Longer route with steady speed vs. short stop n go route
 

I've got 2 routes I can take to work, the first is 11 miles and starts out with a nice gentle 2 mile slope from about 500' to around 50', after that the route is full of undulations in the grade of the road, and a fair deal of stop lights. The last mile or so goes from 50' up to 400' and is quite steep but unavoidable no matter what route I take. The speed limit is 35 the whole way and it's pretty heavily trafficked on my drive in at 1:30 in the afternoon. There's been ongoing utility work and repaving for some time at night so I've avoided it for the most part.
Route 2 is I-5 and the I-205 belt route. Its considerably longer at 17 miles but traffic is always moving and the speed limit is 55 for the first half so I don't irritate many people. The I-205 stretch goes up to 65 but trucks are limited to 55 so I generally hang in the right lane and let them act as wind breakers ;)
I've done some very basic measuring of each route on a tank to tank basis but it's not really the most accurate since I do drive more than just to work and back. At least from what I can tell the freeway yields much better mpg but it's also a longer stretch. The road on the other hand is pretty unpredictable and also includes 2 railroad crossings.

You need a OBDII gauge! It makes driving fun and you will know for sure.

I would take the longer route and keep to the right lane. And around 40-45MPH as much as possible in your automatic. Top speed 60MPH. (don't fight the wind)

I wouldn't take the red-light route unless you can time the lights and hit all green.
(almost impossible, around here at least)

When I get in my car and drive somewhere I try my best to keep it moving until I get to wherever i'm going.

I've got some tax return money earmarked for an ultragauge :)
The lights are on timers through one town, then the rest are all sensors. I get lucky for the most part at night since there's hardly any traffic when I'm off work at 10:30 but the construction has been a real slow down lately.

I'd still consider the shorter route. Even if you get much worse fuel economy, its just that much shorter. You said you just got 26 mpg on your last tank. If that was taking the shorter route, you'd need to get over 40 mpg on the long route to make up for the additional gas usage. Now, this is possible, but as dirtydave said, you need a gauge to tell you for sure.

Stoplights and 35 mph limits are a hypermiler's playground. Rock that short route!

Don't listen to me, those guys are right! I changed my mind!

In addition to the fuel consumption, you also need to consider the wear and tear on the car's engine, transmission, brakes, and tires from driving either route. The shorter route with its stop and go driving and having to run up through the gears multiple times during each trip would produce more wear on the car's equipment. The longer route with its fairly constant speed and mostly low engine loads would be better for car longevity.

If you get 32 MPG on the freeway route and 26 in the city route, you should be using the same amount of gas, since the freeway is 6 miles longer, you need 6 more MPG to make up for the gas. Another thing to account is how the construction and railroads will affect your gas mileage. In my city, whenever there is a train, you will be sitting for at least 5 minutes, which is a pain in the butt and can cause excessive idling. Even if the city route for me is shorter, that doesn't make if faster or as fuel efficient.

Something that I have noticed about myself when driving around town is that I get aggressive and impatient in city driving, but on the freeway I get calmer and more patient. Find out which of these areas you are better at and stick to doing that. Most hypermilers try to stick to city streets because they can drive without the engine in those environments, but when driving an automatic you don't get as many opportunities to turn the engine off.

For what basjoos said, I think makes a lot of sense. Taking into account the load on the engine and transmission, stoplight to stoplight driving is pretty bad.

Like others have said, get instrumentation and track your statistics.

Sorry, not trying to be a jerk, but this math isn't correct.

11 miles @ 26 mpg = .42 gallons used

17 miles @ 32 mpg = .53 gallons used

These are not the same amount of gas.

To get the equivalent mileage you take:

.42 gallons / 17 miles = 40.5 mpg

Ah, sorry, my mistake. But getting 40.5 MPG on a freeway run shouldn't be too hard, honestly. For me I can 45+ MPG with 4 miles on the freeway. With more miles I can bump that 45 up to 50 easily, maybe 60 if I slowed down (I go 60-70 DWL, 55 is too slow for people around here).

I completely agree.

I took the shorter city route in to work today and had forgotten all the excellent coasting opportunities afforded. Until I get an ultragauge or similar I won't really have concrete numbers but if I had instrumentation it would be a lot easier to adjust my driving. The only downer is the traffic. The lights aren't too bad and I know how they're timed but add a bunch of mid day traffic and there's a lot of variables. My preference would be to take the longer freeway route to work since traffic is always moving and take the city route home at night when traffic is minimal. Until they finish the night work they've been doing on the road ill probably stick to the freeway. The rail crossings aren't a huge issue since I always shut off the motor as soon as the gates come down and don't start again til they're going up.
That leads me to another question...
I can avoid one of the crossings all together by taking a road that passes under a viaduct. There's less traffic on that road and no stoplights but the hill after the crossing is extremely steep but not very long. The route that has an at grade rail crossing is still fairly steep but isn't nearly as long with a few stop lights and a lot more traffic.

I have the same dilemma; just over 7 miles, more city driving and 55mph is the highest speed limit or 13 or so miles with more highway driving and a speed limit of 70 mph, drives people nuts when I don't go over 60. :)

I like taking the highway since it brings up my average mpgs but I also like taking the shorter route since it reduces my overall fuel useage for the week.

Does your car get to operating temp on the shorter drive? And by operating temp I mean oil temp, not coolant.
I always like to try and get the oil up to it's normal operating temperature to get rid of any condensation that may have built up while the engine was off. I value mpg but i also value vehicle longevity and engine health.

The non-stop route is better.

Reduced wear on vehicle and components, not to mention the lower accident rate plus severity thereof in using a limited access roadway, offsets the fewer extra miles. Full warm up is more likely. Lower vehicle wear over time saves energy or money.

And time is crucial. Few will have to relinquish a vehicle due to total miles. Most will time-out in regards vehicle reliability.

The heavier the vehicle the more accurate this is. I don't average 100k on tires and brakes by making bad route decisions. Or that the clutch is original at over 200k miles. And besides u-joints, repairs have been limited to pocket change.

A few more miles at a lower rate of consumption with faster warmup and steadier temps plus minimized use of brakes concurrent with minimized acceleration events is a recipe for success.

To keep it simple, keep the average mph high as per engine hours. Give the vehicle what it wants versus forcing it to an unnatural existence. Minimize risks.

I assume so since I can watch the coolant temp gauge fluctuate slightly as the thermostat opens a few times during the 7 mile trip, even at below zero ambient temps. I don't have an oil temp gauge so I don't know for sure.

Usually 15 miles or so is enough to get the oil up to temp. Keeping the engine in good shape is key to good mpg so a good highway run a couple times a week or so is a good thing.

Highway miles are always easier on a vehicle than stop and go. I'd liken to get good mpg and also have a healthy engine and transmission.

Which route takes longer is the question. I will happily use a little more gas if it gets me there 10-15 minutes faster each way.

They're about the same time wise

are you neutral coasting in your auto?

No. The black magic slushbox weirds me out a bit so I leave it in gear for coasts. At higher speeds, I presume when the tc is locked, the engine rpm coincides with the vehicle speed; but when I coast at lower speeds the rpm drops to idle, around 550rpm.
Boy I sure miss having a standard trans.

Weird that yours drops to idle at low speeds. Mine DFCO / engine brakes down to 17 MPH while in gear! Only time RPMs drop to idle is at gear shift points, and even then it's above idle. Only time it really does go into "neutral" while in D is when I release my foot after I floor it (up to 5500 RPMs then foot off and goes to neutral, foot back on it goes into 5th, pretty cool I think). I agree with you on the whole shifting to N in an auto, kinda creeps me out too. I feel like in order to make the tranny last longer, you can't do neutral coasting in an auto.

Fortunately, for us, we can coast longer in gear than if we had a manual tranny. Since we have taller gears we will not be engine braking as hard, and we will also still be in DFCO (I coast from 50 to 35 between my house and the redlight which is about 1/2 a mile using DFCO). I don't know about your car, but the same car I have with the standard trans has significantly shorter 5th gears than in the auto trans.

The dfco is a good reason to keep it in gear while coasting, even if you have to give it a quick shot of gas if you bleed off too much speed. As close to EOC as an auto trans can get! :)