Abysmal city driving fuel economy

Try taking a city excursion for at least a half hour, driving no faster than 45-50MPH. Then you'll understand the car better. Your actual city is about what you'll get for the first 5 minutes, which is all you let it drive. After that, MPG spikes up, unless you used the AC to cool and the ICE has to charge the HV battery back up.

 

short trips of only 5 miles will put you right about where your at. Sorry this car isn't an Insight. Plain and simple. I'd say your probably getting about all that the car will deliver with insufficient warm up time. Plus your ICE is 50% bigger along with a car that is bigger as well.

 

Let your car warm up, after the first 10 minutes in the city I consistently average over 60 miles per gallon.

 

Think about what you would get in a Toyota Corolla! The Insite has the advantage of low weight and 2 passengers etc. The Prius does many things the Insite does not. You have some advantages over others. Temperature is a great advantage. Can you imagine driving 5 miles in North Dakota at a time in winter!! You have at least that advantage, I on the other had could drive to North Dakota in winter if I wish, or not.

 

The first 5 minutes, the ICE is running longer and less efficiently to warm itself and the catalytic converter up. Besides, until the catalytic and O2 sensor are warmed up, the ICE will run in open loop mode, using a guess to how much fuel to mix with air for complete burn.

EPA drive for city is longer than 5 minutes, that's why their figures are higher than yours. You are not driving the same way the EPA did. Also, are you using the AC? EPA doesn't. The AC is much more efficient than a conventional one, but if your cabin is really hot during startup, then the AC will run full blast to cool it down. That will take alot of energy initially.

The reason EPA city is higher than EPA highway is lack of waste that normally kills a city EPA. ICE doesn't run at traffic stops (unless still in early stage of warmup). Also not only does ICE stop when not using it to propel the car, during braking, it is actually RECOVERING energy, rather than wasting the momentum as heat from the brake friction. For highway EPA, the test speeds are slow enough to just about be at a typical car's sweet spot, which is about 45 MPH. About when the transmission just shifts into its last gear and locks its torque converter. The highway test on a conventional car has no stops to waste gas, so all of it goes towards best MPG. for the Prius, the highway test is not at the most efficient speed. Since it has no 'shifting', the best speed is much lower than the test.

You will really have to research and understand the car, and how EPA does its testing.

 

If it's possible for you to take your short trips close to one another, that will help - the Prius does a good job of staying warmed up, so you'll get better mileage with three five-mile trips in 90 minutes than you will with the same trips spread over 8 hours.

Despite the EPA figures, many Prius owners - possibly most (hmm, time for a new poll?) - get better mileage on the highway than in town. The mpg-killers are short trips, heavy congestion (which minimizes opportunites to coast or brake slowly, and sometimes requires rapid acceleration), lots of full stops, and cold weather (obviously not a problem in Honolulu!). The first three of these conditions are more likely to occur in town than on the highway, hence the decrease from optimal mileage. If you take DanMan's suggested trip, you may come close to the EPA figures.

Thanks for the specific information, btw - it's a huge improvement over the usual "I'm getting 40 mpg, is that normal?"

 

Glad it's not just me. I almost started a post like this myself.

I'm getting 36 mpg in the city (mostly 7 minute trips to work or the store).

At first I thought that I must be a lead-foot. But I am very slow to get up to speed (and yet I still leave some people in the dust... where'd they learn to drive?! 0-60 in 20 minutes?!).

I have had the A/C on almost all the time so I expect a hit because of that.

 

Yep, Short Trips kill the gas mileage. I know I do a lot of them too.

The EPA uses a warmed up car and drives continuously for I believe 30 minutes, stop and go city style driving, on a treadmill type thing. In other words, not in a real city but in a lab.

We use a cold start, run around a little, then stop the car. It cools down, then we "cold" start again. It is warmer and we will get better gas mileage, but not the EPA numbers.

My last car was a 1993 Ford Escort Wagon. Basically the same size as the Prius. I got 25 mpg overall, about 20 on my short runs. In the Prius, I get 35-40 on the short runs, and 45 over all. It's at least a closer reference than your Insight. Me? I needed a Mom car, the Insight was never an option.

Lisa

 

If you do a search here on PC on the 4 stages of hybrid operation you will get a better understanding of the Prius ICE operation. It isn't very efficient till the O2 sensors are at full operating temp, these along with the ICE temp, speed and time help determine when the car goes into S4, full hybrid operation. The critical temp is the ICE has to get to 70C before it will allow S4. By the time it gets to 70C the cat's and the O2 system it at normal operating temp. This normally takes about 2 1/2 -3 miles at normal street speed. Slightly less if the OAT is above about 75-80F. But the 4 stage is where the fuel economy starts to really climb. Tire pressure just like in the Insight is critical and driving style. Anticipating lights and such, which your probably familiar with driving an Insight. Like Coloradospringsprius said stack your trips to keep the ICE warm will probably be the trick you can use to get the best mileage possible.

 

I have a short ride to work. About 10 minutes. Never over 35 mph. I was disappointed with mileage when I first got the car. I couldn't get over 40 mpg on my daily commute. After 20,000 miles, I have the following suggestions:

Your mileage will improve with time even if you do nothing to help it.

To help get better mileage:

1. Switch to 5-W30 synthetic oil.
2. Put as much air in the tires as you are comfortable with. Keep the 2 lb front/rear differential and don't exceed the tire max.
3. At first start allow the ICE to run and warm up and stop before driving away. This happens for me getting the car out of the garage.
4. Drive "normally" for the first 5 minutes. ICE runs a lot. Usually see around 25 mpg on the first bar.
5. Pulse drive after ICE is warm. Second 5 minute bar usually around 75 mpg.

Result is I keep an average over 50 mpg on frequent 10 minute drives.

 

I thought I'd have the worst MPG since most of my trips are less than 5 minutes. At 45+ MPG, I'm pretty impressed. I've only used about 4 tanks and one was a 500+ trip. All in warmish weather, so i may not be a good data point..

 

The EPA definition of "city" is actually much more like "suburb" type driving... which is absolutely fantastic for Prius.

Most of my current tank has been "suburb", and at 287 miles the Multi-Display stated a very pleasing 55.7 MPG.

Regardless of that, no non-hybrid car of Prius size & weight can claim a MPG of mid-30's in "city". Most would consider themselves lucky to get 20 MPG under those same conditions. And they aren't anywhere near as clean as Prius.

 

Please DON'T idle the car to warm it up before driving it! The instantaneous fuel consumption numbers you get while actually moving will be better, but they will be more than offset by the 0 MPG you get while not moving and you will use more gas in total.

The fastest and most fuel efficient way to warm up any car is to drive it, gently for the first few minutes. As others have pointed out the Prius' engine will run for a little while in any case to warm itself up, so you might as well get some useful work out of it while it does.

 

I'm surprised nobody has mentioned keeping the A/C on "LO" setting. At this setting, the A/C runs entirely off the battery without the ICE. Set the A/C any higher and the ICE turns on. So when you do use the A/C, make sure it stays on "LO" and that will help immensely.

And don't use the window defoggers unless you have to...they, also, require the ICE to run. Better to coat your windows with something that will prevent them fogging up.

 

The MFD numbers are generally 2-5 mpg higher than actual for me. My city is usually pretty bad also (25 mpg), but my highway is better than 51 (usually 67-99) so I end up averaging about 54 mpg for hand calculations. My wife averages about 48 but she drives like a maniac. We have about 25-30 min commutes. My wife also tends to do more city driving (errands) where as I just drive to work and drive home.

We do have significant winds here (35-60 mph) in all directions. I drive 60 mph on the freeway (in city limit) and about 35 mph in city. The constant stop signs and lights kill my mileage. It would be worse but I usually anticipate the stops and coast. I have also learned how to efficiently take advantage of the hills to accelerate. I have found rapid acceleration is best. Get to your cruise speed as soon as possible (but not flooring the accelerator).

Now that heat has jumped to 105 deg I have been using the A/C constantly but only on the 1st or 2nd setting. I have not noticed a change in fuel economy (not sure if the dynamat extreme and huber optik is the reason ffor this or not).

 

My tank was at 48.1 mpg, then I started going to Duke and back again on a daily basis. The trip is a whopping 3 miles and in 3 days (it IS Wednesday, right? I'm disoriented) it has dropped my average to 47.7. Looks like this tank won't hit 48 average, I only have 1 bar left..

My first-5-minutes bar is usually around 40 MPG- that's accelerating to 55 mph, then "gliding" at 45 mph. Temps here are warm but I open the window and don't use AC. In the AM it's usually not too hot anyway.

This is normal. Short trips and lots of stop-and-go will drop your average.

Read about hybrid operation a bit and you'll see why the highway is lower than city. Summarized, it's because the ICE has to be running at high speeds while in city driving the car can usually run on electric.

 

Opening the window does add to the drag coefficient which affects the mpg as much as the A/C does in ICE only cars, but at 60 mph...I'm not sure what the difference is at 45.