Driving strategy for short trips (5-6 miles) with cold engine

<div class='quotetop'>QUOTE(Luc Declercq @ Aug 3 2006, 03:02 PM) [snapback]297213[/snapback]</div>

I asked that question once and the two answers that stuck in my mind were:
1. ride a bike
2. take a longer route

I have found that the driving tips most often quoted do have quite an impact in the middle of my commute, virtually flat, even for short trips. The first 5 minutes isn't always in the 20's due to warmup, I believe it is the combination of using the iternal combustion engine and first five minutes, that is some days I can pulse/glide a lot for the first five minutes and that segment is decent, but it depends on whether I'm going home or going to the Univ.

 

It's actually surprising what a different route can do for ya... I decided to try a different one to and from work (about 7 miles each way) this week. only takes me 2 minutes longer, there's less traffic, and only 2 traffic lights (instead of the 2 dozen on the old route). anyways, i saw an increase of almost 5 MPG versus the old route! not to shabby considering i was already getting high 40's.

Also, it would appear that you're relatively new... give the prius a little time to break in. you'll see the mileage start to increase a bit between 5k and 10k miles on its own.

 

i now have a commute of 5.6 miles as well and most a gentle uphill after a short severe downhill. but the speed limit is ½ 25 mph, and ½ 35 mph.

i pick is to drive it. if you cant lengthen your commute,(NOT recommended) find a route that has lower speed limits. the distance is short enough that it would not impact your commute time greatly.

time of day will be the most critical here. i am lucky as i am on the road at 5 AM with minimal traffic going to work up the grade. i come home thru downtown Olympia at 5 PM with heavy traffic but going down the gentle hill so multilpe stops and go's dont hurt as much.

typical tank mileage starts at say 61.5 mpg in the morning, drops to 61 when i get to work, then rises back up to 61.5-6 or so on the way home.

 

Please pardon the snarky comment here, but drive farther just to see your MPG go up?!? Please.

Let's say your normal drive is five miles, and you get 45 MPG. Five miles at 45 MPG uses 0.11 gallons of fuel.

Now let's say there's another route, just a mile longer, that somehow takes your mileage to 50 MPG. Six miles at 50 MPG uses 0.12 gallons.

This saves gas and cuts emissions exactly how?

My new Prius is running just under 40 MPG for my 2.5-mile commute, but I only have 1100 miles on the car (just got my first 50 MPG partial fill-up yesterday - yay!). I usually walk to work, but sometimes I have to have a car for "things". It's still a tad wee bit better than the 12.2 MPG I get in the Suburban for the same commute.

There's not a whole lot you can do to improve your situation. I'm not by any means an expert on the running stages of a Prius, but the statistic I see most frequently here on the chat site is that it takes five minutes to warm the engine completely. For my short commute, the way I view it is that I'm doing my part as best I can (though for me it's 99% related to my wallet), and the savings I get for other driving will more than make up for less-than-"perfect" results on short drives.

 

<div class='quotetop'>QUOTE(glenhead @ Aug 4 2006, 09:35 AM) [snapback]297645[/snapback]</div>

Of course, it really is about saving gallons! LOL, but it is an interesting point of discussion making the commute longer, in my case I could drive the perimeter of SF and still not have more than a 25 mile commute! So yeah, it is really a lousy solution for the environment, wallet and life (assuming there's more to life than sitting in a Prius getting high mpg LOL). It really is only a solution for higher mpg.

The first five mnutes is interesting, I've tried different routes to optimize this segment and it isn't unusual to get even above 75mpg, going real slow gentle downhill at 6 AM, but work life usually starts at 9 AM! I have simply found no other way to compensate for living on the tallest moutain in SF, given a real commute of 3.6 miles one-way.

However, Luc, I'm really intrigued by the EV switch, hmmm! Tell me more!

 

i agree, you souldn't go out of your way to make the commute longer. however, if there's an alternate route that is less crowded, less prone to stops, but happen to be a slower speed limit thus it takes longer (and is maybe 1 city block longer in distance), isn't the added peace of mind and mileage worth it?

 

<div class='quotetop'>QUOTE(glenhead @ Aug 4 2006, 09:35 AM) [snapback]297645[/snapback]</div>

I remember a thread on whether we should measure miles per gallon or gallons per 100 miles, which one was philisophically more correct. I think the best answer is gallons per month. Consumption is more important than economy.

That being said, I've noticed a huge difference between winter and summer, altho I've yet to go thru a full year of seasons. When I got the car it would take about 1/3 of the drive (7.5 miles) to warm up, with temps in the 20's (F). Now with temps in the 70's in the AM, I can get into a glide on the far side of the block. It's still not fully warm, but it's definitely better. But today I biked (finally cooled off!), and that uses 0 gallons (not including negligable gas needed for increased food consumption).

I think having a warm garage would be the single biggest factor for reducing engine warmup time, but that uses it's own resources, unless you have a passive solar system). I'm interested to know if there are driving techniques to help reduce gas usage during warmup time (this discounts racing the engine needlessly).

 

I HAVE chosen a longer route to and from work (2 different routes, in fact) since I got my Prius - my former 5 mile commute is now 6 miles and perhaps 3 to 5 minutes longer. But I'm not doing it for the mileage - I'm doing it to avoid the very dangerous intersection where my old car was t-boned in April, and a second almost-as-dangerous intersection that's nearly blind now that the trees have leaves again. If the town every installs a 4 way stop sign at the most dangerous intersection, I might start taking the 'shortcut' again during the fall, winter and early spring.

There's another instance where I choose the 'long way around' option. When I go to visit my son in western Massachusetts from New Jersey, I now take the New York State Thruway almost up to Albany and then get on I-90 going east. It adds about 20 miles to my trip, but it avoids stop and go traffic through much of Connecticut. I have chronic back problems, and when I used to drive up through Connecticut, I'd arrive barely able to walk, and sometimes had to stay a day or two longer until my back was ok for the drive home. The 'long way around' saves me at least half an hour on the trip compared to 'good' conditions on my old route, and probably means I use less gas on the entire trip, since I'm not stuck in that stop-n-go traffic.

So don't necessarily sneer at the concept of 'a longer route'.

Another tip - combine errands with your commute home. I used to go home from work, do some things and then go out later for errands. Now I get groceries, go to the post office, etc. without stopping at home first.

 

<div class='quotetop'>QUOTE(Jeannie @ Aug 4 2006, 11:06 AM) [snapback]297698[/snapback]</div>

There's no way I'm sneering at the concept, I'm pointing out that taking a longer route cannot, outside a very limited radius under limited circumstances, save gasoline or cut the emissions generated by burning said gasoline. There are several routes I use, especially in the Ft. Worth area, that are several miles farther than taking I-35W through downtown with the wackos. I know that I can save twenty minutes and lots of aggravation by doing so. I'll even go ffifteen miles out of my way to go around Oklahoma City rather than suffer through the interminable construction therein. I'm all for taking alternate routes when it can keep me from shooting the dog when I get home, but longer *usually* means more gasoline.

 

<div class='quotetop'>QUOTE(nerfer @ Aug 4 2006, 10:48 AM) [snapback]297687[/snapback]</div>

Hey, watch those emissions! ... Oh, you mean gas to the grocery store, sorry, LOL

<div class='quotetop'>QUOTE(nerfer @ Aug 4 2006, 10:48 AM) [snapback]297687[/snapback]</div>

Here in the city most homes from the 40's still have the forced heat furnaces, the ones with the 12"x12" burners, or thereabouts. These keep the garages to around 60F easily. Not very efficient, but very common.

<div class='quotetop'>QUOTE(Jeannie @ Aug 4 2006, 11:06 AM) [snapback]297698[/snapback]</div>

Actually I think you've just added an important clarifier to the equation = shouldn't go out of your way to make the commute longer save gallons first.

You are rightly clarifying = don't go out of your way to make a safe (healthy & sane) commute longer, save gallons first.

 

My commute was a 8.9 mile commute with a short 35 mph (.8mi) followed by a 5.7 mi 50 mph part and then the rest at 40- 35 mph. The new commute is a rolling hills commute with less total change in elevation. All of this is 35 mph or less. The total is 9.2 miles. It has made a huge difference. I have gained more than 10 mpg by not going on the higher speed route. I can not keep the car in stealth mode at 50 but I can at 35! There are at least 3 other routes I could take and this appears to be the best for total gallons. Route is important. Total elevation change is important. Speed is important. Also I have a block heater. That is critical for short commutes. My commute will always get me in the S4 coolant temperature range even on the "coldest" days we get here in the PNW in winter. With the block heater I am at that in one block in summer and in 3 blocks in winter.

 

<div class='quotetop'>QUOTE(berylrb @ Aug 3 2006, 08:46 PM) [snapback]297489[/snapback]</div>

Damn. You removed my typical snotty response. You've left me nothing!

 

It's no mistake that nearly every list of tips for lowering fuel consumption out there (for all cars) lists combining trips as a top strategy. It's only because of our 5 minute interval graphs that we see the fuel cost of warming an engine so clearly. It's really there for all cars, even more so with large iron engine blocks.

What our MFDs don't show us is the additional costs of driving a cold engine in terms of nasty carcinogenic emissions, greater engine wear from reduced lubrication and thermally altered gaps, and corrosive combustion byproducts in your oil eating away at your engine.

No, driving farther won't lower any of these costs, but linking trips when possible to reduce engine warm ups (and maybe even total miles driven ) will help with fuel consumption, pollution, and engine longevity.

 

<div class='quotetop'>QUOTE(theorist @ Aug 5 2006, 12:09 AM) [snapback]298136[/snapback]</div>

<Prius owner feeling terribly guilty as he climbs in car for third time today to buy some candied peanuts>

damn, damn, damn ...

<Prius owner feeling better that he can add a trip to the hardware store to get a house key made for dogsitter>

, ,

<div class='quotetop'>QUOTE(Luc Declercq @ Aug 5 2006, 04:51 AM) [snapback]298162[/snapback]</div>

Yes absolutely, longer=alternate of whatever length to save gallons.

Why not EV switch for the first mile?

What is the range of temeratures where a block heater is a fuel-saver?

 

<div class='quotetop'>QUOTE(berylrb @ Aug 5 2006, 06:20 PM) [snapback]298463[/snapback]</div>

I think the question is how long to use the block heater for a given temperature? We have a moderate climate and 3 hours in winter appears to be enough and one and a half in the summer, unless there is a heat wave. It is a matter of getting the ICE up to temp

 

<div class='quotetop'>QUOTE(hdrygas @ Aug 5 2006, 11:09 PM) [snapback]298509[/snapback]</div>

I thought a gasoline engine is incredibly efficient if you want to create heat and mechanical energy. Wouldn't using block heater this much save gallons of gasoline but use more total energy? I should probably look for old posts here on this. I thought they'd be out of season.

Do any carefully engineered plugin hybrids use an integrated, programmed block heater in moderate climates and even summers?