Not Complaining, but want to understand better...

Short trips result in gas being burned to heat the engine/exhaust to a point where the engine has minimal pollution.

If you do nothing but short trips then expect MPG in the low 40's.

Once winter comes you will see another few mpg lost to heating the inside of the car.

 

EPA estimate on the Gen II is as follows

48 City
45 Highway

YMMV

What you are posting and seeing is normal. If you want to get superior mileage, learn about hypermiling. There are links in my signature that explains that.

Best of luck to you.

 

You have a variable capacity bladder fuel tank. You cannot accurately calculate mpg by gallons added and miles traveled. We must rely on the trip computer for mph.

 

It seems that the onboard computer is a little over what actual mileage is. Most folks who drive a Prius calculate their overall mileage over several tanks of fuel since one tank will not give accurate figures due to the bladder. You might consider averaging a minimum of five tanks of fuel together to get a good basis of miles per gallon. Fuelly.com is a excellent site that can be used for just that purpose.

 

I am getting about 32 MPG, with a combination of expressway and local driving. What am I doing wrong?

 

Start here. This questionnaire will give us a lot more clues to possibly help, and covers most of the common issues except excess brake drag:
Fuel economy complaints/queries? Please copy, paste & answer these questions, esp. if you're new

 

How old is your 12v battery? What is the voltage reading of your 12v battery after sitting over night? (Method Here)
1 1/2 yr old 12V battery, It usually shows 2-3 bars t start.

Have you had your alignment checked? Any pulling or abnormal tire wear?
Yes - It has been maintained by AutoNation Toyota for the last 5 years.

- Are you using the factory tires and wheels? If not, please indicate tire make, model and size
Yes

- What are your tire pressures?
Factory standard, checked every 2-3 weeks at full service station. Dash warning for tires has never turned on.

- Make, model, year, engine and transmission of previous car? (e.g. 08 Honda Civic Si 2.0L 4 cylinder, manual transmission) What did you actually get on the same trips/commute? (Please give us actual numbers, not EPA ratings.)
2005 Kia Sedona, 14 - 17

- How are you trying to drive (e.g. trying to stay in electric only?) and how hard are you braking?
No and usually coast before braking

- Are you "warming up" the ICE (internal combustion engine) by letting it idle after powering on?
No

- Are you driving using D or B mode?
D

- HVAC settings? Are you using the heater, AC, auto mode, etc.? If using auto, what temp is it set to?
72 autoset

- If reporting a mileage drop, did anything significant change on your car (e.g. accident, hit a curb or big pothole throwing off alignment, oil change/other maintenance/repairs, changed tires or wheels, etc.) or your commute?
No major drop, it has averaged 34-38 for 3 years.

- What fuel economy are you getting and how are you determining fuel economy? (trip computer or manual calculations)
Info screen. Most recent - 178 miles @36.5
mpg- What fuel economy are you expecting and why?
42 seems normal

- What are the approximate outside air temps?
80-92

- How long are your trips?
1 mile, 5 miles, and 30 miles each way.

- How much of it is city vs. highway? Roughly what's the average speed in overall and of each segment? Is there a lot of stop and go driving?
40 - 60 trips of 1-5 miles city driving, and 6-10 round trips 60-70 miles at 75 MP expressway driving

- What region/state are you in? (if you haven't set your location in your profile)
Central Florida Gulf Coast

- What's the terrain like of your drives? (e.g. flat, gentle hills, steep hills, etc.)
flat

- Is your oil overfilled? (i.e. above the full mark on the dipstick)
no

 

Much of my driving is expressway at 70-75 MPH.

 

Here are my initial thoughts. Hopefully several others will chime in too.

Are you sure about the tires? A 2006 should not be on its factory tires anymore. They should have been replaced some years ago for age alone, no matter how few miles are on them. We'd like to know brand and model of what is installed now, lots of tires are not low-rolling-resistance.

How many miles on the odometer?

Are you checking while the tires are morning-cold, or after a highway run? Recommended pressures are for cold, not highway-warmed.

This is worth getting your own pressure gauge, not depending on the unknown condition of a beat-up service station gauge. Many of them become inaccurate from use and abuse, though home gauges are known to be off too.

Also, we like to see you quote actual pressure numbers, not merely say 'Factory standard'. This will catch a few misunderstandings.

But has dropped to 32 now?

Neither of those types will get great MPG.

Those 1 and 5 miles trips on a cold engine and hot passenger cabin will clobber mpg in any car (except non-plugins), and there is little you can do about it. The 1s are particularly bad, because you have to (partially at least) warm the engine and cool much of the cabin, using a good bit of fuel without driving any real distance. This drags down the average.

For the 75 MPH trips, take a look at this Gen3 chart, then subtract 5-ish mpg for being a less efficient Gen2, then subtract several more for your heavy AC use. Though that still ought to produce around 40, better than you are getting now.
Updated MPG vs MPH chart | PriusChat

It would be useful to learn what you get on a highway trip alone, without any of the short trips mixed in. Reset the Trip gauge when you start one of these trips, and tell us the resulting figure when you get back home.

----

Additionally, do your wheel hubs get hot? This could indicate excessive brake drag.

Resetting the Trip gauge before some of those short segments will also be instructive, highlighting the cold start (and hot cabin) penalty. The MPG should always start out horribly low, then climb the farther you drive. At 1 mile, it will still be horrid. By 5 miles, it ought to be climbing to a semi-decent number, but still not getting close to what the car can really do.

 

Thank you for the advice. I had not realized the lower speeds made such a difference. I had been driving at the flow of traffic speed, 75-80 MPH, during my freeway driving. I have reduced it, moved to the left lane, and hold it down.
I am now getting 42 MPG, with the A/C on all the time. ;-)

 

For trips 30 miles or less, going that extra 5 -10 mph does not really get you there that much quicker.

Verses 60 mph, you'll get there 2 min19 secs earlier at 65 mph; and you'll get there 4 min 18 secs at 70 mph.

On longer trips you will save more (obviously), but remember, even if you try and maintain 80 mph, your average will more likely be around 72 mph, depending on circumstance.


Just adding what I think is an interesting data point.

 

I hope that was a typo and you actually moved to the right lane.

I agree with the tips and info above. Slow down, anticipate stops (this make a bigger difference that I think most people know about), and combine trips as much as you can.

The ultimate solution if you make lots of short trips but still need to make long road trips would be a plug in like the PiP or Prime. I've put about 11,000 miles on the Prime since I got it in March and that includes a 6,013 mile road trip to AZ, NM, CO, WY, and other places. My total cost for gas & electricity is $437 which is $641 less than the cost of just gas at 28 mpg. That's mostly because my short trips use no gas at all and electricity is way cheaper than gas.

 

How old is your 12v battery? What is the voltage reading of your 12v battery after sitting over night? (Method Here)
1 1/2 yr old 12V battery, It usually shows 2-3 bars t start.

The bar indicator is for your "big" high voltage hybrid battery, not the 12v battery. If your display is showing 2 purple bars in the morning, be aware you are likely looking at HV battery failure in the near future.

A weak HV battery is also a MPG killer, as it requires the engine to run more often.

 

... Right lane, I hope.

Don't slow down more than is safe for the prevailing traffic. Safety is more important than MPG, so going with or close to the flow has its benefits. Just don't be among the numerous folks pushing for a faster flow.

 

Wow that's surprising. Are you driving at 85MPH or above in right most lane. If you are used to doing that than you are driving the wrong car.
I used to do 80MPH Highways in Gen II 2005 Prius and it noticed it suffered a lot , but it still got above 40 MPG in Highways. Here's what I found out , the sweet spot highway mileage for Gen 2 1.5 L Prius is actually is at 55MPH. I noticed it when I drove 5 miles at highway traffic lane where max speed is 50MPH. I noticed I got around 65MPG, and when I got back to 70MPH it went down to below 50MPG. Nowadays I try taking dual carriageways for longer trips whenever possible to maximise efficiency. Maybe for the GenIII or above Priuses with larger 1.8L , the sweet spot can be pushed further upto 65MPH. But I suspect it's still not the 70MPH.

But I am kind of optimistic that the new Corolla Hybrid with the same 1.8 L engine but lighter in weight than Prius , the engine can push the sweet spot to the UK standard motorway 70MPH. It could be the king of mileage combined city and highway in the UK.

Posted via the PriusChat mobile app.

 

I had a 2013 Gen 3 Prius, which had a lot of daily short trips...with longer road trips on weekends.
And I'm going to say, I always got higher MPG on the highway, as opposed to the city.

I never perceived it as a problem. I attributed it to my City driving mostly being shorter trips.

I just calculated my overall MPG by a months or full tank yardstick. But if I was paying attention, my higher gas mileage always came on the long road trips on the weekends which usually included long freeway stretches.