Then I'd never know where the real bottom of the tank is, in case of circumstances where I can't refuel. Or am faced with serious price gouging. BTDT. As mentioned very recently, my past cars have displayed fuel gauging differences corresponding to more than 2 hours of driving range, close to 3 hours since I learned hypermiling. That is a huge uncertainty. Commercial airliners, which face vastly larger consequences for miscalculations, routinely land with less margin. Characterizing the real range of a specific car requires intentionally running out, or running low to achieve refills close to the manufacturer's claimed capacity. I do that at a time and place and circumstances of my choosing, well before any urgent situation arises.
I'm not following that reasoning, unless you think that forced charging followed by EV mode is more efficient than HV mode.
Maximizing the SOC when burning the last of the gas improves the margin to continue when the gas runs out. My first test did not reveal a specific signal or code that the last of the gas was burned. The car becomes an inertial mass, coasting, and has to be 12V reset to acknowledge adding a spare gallon of gas. I consider this to be dangerous. With any EV range charge, 80% if the charge mode is used, will give ~20 miles to reach gas or a safe place to park. Bob Wilson
I can understand an argument that says 'easier to get going again,' but I still don't follow why forced charging gets you further down the road. Please correct my following (made up) example: HV: 38% efficiency to shaft Forced charging: No more efficient than HV, likely less and with additional conversion losses EV mode: 95% efficient
I recommend it for safety. If you want distance, turn off every optional load, roll up the windows, abandon extra weight and drive on at 20 mph. Bob Wilson
So you would use up the EV miles, then use Charge Mode to build it back up in case you run out of gas? If that's the goal then it seems like it would be more efficient to simply not drive in EV mode so that the battery remains charged and always available if needed. Of course that means the battery then becomes just a very expensive gas can. If safety is the concern, what might be better is to not use EV during the first part of the trip, and only turn it on when EV miles = MTH (Miles to Home). If you accidentally run out of gas before then, you will have a full EV charge to hopefully get you to a gas station. If you don't run out of gas before EV miles = MTH, then you can switch to EV and arrive home with zero EV miles remaining which is the goal. Might not be the most efficient way to use the EV miles, but it would give the same safety cushion without having to use Charge Mode.
I have done two, out-of-fuel experiments: Without battery charge while in HV mode -> the car silently becomes a rolling inertial mass with no indication that the last of the fuel was just burned. The car becomes a rolling mass regardless of location and could easily result in being a hazard in traffic. The details: [WARNING] Running out of gas | PriusChat With any EV battery charge while in HV mode -> the car silently switches to EV without changing the state indication from HV (i.e., the mode remains blank.) This switch can be detected by watching the EV battery SOC decrease while the car continues to drive. The details: How to run out of gas | PriusChat Since "charge mode" can be turned on when the "empty" icon comes on, use it to bring the battery up to 80%. Then when the car finally runs out of gas, the decreasing EV SOC will let you know 'it is finally out of gas'. This gives you +20 miles of range to find gas or a safe place to park. The "empty" gas icon comes on with about 1 gallon of gas remaining in the tank so there is plenty of energy to convert to EV charge. Now there is an open question of how much gasoline is consumed to put an 80% charge on the traction battery? I don't know, yet. That is really part of a larger question of how much gasoline puts what % on the battery. A technical question, nice to know that could be experimentally verified but my interest is in safety. When running the gas tank empty, the Prime is much safer with any EV charge because the decrease lets you know the tank is dry. Bob Wilson
Okay so technically the warning you get is low on fuel, not out of fuel, correct? And you are saying if you get the low fuel warning, to first see if you have some EV miles remaining, if not then run Charge Mode for a few minutes to get a least some charge, so that you can use the EV meter as a makeshift "out of fuel" meter. That is mystifying though that you get a warning at approx. 1 gallon, but no warning when you actually run out of gas. In my Gen 2 I get a visual and audible warning at approximately a half gallon, then when the gas runs out the dash lights up like a Christmas tree. It was about ten years ago so I don't remember all of it but I seem to remember it turned off the radio and climate control, presumably to conserve enough charge so that you can find a safe place to pull over. I realize from the other comments there is the opinion to simply don't run out of gas. But for the rest of us who do make a mistake once every ten years or so, a warming light and sound would be appreciated.
My one and only experience running out of fuel in a Prius left me with enough battery charge to drive over 0.5 miles to a fuel station. I'm surprised that Bob has net seen the same in the Prime (or more.)
What 1000 mile club? I drive 90% of the time 50 miles to an EV station. I constantly get 110+ mpg now and 1,000 miles tanks. I'm about ready for my maintenance and only filled up 5 times :O
Yeah.....I guess the 800-mile club thing is rather passe. Toyota claims that the Prime has a range of 640 miles. This, Toyota gleefully points out is far superior to the Volt's mere 420 mile range. This value is still relevant to those who travel or do not like to refuel (either kind) and it represents a capability that cannot be known for sure without testing. Range is either relevant or it's not.
My testing with the Gen-1 was like yours and exactly how I felt it should work. When the car actually runs out of gas, we should have unambiguous signals so we can use the remaining traction battery to reach a safe place to park. Sad to say, some folks have not understood that these are separate things: low gas warning engine stopped because there is no gas This is compounded by the problem that three failed start attempts in the earlier generation Prius required a 12V power-on-reset or a tow to the dealer. The dealer then uses a Techstream to reset the flag and overcharges the owner for letting the car run out of gas. With the Gen-3, I had found a subtle 'engine stopped because there is no gas' signal, the absence of power flow arrows. This was shared with the PriusChat community but as you noted, sparking all sorts of 'tsk tsk, I never run out of gas' nonsense. But the Prime is (was) worse. The first time I ran the tank dry, there was no warning. Worse, adding one gallon that worked with our Gen-1 and Gen-3 did not work. I had to do the 12V power-on Reset. Fortunately, I was prepared. So that is why I ran the tank dry a second time only with an EV level charge. I was able to continue at reduced power but keep up with traffic. Monitoring the EV SOC decrease showed it was working in EV mode, there was no dash indication. So it was a non-issue for me. Now that we know how it works, when someone does the unprepared experiment with the dealer tow and charges, we can sympathize and explain what happened. Bob Wilson
I'm following now -- thanks for the patient explanations. I suppose that if I run into this situation I might force charge for a mile or so of range to avoid the 'Prime as a brick on the highway' mode. More than that would be counter-productive since it would just reduce my remaining range. I agree with you that most owners will not be quite so informed and the unlucky ones who run out of fuel will experience brick mode.
This may be a silly question, but how did you get the 90% (I am assuming it's the traction battery charge) show up in the HV monitor window? I usually see estimated range there in miles. iPhone ?
If you are driving on an empty tank but still have battery left, do you run into the same problems of the car not recognizing a one gallon refill that requires the 12v reset ?
Do note that for a legitimate 800 or 1000 mile club entry, to compete in the same spirit or class as other cars, plug-ins must count their battery as part of their 'tank'. That is, no midroute recharging either.
Given the excellent HV mileage and 11.4 gallon tank, it would be trivial to maintain the +88 MPG average. I've done it before with our Gen-3 and this car is so much easier to get stellar MPG. Bob Wilson
In the last eleven years, I have run out of gas twice in my Gen2. Both times, the traction battery was able to get me to a gas station. Although, I heard somewhere, it is not good to let the car run out because gas also cools the fuel pump. Does anyone know if this is true? (perhaps a previous debate?) Thanks, Steve