My 1st 500+ tank

Despite getting between 50-55 mpg on most tanks, we've only broken 500 miles once, 522 to be exact on a 55.1 mpg calculated tank. The infernal bladder and digital gauge make it tough to do much better than 450 miles consistently at the flashing pip. A sub-9 gallon effective tank and incredibly uninformative fuel gauge are handicaps.

 

My last tank was 809, :rockon: but I cheated with extra electrons coupled with a 10.8 gallon fillup.

So I guess a more informative posting would be to include both the mileage and the amount required to fill the tank.

 

I just did my first +500 miles tank last weekend. The light flashed and a message popped up at 539 miles, I was on the highway and had to travel another 8 miles to get gas. I was a little nervous with the damn pip flashing but others have posted they have gone 30 or more miles with a flashing pip. The filluip also was a personal high, 9.1 gallons or 60.1 mpg

Kirk

 

I'm thinking of buying Prius now for business, I have to drive a lot, mostly highway from 20-30mi, to 100-150 miles one way. I'm usually driving at 75-80mph, and I heard highway miles are usually lower than city on Prius.
What MPG should i expect?

Thanks in advance.

 

What was wrong with the first '06?

 

Low to mid-40s MPG. 75 mph should be 44-46 mpg, 80 mpg should be 42-44 mpg, depending on weather, traffic, etc. 40 mpg minimum at those speeds.

 

GenII Prius, 84 degrees F, constant highway speeds of 65-70mph, 35 miles in each direction, with 2 *very* full grown adults, and a small amount of "in town" driving while I was in town.

I averaged 52mpg during that trip, last week.

And, since I just got my Prius, I don't know all the "tricks" yet...I'm not some super-hyper-miler, yet.

Chuck

 

going from san diego to orange county I get around 52 going 70 mph or so. very satisfied, great car for a lot of driving, but you could probably expect somewhere in 40s or low 50s.

 

Assuming he is asking about a GenII and not the newer model, at 75-80 he will definitely not be in the low 50's mpg wise. I've been able to get 51-52 mpg at 72 mph cruise for extended trips, but not if there was any crosswind or cold weather. On one of these trips I watched my mileage drop by 5 mpg over 150 miles when a strong crosswind developed. The rule of thumb is 60 mpg @ 60 mph indicated, and subtract a mpg for every mph above that. Folks can do a little better or a little worse, but this is in the ballpark for normal driving.

 

This was also my rule of thumb target for most of the summer and early fall, but most of the time some complicating factor knocked me a few points lower.

Winter has arrived, and I don't yet have a rule of thumb for this season.

 

I agree. At 65 I get upper 40's, maybe 50 mpg. At 77 I was getting 40 mpg. My experience is that there is a major mpg cliff once you get over 70. I tested this on a recent highway trip and went from 49 mpg at 70 to 40 mpg at 77. That's a 10% pickup in speed but a 18% decrease in mpg. The faster you go above that the worse it gets.

Now one thing to remember is I believe this same cliff exists in other cars/trucks.

Kirk

 

Can someone explain the "effective 9 gallon tank" thing to me? Is it the same on the 2010 model? My manual says 11.9 gallons US.

 

My first tank ever with my new/used 05 was 505 miles. I haven't come too close to that since, but what a way to start out!

 

I'm not sure about the 2010, but my 2008 (gen2) has a fuel bladder, which makes the capacity vary - a lot in my case - and 11.9 gallons is the (theoretical) maximum capacity. I have never gotten more than a little over 8 gallons in a fill-up. Of course I nearly always fill at 2 bars, but even the one time it had just reached the last flashing bar, I still got less than 8.5 gallons. I've had so much trouble with the pump shutting off early that I'm satisfied to get over 7 gallons in a fill-up.

Unless I start getting some spectacular MPG's, alas, I'll probably never see a 500 mile tank.

 

In very few makes of auto can you use the full capacity of the tank. Typically one might get 90-95% once accustomed to the nature of the tank. But in a GenII Prius it is much more difficult to get anywhere close to that high of a percentage. There are two major reasons: the bladder/vent system, and the "guess" gauge.

With the North American GenII the fuel bladder really complicates things. Shrinkage alone in winter can reduce 10-15% of the capacity--resins have greater expansion coefficients. The vent system can make whatever capacity there is hard to use as well. I had one fill which was nearly 3 gallons short...on what should have been a 5+ gallon fill and instead was 2.5 gallons. This was a 5 pip fill and the last one of those I intend to do.

The digital gauge really sucks because it won't even display anything below 1/8th tank. Once you get the flashing pip at 12.5% you are running blind. It also won't show you the small incremental changes throughout the range, including the top of the tank.

The result of all of this is that for most of us the effective capacity of the tank is somewhere around 9 gallons. That is what I usually get between full (stopping the fill after the first shut off) and within about 10 miles after the flashing pip. For me this has resulted in fills from 8.2 to 10.0 gallons so far with ~9 gallons being the norm.

While the 2010 does not have the bladder, it does appear to share some quirkiness in filling because of the closed vent system--but to a lesser degree. (I've gathered this from listening to new owner's reports.) Simply put, such systems are prone to problems from flashing fuel, liquid seal legs, and two phase flow. These can result in premature shut offs of the gas pump and difficulting getting it to fill.

 

Question.

With this flux in the capacity of the tank and the digital gauge not being that accurate, is there some "mod" that can be done to give you more accurate readings of the tank capacity/amount of fuel left, etc?

The ScanGauge II seems to be something along those lines, however it also seems to lack that information which would be incredibly useful. Anyone have any ideas/ thoughts on this?

Just wondering (Im a recently new owner of my '07 (GenII) Prius.

 

very good grass-hahpa (as they used to say on the ol' Kun Fu TV series) . . . . your journey truly begins after you learn to snatch the bean from the palm of my hand






put another, way ... take it from me, the mpg thingie can REALLY get obsessive
"... must ... get ... 800 ! ! ...