Last bar blinking, how long before I should fill up?

I've only filled three times but here's what I did with each:

1st: last bar flash @ 402 miles; filled at 407 mi.; pumped 7.93 gallons
2nd: last bar flash @ 390; filled at 435 mi.; pumped 10.5 gal.
3rd: last bar flash @ 534; filled at 553 mi.; pumped 10.6 gal.

I really don't know how much is left in the tank when the bar flashes, but I think I'm willing to go as far as the average display mileage for the current tank times the number of gallons I pumped last.

Tideland AM - Colorado

 

With 3500 miles on my '04 it is still not clear how much fuel is actually in the tank at any given moment. I have yet to get over 400 miles before the last bar starts flashing and so far I have not taken any chances. My mileage has been pretty consistent around 50-51 (actual rather than on board display). My tank to tank mileage varies depending on how much fuel the stupid thing allowed me to squeeze in, but keeping track of the overall average using my Palm and a little databas that updates the cumulative mpg automatically, I know that I am doing around 50-51. It's the gallons in the tank that is the unknown.

 

Only two tanks so far and I'm really confused about how the fuel gage actually works. When full with all 10 bars lit, I can go about 100 miles before the first bar burns out. When 9 bars go out and only 1 remains, I can't pump more than 7 gallons into the tank. The tank capacity is about 12 gallons, so is it intentional that the last bar should be flashing a low fuel warning with 40% of the tank capacity remaining?

 

I've driven as far as 57 miles after the last bar starts blinking.

 

With my most recent tank, I drove 65 miles beyond when the last bar started flashing. This was my first 600 mile tank with a mpg average of 56. I got 95 miles to the first bar on the gauge and 311 to the halfway point at 5 bars.

Tideland AM - Colorado

 

Hi: More aviation comparisons here that might help explain things about fuel supplies. At my flight school, we have a model of airplane, brand new, in which the fuel guages read "empty" when there is still about 6 gallons useable fuel in each tank. In other words, the fuel monitoring has a built in safety reserve. It makes it hard to figure out how much gas is in the tank when checking the airplane before flight, and for that reason the manufacturer includes this little siphon tube that looks like a barometer that you stick into the tank; a small amount of fuel flows into a graduated tube which you connect to a little tab on the wing and you read the capacity of the tank from the graduated marks on the tube. Unhandy for the Prius, but it works for the airplane. Toyota has adopted a similar concept. For those used to driving down to the " E" and coasting in on fumes, this kind of system is unhandy.
Previous posts in this column address the bladder expansion issue, and that makes sense to me. I can understand why Toyota has the guage read empty with gas still in the tank because the electric motor's battery needs to be charged up by the ICE, and there wouldn't be any gas to do that if people continued driving down to the big "E".
I got down to the last square on the guage, but it was not blinking. I put in 6.6 gallons of gas for a mileage average of 42. Less than Ihoped for, but I think Humu is still getting broken in. Only have 545 miles on it.
If the "gradually expanding as it wears" theory about the bladder is correct, there is probably not much gas left in the tank when the last square is showing, contrary to my techno babble aviation analogy. I guess we all start out with 6-8 gallon tanks and gradually they expand into 10-12 gallon tanks.
Bob

 

Wow, this thing really is alive! ...It's bladder grows as it gets older.

I just hope it doesn't get a trucker's bladder.

 

My bladder is getting smaller as I get older. Maybe my Prius and I will meet somewhere on the way.

 

On my last tank, the last bar started flashing at 425 miles. I filled at 470 miles, I put in 9.28 gallons. (About 50.5 mpg, which is what the screen said.) I have around 3200 miles on my car, and I think it does get better with age.

 

Wow, I really am happy for you guys that manage to get over 10 gallons in the tank! And the ones getting over 50 mpg.....wow...extremely jealous!!! The very most I've been able to get into my tank is 8.2 gallons after going about 15 miles beyond the last flashing bar. The typical is about 7.5 gallons. I just don't like topping off because the pump shuts off immediately and I've only been able to about .25 gal after three top off passes. And I definitly don't want an overflow. Maybe I'll try pushing it to 50-70 miles after the last bar flashes and we'll see how that goes.

And my overall mpg average after about 3000 miles is an embarassing 47.2 mpg. The very best came on a trip to Vegas at 49.7 mpg. Although the weather is warmer here in San Diego (I never use the AC though) than most areas, the traffic and constant hills are a real killer. And I counted over nineteen lights on my 11 mile commute. I spent over 15 min the other night going no faster than 5 mph.

 

I too am only getting in the 40's as far as mileage in the San Diego area, people here are very impatient so there is a lot of pressure to give it gas when someone is behind you. :guns:

 

Well I've been trying the EV button out. It can really work against you around here unless you know for sure you're going to have an opportunity to re-charge with a nice downhill. I've started to only use it sparingly because I've seen a slight drop in mpg because of over use. Now I use it mostly when nearly fully charged, to prevent an annoying engine start-up when I know for sure I'll be stopping soon, at the start of my commute, etc. It's amazing how quickly the battery SOC can go from green to pink!

I weigh 142 lbs. My briefcase is another couple of lbs I guess, but that's it. I'm currently running 42/40 while trying to deal with this wandering issue I have. No synthetic yet but I have it and will install it at 5000 miles. As far as the other techniques I think I'm doing pretty good at them. According to the experts at Chevron, hills can reduce mileage an average of 20% so it's a big noticeable hit with a high mpg car like the Prius. Our gas in CA is probably lower in btu/gal but with summer here may be the same as the rest of the nation...not sure about that. I've only used the AC a couple of times but never very often. Most of time the inside temp is just fine here without anything or just a low speed fan. I don't think there's much mystery to it really. Hills and traffic have a big effect.

An example is my commute to work of 11 miles. I usually get high 50's to 60's and once even got 70+ including the warm-up. I've even seen 50 mpg first 5 min hitting the lights just right. It's a net slight downhill run. Coming home, the best I can get is 43 and it's often worse. I was using the EV button the other day and got 38 mpg! I got 55 mpg for the 20+ miles to the airport but only 45 mpg coming back...again hills.

But I have seen a steady improvement as the car ages so I'm at 47.2 mpg now and turned 48.6 mpg on the last tank. So there is hope!

 

first time on the Prius site.
Interesting stuff and so much more to read but your comment on the EV button caught my interest. What is it and what does it do? I, also, am not getting quite the spectacular MPGs as I thought I would. It is even worse in stop and go, 12.5 mpg versus 60!! Rather big difference and very disappointing.
A little crest fallen, Sue
Thanks!!

 

Hi Sue. Yes like they say, your mileage may vary. You'll find lots here about that. Hills, cold weather, slow stop and go traffic, short commutes of say 5 miles rather than longer ones greater than 10 or so, winter gas, all hurt gas mileage. That first 5 minutes is usually the worst for me and if I can get 50 mpg there instead of the usual 25 mpg, I know I'm going to have a good commute.

But there are people in areas like Florida, flat and warm, where they're getting very very close to the EPA numbers. I suspect that their mileage will drop off some when it gets really warm. But there's no getting around that 10-15 mpg when you're constantly starting and stopping. The EV can help some but I have not found it to be a big advantage. It helps me keep it in EV mode longer and up some gentle hills. But the battery goes down very fast and it isn't long before the engine must run to charge the battery up, even when you're just sitting there. So I think the gains are minimal or nonexistant. I'm happy to be averaging almost 48 mpg now with all the hills around here in San Diego. Increased tire pressure does help some. And synthetic oil might too. But it's not going to raise the mpg's by 10, more like 1-4 mpg if you're lucky.