10x displayed MPG til empty?

I think it does matter what your EV usage is.

Let's say I'm getting 50 mpg on gas and I've gone 500 miles on 5 gal. This means I've used EV for 250 miles and gas for 250 miles. My consumption is going to show 100 mpg...and by the 10x rule I have 500 more miles til I need to fillup. But, in fact, that only works if (a big if) I maintain the same EV ratio. If I suddenly find my self on a trip from SF to LA (300 miles) I will need to get gas long before I've gone 500 miles.

Mike

 

No...but look at what happens with your 10x rule:

500 miles, 250 gas, 250 EV, 100 mpg...rule says 1000 miles, 500 more miles (but really only 250)
600 miles, 350 gas, 250 EV, 86 mpg...rule says 860, 260 more miles (but really only 150)
700 miles, 450 gas, 250 EV, 78 mpg...rule says 780, 80 more miles (but really only 50)
725 miles, 475 gas, 250 EV, 76 mpg...rule says 760, 35 more miles (but really only 25)
750 miles, 500 gas, 250 EV, 75 mpg...rule says 750, 0 more miles (except ~0.6 gal reserve)

Yes, it is correct; just when you run out of gas... as it has asymptotically gotten closer to the correct answer. But if you had used the 10x rule on only the HV portion it would have been correct all along. Why fool yourself? Just push the button and use the HV miles.

Mike

 

Mark

I got a little confused. I see what you and 9gman are saying. Looks like that will work.

If you fill up to the first click, 9X should leave a little over a gallon of gas left in the tank.

 

I think the idea is to apply the rule every time you look at the MPG (Cons). So, the calculation you listed will (re)occur.

The same goes for a regular Prius. You may be get 55 MPG initially but as you drive faster, the tank average may drop down to 50 MPG. The same rule applies. It just need to be reapplied when you glance the MPG display.

 

Markabele,

I think the best thing you can do is to support the idea with your own collected data (as well as data collected by others) and see if the 10x, 9x, or other such number works out.

I collected my gas data from the get go with my car. After 2 years or so, I started looking at it to see if I saw any trends, especially when it had to do with range (like trying to get into the 700 mile club). It was then I saw that if I was around 10x displayed that I was adding about 10.5 gallons of gas to the car.

When I see people posting up in the 600 mile and 700 mile clubs, I do the mental math on their displayed MPG and try to figure out how much gas they should have added and compared it to the gas they did add. It works out really well and gets you closer to a real, functional range for the car.

I can't pioneer the calc for the PIP since I don't have one. But, I suspect between you, F8L and others, you'll be able to get a solid, collaborative value.

 

USBseawolf and others have the idea though. You could be doing 60.0 mpg for the first 500 miles and decide to drive 100 mph (160 kph) for some reason. Your Displayed MPG will drop like a rock, as will your range. But it will give you an idea when you need to fill up (10x displayed), it just won't be 600 miles anymore, but it will be over 500 miles.

 

Most of you are missing the point. What matters is what it says when you get to the last blip or so. At that point the MPG displayed has fleshed out over the entire tank. If you look down and you are on the last blip and you have 86 MPG you are pretty safe driving to 860 miles. Chances are you are sitting right around 780 miles at that last blip. The caveat is that you topped the tank off thus the 10X. If you don't top the tank off and stop at the first "click" my experience is that is only about 9 gallons in the tank, so I would do a 9x Rule of thumb. I go to the pump almost every 1,000 miles so for me it's worth it to spend the extra 3 minutes topping off the tank until I physically see gas in the filler neck. Those 3 minutes buys me 150+ miles or over bout a week of driving. Since I top off I know I always have 10.5+ gallons in the car So I know when my MPG says 95 on the last blip and I'm sitting on 850 miles for the tank I easily have another 100 miles UNLESS my HV/EV usage drastically changes.

My weekend is where I rack up my HV miles, so like another user said I also have gone an entire work week (150 miles) literally on an empty tank only to pull in and pump 10.5 gallons into the tank.

 

Anyone can use whatever method they think is best for them. I was just saying, as an example, if you are half way through a tank and you are starting a relatively long trip, you probably want to know if you'll need to stop for gas before you get there...or not. (I-5 SF to LA has a few sections with 30-40 miles between gas stations and even further if you want a good price.) It is simple enough to just toggle to the EV ratio screen and use that data rather than the data on another screen...which may give you an wildly different number.

If you normally drive mostly on gas it won't make much of a difference. OTOH, if you normally drive mostly in EV before starting a long gas trip, using the trip odomter and consumption number won't give you a good guess on when you will need to stop for gas.

Mike

 

It all depends on your EV ratio, IMO. On my prior 3 cars (2001, 2004, 2010 Prius) I generally used the 10x rule of thumb. With the PIP I've driven 600 miles on a tank and I've driven 3000+ miles on a tank.


I find it easier to just look at the EV ratio screen ...it directly tells you how many gallons you've consumed (assuming you reset it when you got gas). The problem is that it only shows an integer value. How many more miles you can go until you fill up is also quite variable. If you are on a road trip, you've just got gas to make you go, you can use the 10x rule...or 9x or whatever. If you are commuting daily and using only EV (as I do most of the time Mon-Fri) it could be 100's of miles and weeks until you need a fill up even if you are showing 10 gallons used and zero or one bar on the fuel gauge. I think I drove for 4-6 weeks with one bar back in Feb/Mar.

Mike

 

I don't do the 10x rule. I figured my Prius has about 11.9 gallons so (and this has been tested with the Gen3 non plugin) when the blinking happens, reset your current trip (or use trip B), only go MAX double the amount your MPG is showing (which will vary). A guy on the forums managed to go about 100 miles after the last blip blinks, but it would vary.

Now for PiP, how large is the tank? I would guess it blinks around the same time...then just go MAX twice amount your mpg is showing. I usually fill up at 1.5 and I'm fine, end up 10.3 gallons or so.

Now if you plugged in your car...it'll be a bit more complicated. You'll have to pay attention to when the car uses gas again