worst conditions for good fuel economy. The Prius may take ~10 minutes to reach full operating temperature, longer in cold weather. Your FE in the upper 30s is not unexpected, though still respectable given your situation.

A couple of suggestions: Combine trips when possible (e.g., multiple errands), and consider an engine block heater. I had my heater installed a week ago, and since then my first 5-minute segment on a cold engine shows ~30-45 MPG, versus 25 or less previously. Your situation would seem like one most suited to an EBH. See this thread for a lengthy discussion.

 

Hi Tom,

You might also consider and EV Switch.

 

<div class='quotetop'>QUOTE(JimboK @ Mar 11 2007, 03:01 PM) [snapback]403744[/snapback]</div>

Seriously people, consider NOT using your car for short trips, even if it's a Prius.

 

<div class='quotetop'>QUOTE(lowlander @ Mar 11 2007, 10:10 AM) [snapback]403793[/snapback]</div>

Uhh, for some people it's not an option due to poor public transportation esp. if we need to carry things beyond what's practical on a bike.

You should try coming to the Almaden Valley area of south San Jose, CA sometime. There's no light rail near me, no trolleys, no subway and only the bus. The only bus that comes near my house comes once an hour on weekends and once every 30 mins on weekdays. Sometimes, the bus doesn't even stop at the bus stop. I know this pain because that's about my only means of transportation to go somewhere "far" while in middle and high school before I could drive (and while my parents were at work).

The closest supermarket for me is 1.9 miles away. The next closest is 2.6 miles away. The closest shopping mail and large retailer (not a drugstore and not a supermarket) is 6.8 miles away. To take the bus to the 6.8 mile away retailer is quite a trip via the bus and quite time consuming.

 

<div class='quotetop'>QUOTE(lowlander @ Mar 11 2007, 12:10 PM) [snapback]403793[/snapback]</div>

Ditto on lowlander's premise. We have a bus stop 2 houses from our front door and it is still not practical all the time to take the bus or walk.

Mornings I've been walking to the grocery store for the must replace weekly items, e.g. bananas and milk. However, for example, there is just no way my wife is walking home after work or commuting carrying a 5 pound computer after a 12 hour day, this particular trip is one of our longer ones, 3.7 miles one way.

getting back to OP's question ...

Great question Tom, I've been experimenting for about a year now, here's my observations,
First: You can still make short trips work if you can find a first five minute route that is predominantly a descent. It is not unusual for me to do 50+ on the first five minutes going down Glen Canyon, as the name implies it is quite a descent and only about a 1/2 mile out of my way detour. Couple that with a warm engine coming back and I lose only about 1/2 mpg going back up the canyon on a 100+ mile tank. Obviously much worse if I just filled the tank! Of course the net-mpg varies depending on the rest of the days trips, but this is something to consider upon developing a style of driving the first 5 minutes.

Second: If you're running errands anyway, I try to pick the first errand a good 5-7 miles away, which for me would be using the freeway for about 3-4 of those miles, hence a good warm up. That is, make your longest trip first, then do stop and go errands on the way back home. Couple this with thinking smarter before leaving the garage and this has kept me in the 38-42 mpg range consistently.

Lastly: To answer your "minimum distance" question specifically is tougher, because speed has a lot to do with that and obviously terrain. For instance if you do the first five minute gradually up hill for 4 miles you could be doing 25 mpg the whole time at any speed. I've done that coming back home from the beach or zoo! From my real world examples above I find it hard to believe that anyone could do much worse than my mileage, (numerous stops and hills), so I'd hazard a guess that your magic number is a 10-15 miles minimum for driving under 42 mph, and that this would yield easily low 45+ mpg.

EDIT: I'm really sleepy but the following spreadsheet shows possible scenarios of 10-15 mile 20-30 minutes trips, by all means check my math. But these are typical real world trips for me on and off freeway, etc.
EDIT: that should read "mpg total trip" in chart

 

<div class='quotetop'>QUOTE(Tom 6850 @ Mar 11 2007, 08:22 AM) [snapback]403724[/snapback]</div>

You may want to consider route-planning so the very first trip of the day is done at the slowest, practial speed while the ICE warms up. In my case, I wander through my neighborhood at speeds of less than 25 mph for the first 1-2 miles, depending upon ambient temperature. Thereafter, drive the car in 'hybrid normal' mode:


By hybrid normal, I mean 38 mph and below or for longer stretches, 48 mph and above. Avoid braking and otherwise, driving as calmly as conditions allow.

GOOD LUCK!

Bob Wilson