calculated vs. computer MPG - Please post your results

Typically the dash mpg will be 3 or so mpg higher than actual on my 2010 Prius II. Example - dash shows 64.0 mpg - actual calculates out to 61 or thereabouts. Not a big deal - it's still relative - the higher the number gets the better mileage I'm getting.

 

Just filled up for the first time and I'm a bit disappointed, but I'm assuming the dealer really gave me a full tank when the car was delivered.
The computer said I got 48.0 mpg. My calculations at the pump put me at
44.30 mpg. I guess I'm going to have to wait until the next fill up to be more certain of what I got.
I'm really seeing that it's harder to maintain the MPG's when the temps. drop. My Prius is much happier after warm up. And it's tough to maintain good mpg when I only have a 7 mile commute.

 

Ok, early first refill, couldn't wait 4 pips left ..

Note - First fill from dealer, will take a few refills to get better comparison

model: 2011 Prius Three no nav, no modifications
Odometer miles: 360
date: Dec. 3, 2011
miles driven: 329.7
gallons to refill: 6.244 gal. (87 pump octane Shell brand)
Calculated: 52.8 MPG
Cons gage at fillup: 55.2 MPG
Avg speed: missed exact, but about 28 MPH
tires/wheels: stock 15"
tire brand: Goodyear Assurance OEM
tire pressure: 36 psi front / 34 rear
No A/C, no heater, high 40s to mid 60 F outside temps, mostly dry
No hypermiling, SF Bay Area, near sea level,
Quite a few 10 minute or less drives

Time to get Fuelly.com going

 

How's the tire pressure? I use a little $9 Slime brand gage, works good and a $50 1 gallon air compressor from WalMart to top up. Maybe you have that too?
Maybe it can do better even with the 7 mile commute. Used to have 5 miles each way with '09 Prius and it did about 45 actual in Winter (well, that's Bay Area Winter where it rarely gets to 32 F

 

I haven't checked the tire pressures but I do have a gauge and a compressor so I will check. What's the ideal pressure to be at? I am running stock Yokohama tires.

 

It's really all over the place, I keep mine at 55lbs, some even use 70lbs. a good recommendation is bead pressure, that is the pressure stated on the side of the tire, usually 38-40lbs. If you want a really low life on the OEM tires, use the recommended tire pressures on the left door opening. It is reallly about mileage and handling. If you think the car handles good then that is a safe pressure, with ABS and Stability control, handling does not seem to be a issue any more. As far as smooth ride goes, when the road is rough, the ride is rough. When the road is smooth, the ride is smooth! IMHO. Incidently, just came back from Germany, and overall the roads are incredibly good. Puts our road surfaces to shame!

 

Wow, let me in on your secrets, some of you are getting upper 50's or even 60 mpg, the best I'm getting in 1300 miles is 47. How do you do that? Would love to see 60mpg. I know weather temp has alot to do with it and now it's cold but even when summer arrives, I dought I'll see upper 50's. I drive in eco mode all the time, mostly highway@70mph and use regular gas with 10% ethanol.

 

See "Battery drained in Morning" Post 10, ( my last post ). :rockon:

 

Just fueled up for only the second time in my new Prius. The weather is getting colder in the morning and I definitely notice a difference to the negative because of it. However I am learning to drive it more economically so I did have an increase in mpg this time around. Also, I must admit that I don't think the dealer gave me a full tank on delivery. Soooooooooooo:
413.4 miles divided by 9.216 gals. = a still puny but improved 44.9 avg.
If I can get into the 45.0 - 46.0 range for the Winter I'll consider that acceptable.

 

Sometimes, things are in your control (how you drive) and other things are outside your control (your commute length). If you follow the tips below, you will improve your MPG's. However, if you have a short commute or several short commutes, you won't see the great MPG's like others get. The best you can do is maximize your efficiency for your commute.

Are you SURE you want to hear this?

1. Slow down. Decrease your speed from 70 mph to 60 mph. Yes, I realize that you will be passed by everyone and their dog, but top speed is a mileage killer on the freeways. 60 mph isn't bad (try 55 mph for real emasculating fun) and you'll find that as you cruise 60 mph in the far right lane that you will be much more relaxed driving. Never worry about a speeding ticket again.....

2. Don't tailgate. Most drivers (like 99% of them) tailgate. You should have the ridiculous distances of 2 to 3 seconds between you and the car in front of you. If you are driving 60 mph in the slow lane, it is easy not to tailgate because everyone else is driving faster. If you give yourself distance, you can see what traffic is doing waaaay far ahead of you (1/4 to 1/2 mile ahead). If you see brake lights (bottle neck) you have time to coast or glide up to the slowed/stopped cars. The less you use your brakes the better. You needed gasoline to get you up to speed and using brakes means that energy was wasted. At least we have regen brakes, so we recapture some of that energy, but most of it is lost.

3. Pump up the tires. Try the max PSI in the front and Max - 2PSI in the rears. For my Yokohama Avids (OEM tires) I run 44 PSI in the front and 42 PSI in the rear. Ride is fine for my tastes.

4. Do a partial grill block of the lower grill. NOTE: It would be BEST to have something like a scangauge to monitor your water temperatures. They are on sale at Amazon for under $120, as a bonus, they can read and clear error codes on any car 1996 or newer. You block the lower grill on a Gen III (2010 and later) so to keep cool air going to the inverter. The grill block will keep the engine bay warmer, thus your engine will run more efficiently. It will also warm up faster than unblocked (because you won't have cool air cooling it down). It also means that there will be extra warmth to share with the cabin.

5. Adjust your heater settings in the winter. If you are taking warm air from the engine bay and placing in the cabin, the engine has to work a little longer to get up to peak operating temperatures. It does this by burning gasoline which lowers MPG's. If you can lower the cabin temp by a few degrees, that will help (modestly).

Good luck!

 

Codyroo wrote the short version...
Here is the long one...

Tips & tricks for the “normal” driver to achieve satisfying fuel efficiency on the Prius Gen 3

 

OK. I'm game. I've been keeping pretty good records. Just passed 30K miles. 2010 gen III, purchased 2 yrs ago, no mods, stock tires 50psi front, 45 rear.
Lifetime actual mileage (gas pumps vs ODO): 54.49
Average MPG from dashboard: 58.1
This gives an average error of 6.6% (varies by tankful from 3.5% to 8.7% - this would be due in part to uneven fill).
I generally average ~5mpg better in the Summer (90 F) than Winter (60 F).
When brag I usually use the dashboard number

Driving profile -
1) Daily commute 44 mi round trip 26 of which if freeway @55 mph (slower uphill, glide down), several small hills, southern California - I can almost always get a round trip dashboard reading over 60mpg, max 70.1 on one VERY hot day (112 F). Total to date ~22K mi.
2) Weekend trips - more hills, bikes on back kill aero, wife gets impatient if I go 55, so we go 65 - kills any aspiration as a hypermiler, but not grounds for divorce.

 

Not enough fillups yet, but I'm seeing about 4 to 5% lower actual than indicated. Mild bummer.

 

Your lifetime average of 4.3L/100km is great! :cheer2:
I wish I could get it as well, but roads and traffic here do not really allow it (as well as highway speeds...)...
Your observations about average error are exactly the same as mine, as well as its variance. The seasonal difference is also very similar to mine.

Which means that the cars are the same everywhere, although Toyota handles them differently in different markets (e.g. see TSBs issued there, but not here, etc.). Moreover, that gas stations steal in the same way here and there...

 

I recently joined PRIUSCHAT b/c of all the great info.on here, and this thread is just as helpful. I recently got my 2011 Prius and noticed that in the few fill-ups I've had my calculated mileage has never been as good as the on-board computer says it is. I'm averaging 2 mpg less than Toyota keeps telling me and, like others, have seen that the discrepancy gets worse as the mpg increases. Toyota should update the software...

 

Makes sense, and the discrepancy doesn't bother me too much as long as I have some sense of what it is (and that I'm not the only one experiencing it!). I also learned (nearly the hard way) that the estimated "miles to travel before re-fueling" is a bit less than accurate, too--the EV mode saved the day, and saved me a long walk down a dark road to a gas station!

 

About 5% on avg....see the spreadsheet link in my signature.