MPG trials with different parameters

Nice scientific approach. Yes it would be good to go back to stock for a baseline.

I probably would have done something methodical like you did but I was happy with the results right off. I just aired up the tires to 44psi and the first full tank was 61.8mpg actual (65mpg on the display) and the next 7 summer tanks were even higher (several at 65mpg actual). Then colder weather and winter RFG hit and I'm struggling in the high 50's. Somewhere in there I took off the ugly plastic wheel covers and added a Scangauge, but that's it.

I probably drive slower than you do, which is a big factor. 15" wheels and higher tire pressures probably help, and those higher numbers are from the summer. I can't figure out how to pulse and glide, so I don't. Around town I stick to the speed limits and try to run electric as much as I can, especially if no one is behind me. I try to be aware of traffic behind me, but if someone wants to go 45 in a 25 I'm not going to go 45 just to keep them happy!

 

Nine, please complete your testing then go back to the 15" wheels with high pressure and let us know how it goes. This will help rule out the driving skill variable. As you put down more miles you learn how to drive the car more efficiently. I never used to be able to get 50mpg for the first year I owned the car but later I was able to eclipse 50mpg on a regular basis with no other changes.

Depending on your average speed I bet you could get 50mpg in the summer even with your 18's. It may take some practice. Also keep in mind that gliding is much easier with LRR 15" tires so hypermiling techniques can increase your max mpg difference between the 15s and 18s. If you never try to glide or coast the. The mpg difference between the 2 tires sizes is smaller.

 

I just finished the first tank in my 2011 II with all base features. It looks like I got about 48.75 mpg (calculated, not the display). My morning mileage is much worse than afternoon, I'm in florida but its still in the 40's and 50's in the morning and I seem to use a lot more gas when the engine is cold (car doesn't fit in garage yet). I'm in the 2nd tank now and I'm tracking the mileage a little closer and more of the miles are on the highway. Looks like I'm getting (on the display) about 47/48 mpg, so probably 4-5 less than that if my car holds to what a lot of folks are saying (up to 5 miles off the display for real mileage).

I'm interested in seeing what happens if I up the pressure in the tires (I'm at whatever the dealer had them at).

Since you guys seem to know a lot about the wheels / tires, do you use nitrogen in the tires? The dealer wanted to charge me like $100 for it, but I can get it put in for free next time I visit the dealer my family works for. Have you noticed much of a gain from it?

 

My HSD usually reads about 5% high, so that would be 2.5mpg at 50mpg.

You'll probably see a few mpg improvement. What you'll also get: longer tire life, quicker steering, braking probably about the same. If you drive sporty you may or may not notice less grip, and you may or may not notice a bumpier ride.
Probably wise to raise the pressure a few mpg at a time and see how you like it, rather than go up a lot all at once.

I never bother. Air is 78% nitrogen, so all you're doing is removing (if they flush and refill several times) the other gases. I try to use dry air, which means air from a pump or compressor at home rather than one at a gas station.

 

I also use the 78% nitrogen blend.

 

LOL.
I'm 60 and that's the first time I've ever seen that phrase used.
Will the car go on a diet or will the garage grow?

 

Perhaps a lower viscosity external lubricant?

 

Funny

No the garage needs to lose some weight after the holiday re-org. I've still got the Christmas decoration boxes and the remains of all of the "why the hell is this in the garage?" stuff after I put up the new garage shelves all sitting in the middle of the floor.

 

Nine, what was your "unadjusted" tire pressure? You may be pleasantly surprised when you go back to stock wheels and near maximum rated tire pressure.

Where in Texas are you?
Here in central Ark., I find that the two biggest things that change my gas milage are temperature and wind. Maybe wind even more than temperature.
You are being more scientific about it than I've been.

 

One other thought too, have you checked how accurate your odometer is with a GPS unit? I checked my 07 Corolla last week & while the speedometer is almost perfect, the odometer was recording 4% fewer miles then my Garmin GPS. I'm not sure what is going on with this but it was just a thought.

Has anyone else done this too? And BTW, my Prius fits in my garage too! :lol:

 

I've always done calculated numbers too but then I found that my odometer was showing me fewer miles then I was actually going which ended up giving me a lower mpg figure then I was actually traveling, even though it was calculated.

 

Never been down there. The furthest south we've been on the Texas coast is the Aransas Nat'l Wildlife Refuge, where we were lucky enough to see a few of the elusive whooping cranes.


On the issue of odometers--my odometer seems to be pretty good when used against measured miles on interstates. (This in contrast to some of my previous cars which seemed to register a few percent high--an extra tenth or two over five miles)

I'm surprised at odometers reading low--given the consumer pressure against rolled back or otherwise dishonest odometers.
I wonder what could be causing it? Tire size, inflation, wear (or lack of it) ???????

 

On my 07 Corolla it was. I went 100 miles on my odometer but my GPS showed that I went 104 miles. I haven't checked my Prius yet.