Route conundrum...
 

I'm new to eco driving... I hope someone can advise me. I drive pretty much the same route every day. There are many ways I can take to bypass traffic but only 2 ways I can get home from the freeway. One route is longer but doesn't have any traffic lights or hills. The other route is shorter has 4 extra lights (which are horridly timed!), a slight uphill grade and a rather large hill.

It might be an easy question but the shorter route is actually 3.5 miles shorter...If I get stuck at every light (which happens about 50% of the time) both routes take about the same time to complete. I'm hoping there is a way to take this in to account. I don't have anything to tell me instant MPG.


My question is how can I figure out if taking the long way is actually worth it or not?

I just did both routes and calculated FE at the end of each tank. I wish for me it was better to go to the highway, but the lower FE i get in city driving compared to Highway does not offset the difference of the actual miles.
The 2 ways for you would be to do it this way or hook up an MPGuino to your car to get the trip mpgs

Thanks for the reply :)

I was hoping to avoid driving the route for a full tank because of the error factor. I would have to drive the new route for several tanks to get the average which could take a long time and potentially waste fuel if it isn't "worth it" :(

I've read some of the MPGuino information and it seems like a cool gadget. However I have made a strict rule (to myself) that any eco mods I do would need to be justified by a ROI. For example currently if my vacuum gauge (driver mod) continues to net me +3 MPG it would take about 7 fill ups (about 2 months) to pay for itself. I know nothing ventured nothing gained but being broke sucks.

I paid $70 for my ultragauge and have already seen a full ROI. The problem with a vacuum gauge is its instant feedback. what we do with the gauges scangauge, ultragauge, mpguino is play a game where your avg fuel economy is your score and always trying to get the high score by keeping your foot off the pedal. It gets quite fun trying to beat your previous tanks. Scangauge and ultragauge are obdII though

I see what you are saying.

I have an app on my phone that tells me average speed... you think there would be a way to calculate which route is more efficient by that?

i say no for the reason being to get good mileage you want to be as slow as possible in the highest gear. Ie. i can already tell you city is going to be slower, but for most people highway gives better mileage. Now some people on here can get better mileage in the city versus highway as for the techniques used.

I have no doubt I would get better fuel economy going the long way but that also means about 35 miles extra per tank...

I figure if I used the exact same fuel going either route and I get 25MPG going the shorter route does that mean I have to get greater than 28MPG in order to actually save money?

does that sound right?

I nearly always choose the longer, but non-stop, routing.

Whether in my pickup or at work in the Peterbilt. FE is really just a way of showing lower fuel burn for the same work accomplished. In this instance -- routing -- the stop'n'go is detrimental to the rest of the vehicle (non-steady fluid temps, tire temps, etc) and requires more inputs from the driver.

Thus, while I travel a bit farther (there is a trade-off of miles versus savings at some point) I feel assured that the fewer stops/accelerations is the best course to take for longest vehicle life. And for the driver to retain as much energy as possible (this is not discussed, but vital to more than FE, it is central to safety).

That is the larger metric over FE -- vehicle longevity -- and the one that really counts. Once the vehicle is broken-in, we do not want any degradation from that point onwards. Longest life in tires, brakes, etc, is directly to that end as well.

.

I see what you are saying. I was hoping there would be some formula or rule of thumb... I think I will try taking the other route for a few weeks and see what sort of improvement there is. 17.5 extra miles per week isn't huge but could actually cost me in the end.

I also vote for the low-stress longer path. No hills? Fun.

Can you describe the paths a bit more? You say it's 3.5miles shorter, over what distance? What speeds? Just accelerating from a couple lights would negate any MPG gains from the shorter commute, IMO.

On my SGII / Civic I typically get about 55 MPG in the summer regardless of the route (<65mph intra-city routes that is) so I always choose a shorter route to get lowest number of gallons per trip.

BUT this is a skill I've honed with the SGII and I'm doing advanced hypermiling, DWB and extensive EOC, in a manual tranny. Without those techniques it's possible for a shorter city route to yield higher total gallons, although even being minimalistic, DWB and engine-off at lights, mpg shouldn't be too different between city and highway. Neutral-gliding or P&G on downhill also neutralizes the effect of the hill, even without EOC.

Hills and lights are mostly non-issues for me unless there is some loss that can't be avoided, i.e. downgrade too steep or a stoplight at the bottom of a hill or a downhill freeway off-ramp, requiring brakes or engine braking, etc. Even then it sometimes just averages out.

Eco-driving can be done wrong though. Owning a gauge is money.

There is a formula...how long is your route? you need to figure out the percentage...if the longer route is 5% longer and you can get 5% better fuel economy then you are breaking even...but if it's 5% longer and you get 10% better fuel economy then you're saving fuel.

I know you don't have instant feedback so it's hard for you to figure out what fuel economy you are getting on the different routes but i can almost guarantee it's always cheaper to go the shorter route

It's 27% longer. My daily commute isn't that far. It is 64% highway and 36% city.

but i can almost guarantee it's always cheaper to go the shorter route

The number of full stops is the killer. Not so much a penalty on the gasoline go-karts as compared to diesel trucks of any size, but it is still there. Wear & tear is cumulative over tens of thousands of miles. That is still the metric about saving money.

The heavy subsidization of fuel in this country makes chasing a few tiny tenths nearly meaningless. It's the cost of the vehicle over X-miles and Y-years that is the starting point. Extending the life of a vehicle over several more years is where true savings are found. Fuel cost is just one of a couple of variables under control of the driver. The rest is a fixed game.

.

I've put a lot of thought into this and I disagree on the economic bit. At least - in the context of the cars that I drive.

My Corolla in the 220k neighborhood:
$0.08 per mile repairs + maintenance over the last 33k
45MPG @ $3.6/gallon = $0.08 per mile (28MPG = $0.13/mile)

(I'm pretty sure the wife's Civic now in the 150k neighborhood has been significantly lower than that in repair $ per mile for the last 50k, but I haven't actually tracked it.)

(Razor never said it was about money. For all we know he wants to minimize CO2.)

Post #7 sorry...

Don't get me wrong though all of the emissions equipment has remained operational on this vehicle. I maintain and repair any that fault. So I am obeying federal law and doing my part to keep the EPA happy.

Another aspect to consider is the accident potential of each route. If you are trying to coast up carefully to keep an even speed, and avoid a full stop at any of the lights,
someone less patient will invariably have some kind of conflict with you.

Pennies difference will mean little if your car gets hit, or if you are constantly being
flamed by other drivers.
I think it is easy for you to see I vote for the longer road with peace of mind!

Well after 3 tanks the vacuum gauge has net me an extra 1.5MPG average. I went ahead and ordered a MPGuino from JellyBeanDriver. I have the ability to datalog right now but there isn't any real time easy numbers I can look at for efficiency other than the injector pulse width.

Something else I did was to install a brake light button for 2 reasons... 1 people here get right on your ass and don't pass you. I can hit that button a few times to act like I'm slowing down so they get in the left or center lane. The other reason is engine braking. People in their automatics don't know what that means and plow in to the back of you. When I exit the freeway I can engage DFCO and push that brake light button.

Here it is...
http://i108.photobucket.com/albums/n...-38-11_481.jpg

When the brake lever is down I just rest my hand on the hand brake and push the button.

What is your typical speed on the short route, excepting having to stop for lights or slow for traffic?

The trick is to stay in a relatively high gear for as long as possible. If you are at near highway speeds (above 40 MPH) for most of the short route, that is the most economical option - even though the long route may be less stressful driving.

The short route is 2.1 miles. Average speed over the short route in a 15 day spreadsheet record is 19.6MPH @ 6 minutes 25 seconds. This was calculated by taking the average of the speeds and times over the 15 day period. This route includes 5 stop lights that are poorly timed, a small ascending grade and a large hill. I can time the lights but it takes a lot of throttle which is inefficient.

The long route is 5.7 miles. The average speed over the long route is 41.6MPH @ 8 minutes 13 seconds. I only have 3 data points so far (3 days). This route has only 1 stop light. There is a small descending grade initially then it flattens out the rest of the way.


I can keep a much higher average speed here but it takes about 2 minutes longer and I have to travel 3.6 miles further. It might not sound like a lot but it is more than two and a half times the distance of the short route.

There is another factor to consider. Since this is such a short distance your car may not be coming up to full operating temperature. In that situation it consumes more fuel due to fast idle, etc. The long route might allow the car to warm up more since it takes longer.

I wouldn't be surprised to find there is no advantage to either route. You might want to use the hill you mentioned by taking that route in one direction only, to give you a downhill advantage. The shorter route is fewer miles traveled, but the longer route may yield better MPG. Sometimes you just can't win...

The vehicle would be at operating temp. Maybe I forgot to mention the commute home involves about 9 miles of freeway travel before I get to the point where I could take the 2 ways.

Funny how we can forget to mention everything that might be relevant to the situation...:rolleyes:

I was trying to be polite. It was mentioned in the first post. ;)

No, apparently you mentioned driving on a freeway in a cursory way, but you never mentioned 9 miles or any distance traveled on it. Maybe you thought you mentioned that, but you didn't.

Being polite may be nice, but it solves nothing. Providing all relevant information in an accurate way is more useful to solving a problem. ;)

Rhetorically,

Does this include all repairs and maintenance? Nothing broken or malfunctioning, correct? All up-to-date according to manufacturer service schedule?

Most folks will dial back on these expenses, reasoning that the vehicle is nearing end-of-service (for their purposes). The problem is that some will trade the vehicle when the carpet gets dirty and others not until both the trans and engine fail simultaneously.

The only fair comparison (between vehicles) about "economic costs" is in keeping the thing as near-to-new as possible. And the numerical comparisons are in maintenance/repairs on a cpm basis.

Those who have a stable of old cars have to run the numbers together for all of them. And still account for, or justify, delayed maintenance or repairs.

CPM calcs are either on the money or not. What I have spent can be considerably different than what I should have spent to meet the same criterion.

The longer route can be the better choice by a factor. The details that make it so are what need investigating.

.

I second this. I am on my first tank of REAL eco driving in my Mustang GT (4.6 V8). I know that I'm only half way through my 1st tank but comparing it to previous tanks I have gone from 4.90g/100m (20.4 mpg) to 4.18g/100m (23.9 mpg). My last 10 tanks going back to early August were 20.8, 20, 20.4, 19.3, 20.6, 20.8, 20.3, 22.7, 21, 22.3. I think I'm off to a good start in below 40 degree temps on winter gas.

I'm driving the mostly same route as before because I'm an unemployed full-time student living on student loans. My only driving is to the Safeway and to my GFs place.

All I did was take out the CAI and re-installed the stock airbox with my ultraguage and play "beat the number" every time I drive. The hills are steep enough that I can coast in neutral for a quarter mile (or more) on local roads and highway. On the local roads, shifts at 2k with a skip from 3rd to 5th. Highway driving capped to 5 over the limit. No EOC at all, anywhere.

I drive about 5000 miles a year in the car (another 3000 on the motorcycle when the weather gets warm) and if I keep this up, I will save about 36 gallons a year (245.0 - 209) and at current prices that is about a $115.