Poor Fuel Economy - Prius Model V

You're in Rochester, MN. I assume it is as cold as a human could imagine there now. And at 1,500 miles your engine is not yet fully broken in. And I wonder what pressure you keep in your tires?

42.8 mpg in the bitter cold of Minnesota is not bad at all. I don't think I can name another mainstream car that will do that well in serious cold.

I'm outside of DC. During the very cold couple of weeks surrounding Christmas, when we got two feet of snow, my mileage was also low 40s. When the roads cleared and it warmed up, I averaged 52 mpg. When I filled up this morning (the beginning of the great mid-east-coast snowstorm), the computer read 51.1.

Don't worry. Your car is normal.

 

MN winters. Hang in there.

Most important factor in local mpg is conservation of momentum. On the highway, its speed. Winter kills mpg, but can be mitigated.

What psi do you run?
Is your grill blocked?
Do you have a garage to park in?
Can you plug in an engine block heater, if you added one?
When you "coast" are you taking your foot off the accelerator? If so, that is bad. Instead, keep enough throttle input to stay out of regen on the HSI. "Glide" instead of "coast."
Accelerate near the top of ECO on the HSI, looking ahead to minimize braking and regen needed.
Even small amounts of snow/slush will kill mpg. Not much one can do there.
Are you having to warm the vehicle to de-ice? Not much one can do there.
Where do you run the climate controls and seat heaters? There is a tradeoff between your comfort and your mpg. Play with that balance.

Good luck.

 

It's been mentioned a million times on this forum, but if you drive short distances, your fuel mileage will generally be worse than driving greater distances. The engine must warm up from a cold start, so it will run and burn gasoline until it reaches operating temperature. Running the heater will require the engine to run more frequently in order to generate heat.

If you drove a Corolla in Rochester, MN in the middle of winter, your mileage would be lousy compared to the mileage you would get driving in the summer.

If you didn't realize this before you bought the Prius, you probably didn't spend enough time on Prius Chat researching. If 39MPG is not enough mileage for you, by all means take the car back and unload it. Just let us know what you get that gets you better mileage in MN in the winter - and still has the ability to haul 5 in relative comfort.

 

I would say the main thing is probably the cold. People are always very disappointed at how the mileage drops when it gets cold. Even I am. I've owned a Prius for almost six years. That lovely warm glow I get when my commute averages in the 50s is the harbinger of spring (and summer).

I would set the tire pressure at 42 psi in front, 40 in back. You could even go higher. I'm keeping my 2010 at 44-42. This will make a very large difference in mileage.

And I'll second what Ibmindless said: short trips are the other big mileage-killer. If you aren't on the road for 10 minutes or more in a typical trip, you're never getting the engine warmed up enough (not just warm--this is true in the heat of summer as well) for it to do its high-mileage thing.

My commute to work is 18 miles one way, through suburbs. I'm on the road about 35 minutes. In warm-weather months I can average 60 mpg on a tank without driving in any particularly special way. In these cold winter months it will go down into the 40s (mpg-wise).

So once again, don't worry. As I used to hear more than one person say back in 2005, when I got my first Prius: first of all, just drive the car. You don't need to do a lot of special stuff to get really great mileage. You just need to understand how it works.

And yeah, 42.8 mpg is phenomenal mileage in the dead of winter.

 

30 is too low. Try 38 front/36 rear, for starters. I forget what toyota placard is, but it is around that. I'm at 44/42, and that helps the glides noticeably versus even 38/36. Ride gets harsher at higher psi, so try a moderate level and work up.

Get some foam pipe insulation at home improvement center, say 1/2" inside diameter. Cut it to length and insert in the lower grill slits. Comes in 4 to 6 ft lengths. Get maybe 2 6' lengths. Remove them as temps rise above 50F in the spring. I've run them with temps in the 90s in other vehicles, but you want to watch your coolant temp with scanguage at that temp. This will speed warmups and retain heat which is crucial in local driving.

You can buy the Toyota engine block heater here at the shop. I have not done this. Tricky to install the first time, so wait on that one. Also, the payback on a 50 EBH is longer than that of $5 of pipe insulation.

Good luck.

 

I don't think it is a good idea to over-inflate the tires. The correct tire pressure is on a label by the door jam. If you open your driver's door and look at where the locking hatch is on the right hand side, it states the correct tire pressure for the size of your tires. For example, my 15" 195/65R/15 Front 35psi, Rear 32 PSI. Over-inflate can lead to slightly better fuel consumption but it will also decrease the contact patch area of the tire to the road. This means decrease in braking distance. Under inflation will soften the ride but due to increase contact patch area, gas consumption will increase too. I'd suggest stick to the factory label. They are there for a reason.

 

Toyota sets its placard for a soft cushy ride, at the expense of fuel economy, handling (hence safety), and tire life. Just like ford did with the explorer.

PSI above placard makes the ride harsher, but improves tire life, handling, and fuel economy. But the OP at least needs to get up to placard.

Tire manufacturers maximum psi is the best for the tire and owner pocketbook.

 

I agree the 2010's FE is disappointing. Block the grill & inflate the tires. I'm not going to argue the merits of tp here as enough threads already have it covered.

I moved cabin temp up to 74F & fan speed up to "2" as this seems to shorten the "warm up" time. Firing up my seat for a bit helps in the comfort dept.

I run in standard mode and can't get the car to deadband.

 

As already mentioned - short trips and cold temperatures kill mpg's....mainly because the ICE is running more often, and for longer periods. Your tire pressure does seem on the low side, but I don't think that's the main problem. IMO, it's the length of your drive, ambient air temperature, terrain and speed you drive at that ultimately determine what mpg's you get. My average coumute speed (30 miles each way) is about 35 mph, on gently rolling/flat terrain...and I routinely get into the low 50 mpg in Maryland's winter temps (typical daytime range from 45F - 25F). In the Summer, over the same commute, I got into the high 50's, with a few tanks into the 60's.

http://www.fueleconomy.gov/FEG/factors.shtml

But rest assured that cold temperatures also kill mpgs on all other cars and not just the Prius. The EPA temp range for it's tests fall between mid-60's to mid-80's. In 2011, new tests will be put in place to look at fuel efficiency at lower temperatures.

[ame="http://en.wikipedia.org/wiki/Fuel_economy_in_automobiles"]Fuel economy in automobiles - Wikipedia, the free encyclopedia[/ame]


Finally, remember the EPA mpg number is really some average number over a year. One should not expect to get the EPA mpg number every day of the year. If you watch your speed and your daily drive is more than 5 miles, and you drive conservatively, I would expect that you will see 50's when temperatures get into the 40's...good luck.

 

JimN, what do you mean by deadband? No arrows? On the HSI, just put the throttle down right above regen, and the ICE will shut off, and the electric piece will be approx. zero, too. I don't trust the new energy screen arrows. Do you have a scanguage? You can watch rpm and amps.

Of course, it won't shut off the ICE while running defrost or seat heaters for the most part.

What are you achieving that is disappointing?

With almost 3000 posts, guessing you own(ed) a GenII before your 2010?

 

I have to say I am baffled by this assertion. Disappointing compared to what?

As you can tell by my signature, I own two Priuses. They have been driven by the same driver under the same conditions, and have both been well-maintained.

It was clear to me after the first month I owned my 2010 Gen III that the average gas mileage per tank was a good 6-8 mpg greater than the Gen II model. That has continued to be the case during the five months I've owned my Gen III.

I wonder what kind of mileage you were expecting?

 

Yes, I had a 2006 and I have a ScanGuage. Over a comparable period last year I had 51.5mpg compared to 48.5mpg.

I was/am expecting a 10-15% increase (58-60) in FE over the Gen2. In a rally I was expecting to be able to post FE numbers close to the biodiesels run by the High School kids. In this car I'd have a hard time keeping up with a noob on soft tires in a Gen2.

The last time I had a sub 50mpg tank was 6/1/09. The next tank was 77.5mpg (for a combined 61.0) so this was a fueling anomoly. 2/10/09's 47.6mpg was the last real sub-50 tank.

I have a 35 mile commute. I run the defrosters as needed. (60mpg doesn't do you any good if you can't see.) I put the heat on around 150F (74F & fan at 2 bars). Seat warmer generally stays on for only a few minutes. (If the ICE is running when stopped at a light I turn off the fan.)

Even when I was carpooling & my trips were cut to ~15 miles the numbers didn't drop.

When I get to the office I like to take the tour through the parking lot. There is an access road zoned 15mph around the lots. Climate control & radio is off.

In the 2006 I'd have a full battery and turn onto our road at 25mph. The goal was to stay all electric and have no arrows on the MFD. I'd be able to stay all electric (unless someone got behind me) and could get no arrows some times.

In the 2010 on the same course the arrows on the MID (Mis-Information Display) switch between charge & discharge. Again, I can stay all electric until someone's behind me.

I display RPM, MPG, GPH & coolant temp.

I know the car's new & different, the 17's aren't as efficient, and winter's rough. At least the FE IS improving over the 4 tanks.

It took a long time to get the 2006's numbers up. I wasn't expecting this much of a learning curve.

 

JimN, if you haven't already, put in the amp xguage (see adrianblack's spreadsheet). That and rpm guage give a clearer picture I think than the MID arrows.

I think whether the 2010 is an improvement depends on how good one was with the Gen2. I never owned a Gen2. It seems to me that the 2010 makes it easier for a newbie to do 'good' but may make it harder for a pro like you to excel. Have you read Wayne Gerdes Gen III review at cleanmpg?

 

From just a guesstimate fuel economy drops between 1/4- 1/3 mpg per one degree fahrenheit below 60 degrees.

Just to relieve your anxiety from seeing low fuel economy numbers.

During the late summer early fall I was averaging low fifties with mostly short trips of 3-4 miles.

With temperatures in the sub twenties over the last few weeks my fuel mileage has dropped into the low to mid thirties.

Yep cold temperatures do hammer your fuel mileage that much.

Thank heavens I wasn't driving my old Volvo I'd be in the 13-15 mpg area.

 

Just my 2 Cents... and this coming from someone who's owned and owns everything from Gen 2 Prius, Honda Hybrids, and a gen 3 Prius in one of the coldest cities in North America:

My tire pressure is always set at or slightly below the maximum tire pressure rating of the tire. The placard tire pressure is the MINIMUM safe pressure anyone should sport in ANY car, and as it has been stated before many many times it is also the best for ride comfort which hapens at the expense of fuel economy and tire longevity.

I have the front grille blocked as demonstrated here and I use a block heater. So far, I been averaging 42 MPG (5.6L/100km) or better in temps of -13F and even lower. My urban commutes are no more than 10 miles long.

In colder weather conditions the 3G Prius is actually better than the 2G which puts it right there in the same league as my HCH-II under the exact same conditions. Also, using anything but the ECO mode borders on heresy of the highest order for me.

Block the grille, air the tires, install and use a block heater and use a scangauge. It is well worth it.

Cheers;

MSantos

 

Rochester? That's basically nothing but extremes, a city island far from the metro area surrounded by open country.

Don't expect MPG like mine, up in the Twin Cities. My 4 tanks this month calculated to 41.7, 47.0, 48.7, 44.9 for an average of 45.6.

MPG for both of us will go up quite a bit when the warm season finally arrives.
.

 

What does a block heater do to increase your MPG's?
Temps here are generally in the low 40's ~ would the block heater do me any good?