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I intentionally ran out of gas in my 2025 Rav4 PHEV

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#21 ·
PetitFrereRav4 said:
I don't know if this sounds correct or not but this is what I got yesterday. My DTE had 1 mile left. I went and got gas. All I could get into the car was 12.9 gallons. I do not overfill. I stop at the first click of the gas punp to stop putting gas in the car.

Say the gas tank is 14.5 gallons. 14.5 - 12.9 = 1.6 gallons. Does this mean we have only 1.6 gallons when DTE turns to zero? Does tjis mean I drove for 97 miles fr ok m only 1.6 gallons of gas left before I ran out of gas? Here are pictures.

How many actual miles did you drive on 12.9 gallons?
I also drove one time like this. But I drove 560 actual miles on 12.8 gallons filled. And many times I drove to Zero miles left (but did not record actual miles) on 11 gallons filled.
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#22 ·
dt123 said:
I wonder, why did it say "Engine Stopped -- Stop in a Safe Place within 6.2 miles"? The meaning is clear enough, but why is it saying that?
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For one 6.2 mi is 10 km (km, the rational units used by most of the world), so that explains the fractional part. Why 10 km? Perhaps if you had used it in EV/HV mode, then the EV would be zero, but they leave a little in the battery for this situation, like 10 km's worth. Just a guess.
 
#23 ·
iowagold said:
Soooo
When it stopped the engine for low to no fuel
It continued without any surging right?

My question is did it stop calling for the gas engine as a preset condition
Or a tank level or low fuel pressure?

What software sense and conditions stops the call for restarting the engine?

I would love to see the flow chart on the software on this
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A flowchart from Toyota? They may not have one, which would help explain why their software is crap.
 
#28 ·
eugenepowers001 said:
The electric motor is used no matter what. I did not see any better mpg. The period of time these gained EV miles are used is too short to notice anything.
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Yes, it would be difficult to measure, but if the battery is being depleted while driving, the car is using less gasoline to move the car than if the battery level is remaining relatively constant.
 
#30 ·
eugenepowers001 said:
But why is the battery is being use if in HV mode? This what doesn't make any sense.
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The H in HV mode stands for hybrid. In hybrid mode the battery kicks in to assist the ICE engine. That is where you can get the full 302 horsepower, combining the ICE and the electric motors. It is how you get better mileage than a full gas R4. The ICE engine shuts down at low speeds (traffic) or stops. The traction battery keeps a reserve to maintain the battery for hybrid mode.
 
#31 ·
Gymnbat said:
The H in HV mode stands for hybrid. In hybrid mode the battery kicks in to assist the ICE engine. That is where you can get the full 302 horsepower, combining the ICE and the electric motors. It is how you get better mileage than a full gas R4. The ICE engine shuts down at low speeds (traffic) or stops. The traction battery keeps a reserve to maintain the battery for hybrid mode.
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In that case the battery should be completely discharged very shortly but it doesn't happen. It only discharges what it gains in regen very quickly and then stops.
 
#32 · (Edited)
I would assume the concept and functionality of the DTE is the same in the prime and hybrid versions. I like using the Trip A display for my "fuel gauge". DTE has a built in buffer in its algorithm for obvious reasons. I get around 5 L/100km per tank and with a 55L tank I have a theoretical range of 1100 kms. The DTE in my '24 R4H seems to be more accurate if 0 DTE is meant to be when the low fuel light comes on. The low fuel light comes on anywhere between 900 - 1000 kms on Trip A. The manual says there is ~8.3L of fuel remaining when the low fuel light comes on - equating to ~166 kms remaining at 5 L/100kms. DTE is normally anywhere between 50 - 100 kms when the low fuel light comes on.

Immediately after filling up, the DTE has never initially displayed the theoretical range of 1100 kms. As far as I recall the initial DTE display after filling up has been anywhere between 970 - 1040 kms - strengthening my belief of a built in buffer in the algorithm.

I also display on the mid the average fuel consumption since last fill up and as long as it stays at 5 L/100km +/- 5%, which it normally does, then I know I can safely get at least 1000 kms on Trip A before needing to refuel, regardless of what DTE displays.
 
#33 ·
eugenepowers001 said:
In that case the battery should be completely discharged very shortly but it doesn't happen. It only discharges what it gains in regen very quickly and then stops.
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In HV mode, the battery frequently shifts from being charged and discharged. HV mode attempts to maintain the same number of EV miles that it had when HV mode was started. If there is a long hill and the battery gets charged with a few more EV miles, the ratio of charging to discharging is no longer about even, but it is skewed toward more discharge until the EV miles gets to the starting point.

If you forget about the prime and just think about just a hybrid with a very tiny battery compared to the prime, the hybrid works the same way. HV mode is hybrid mode where essentially the car works like it is just a hybrid car without EV mode.
 
#34 ·
Don't put 100% faith in either the EV or HV range numbers on the guess-o-meter. If you are on a road trip, and the gas gauge is between "E" and the first mark, stop and get gas as soon as possible, especially if the traction battery is depleted and you don't have any EV range as an emergency backup. The A25A-FXS engine uses both port and direct injection, so there are 2 fuel pumps, a low pressure 37 psi pump for the port injection, and a high pressure fuel pump that delivers 3,000 psi to the direct injection rail under heavy loads like climbing steep freeway upgrades. Running out of gas probably doesn't hurt the low pressure pump, but air bubbles in the high pressure pump could cause cavitation, and that's usually harmful to any high pressure pump.
 
#35 ·
tarapup said:
Why 10 km? Perhaps if you had used it in EV/HV mode, then the EV would be zero, but they leave a little in the battery for this situation, like 10 km's worth. Just a guess.
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Could be! The bottom buffer of the battery is about 2.5 kWh (i.e. ~14% of 18.1 kWh). And 10 km is almost exactly how far you'd be able to drive with that amount of energy.
 
#36 ·
Thanks for performing and sharing the test. I own a 23 RAV4 Prime and one thing of note is that the fuel (and EV) miles to empty is a rough estimate based on past driving. So, even if it says 0 it is an estimate. I found the fuel bar is a more accurate representation of how much fuel is left. An extreme example is when I tow a trailer. Realistically I am seeing 25 mpg (I track miles driven and how many gallons I fill) and can only drive 200ish miles before the bar drops to almost empty, yet the miles to empty on fuel still shows 100+ miles to go. If I continue to tow and fill up, each fill up the fuel miles to empty continues to drop, but it will never drop to what my realistic miles per gallon is getting. I assume it is because realistically the RAV4 Prime should never be getting 20-25 MPG. Just thought I’d mention this finding in case others notice a difference between the fuel bar and miles til empty. If someone drive differently between fill ups (aggressive driving vs economical driving) it can have a similar yet less drastic impact on fuel miles to empty than my towing example.
 
#37 ·
PetitFrereRav4 said:
Some people have done this test..This is my own personal experience. YMMV.

View attachment 219993
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The most important take away for me was...I'm living in the wrong state! If you visit Los Angeles, that 14.3gal will be about 60 bucks :cry:
Hope you are enjoying the Prime, I passed as I drive so little miles, the $12K premium here would buy years of gas.
 
#38 ·
forget Los Angeles, try San Diego! worse than LA.... of course there's some $10 a gallon stuff in rural California.

I love my prime, got in late '24 and have only put about 4 tanks of gas in it...
 
#39 · (Edited)
eugenepowers001 said:
But why? The whole idea of regen is to gain and save the range.
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Perhaps the several great replies from @wscan and others in this discussion have satiated your questions, but I'll amplify from another angle.

IMHO, the whole idea of regen is to convert kinetic energy into battery charge rather than brake heat. Once it is in the battery, it is treated the same as the rest of the available charge.

And where does this range go while in the HV mode?
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Hybrid mode is continuously using the battery in variety of scenarios. One moment the battery is powering the car while the ICE is shut off at a stop light. Then it moves the car off the line before the ICE restarts. Then it may throw in some extra torque when the gas pedal is pressed hard. And it also maintains the 12V system. Between these events it captures regen energy from coasting, braking, or speed adjustments from radar cruise.

The goal of the car's HV mode brain is not to hold the battery to any precise SOC, but to think of it like the smaller battery in a pure hybrid model that aims to achieve maximum efficiency by a) never depleting the battery, and b) never running out of charging capacity to take advantage of regen when it next occurs. All this while trying to maintain the SOC value present when the car was switched from EV to HV mode.

The RAV4 Hybrid battery is rumored to be less than 10 percent of the Prime's 18 kWh battery, yet it achieves virtually all the promised efficiencies of the hybrid concept. It is my guess that when a Prime is switched to hybrid mode, it takes note of the current SOC, then defines artificial boundaries above and below it, spanning ~1.8 kWh (for sake of discussion). That way the same hybrid mode efficiencies and driving dynamics that evolved in Toyota's hybrid cars could be grafted into the Prime siblings quite directly (ignoring all the other operations unique to a Prime vehicle).

This is just a conceptual discussion, as the control algorithms are vastly more complex than we can ever know.
 
#40 ·
gregeusa said:
forget Los Angeles, try San Diego! worse than LA.... of course there's some $10 a gallon stuff in rural California.

I love my prime, got in late '24 and have only put about 4 tanks of gas in it...
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That "rural California" gas! US-395 between Minden and Ridgecrest, yikes! There's places on that route, like Lee Vining and Big Pine, where gas is $2.50/gallon more than it would be even in the San Francisco Bay Area, which is where I grew up and first learned to drive. I thought at the time (mid 1970's), "there can't possibly be anywhere else in the world with more expensive gas than San Francisco!" - That is, until I first visited Death Valley in 1982 and drove home on 395, and saw what it costs to drive a vehicle in Mono and Inyo Counties!

I have a 2023 R4P, purchased 2 years ago this month, and now with about 22,000 miles on it. I'm averaging about 80 miles per gallon of gas purchased. The actual fuel consumption is about 44 miles per gallon, with the other 36 miles being in EV mode. with the energy coming from external battery charges. I pay about 9¢/mile for gas in HV mode, and 3.27¢/mile for home charging when driving in EV mode. My total energy cost for gasoline and electricity fluctuates between about 6 to 7 cents per mile, depending on the current price for regular gas, and the proportion of EV to HV driving that I do from one month to the next. If I don't take any long road trips, and most of my driving is in EV mode, that cost drops to 5¢/mile, or if I take a couple of road trips, with maybe 900 miles in HV mode, that month's energy cost drifts up to 7¢/mile. But contrast this to the last ICE car I owned, a 2014 Subaru Outback: that car only got about 25 mpg, and if I was still driving it now, it'd be costing me 16¢/mile. So the Rav4 Prime is saving me $1,200 per year in fuel cost for 12,000 miles at $4.10/gallon.

Now, I could have bought a Rav4 Hybrid, and saved about $12,000. To be perfectly honest, the Rav4 Prime will never save me enough on fuel to recover that $12,000, especially if the traction battery craps out after the warranty period and I have to replace it. But the car is fun to drive, and it's especially a joy on twisty mountain roads, where that heavy battery gives the Prime such a low center of gravity that you can zip it through corners with way less body lean than a regular ICE Rav4 or Rav4 Hybrid.
 
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