First Fillup

woo hoo!!! congrats andwelcome, all the best!

 

Welcome and congratulations on your Prius Plug In. Enjoy the fuel management aspect.

 

welcome....youre gonna love it! I still am amazed by mine each day.

 

Congrats OP!!!

Just a quick thought and question to everyone while we are on the topic of fill ups.

It's obviously not as easy for all our math, but is it best for someone that uses primarily EV to never keep their tank more than half full, maybe even a quarter full? Two reasons: less weight and fresher gas. Thoughts?

 

Have owned mine for a full year now. I always aim for 1000> miles per tank.


iPad ? HD

 

I've had my plug in since late January. I'm on my second tank of gas (less than half), counting dealer fill up at purchase. I asked the same question. A full tank adds about sixty pounds. Most say it's a non issue for both of your questions. Currently at 2060 miles, my last fill up was March 3. My EV ratio is 67%. Very happy with my choice.

 

nothing wrong with saving weight if you really don't use much gas. i don't think 5 gallons is 60 pounds. and two gallons sits in reserve. what level are you comfortable filling up at? as far as freshness is concerned, i didn't have any problems going from january to may, and the ice fires every 125 miles anyway.

 

Unfortunately math says it's not a non-issue. When I had a Gen3 I think we estimated that an extra 50 lbs can cut off up to a full mpg, which would probably equate to 1-2%. That doesn't seem like much but a great hypermiler will take every little scrap of fuel economy they can get.

There is also the cost averaging factor as well, in terms of prices at the pump. I don't have to worry that prices will go down after I just filled my tank for the next month. Of course, if you know without a doubt that prices will rise and stay higher for a while then I suppose this is all moot.

 

Gas weighs 6.2 lbs per gallon saving over 30-35 pounds for the whole run of the tank.

 

it's not enough to notice mpg visually, but i suppose every little bit helps!

 

Being a scientist I appreciate the effort to save weight. Yet one feature of the PiP is that one will spend less time at gas stations. Filling up half-full would negate that benefit. I note that comparisons always compare the price of elec. to the price of gas -- but in my opinion time saved at gas stations is an important plus to the PiP. Of course, that must be balanced against the time spent plugging in the cable (not to mention time on PriusChat :>), and stressing over the days when I forget to plug it in!

A question: The battery icon in the display seems to behave strangely. Most of the time the bars indicating charge drop as the charge drops, as one expects. But at other times it shows full when there is no electricity stored.

 

Yes, topping off seems the best way of getting an MPG number that takes everything into account. If I recall, on my 2005 Prius, the number of miles on a tank divided by the amount of gas added did not always yield the same thing as the dashboard gauge for MPG. But an issue was the variable-size gas tank in that car (smaller when colder because of rubber). That problem does not exist in the PiP, so I am hoping at least for consistent results (compared to dashboard gauge) when I do the actual computation, and it will be interesting to see how that compares to the MPG as given by TRIP A, which it makes sense to reset on fillups.

PS: A physicist friend did confirm that it is reasonable to expect a 1-2% decline in MPG due to carrying 50 lbs. Somehow that still seems high to me, but I guess it is possible. Thank goodness the batteries do not weigh more when completely charged!

 

I don't think that seems high. If you are getting 70mpg that means just 7/10 - 1.4 mpg...
but I'd point out that its not 50 lbs for the whole tank - if you go full to nearly empty then the average would be carrying 25lbs. Given that I'd think your cost would definitely be under 1 mpg

also I wonder if your friend considered that would only be when you are using gas ?
I'm almost at 90% EV... put another way - if you were 100% EV it wouldn't cost you ANY mpg

 

Why does added weight decrease the MPG in a hybrid? It takes more energy to get the added mass up to a particular speed, and that energy is lost when braking with a conventional car. But with a hybrid, you get that energy back with regeneration. Are conversion losses the issue; i.e., you only get some of the added energy back? Is the MPG loss due to added weight less in a hybrid? And even less in plug-in, which allows a higher regeneration rate due to the battery technology?

 

fortywok: I don't believe your comment about EV mode being better as regards the extra weight. Extra weight means the EV runs out sooner since it is driving a heavier vehicle, and more gas is used hence there is an impact on the PiP's overall mileage figure. I guess if you were driving 100% in EV mode so that you never ran out, and so had some extra in the battery to deal with the heavier weight, then indeed you would be correct!

And yes, the fact that the tank of gas gets lighter as one uses it up does reduce the damage.

CharlesH: The regeneration is far far less than the amount driven. It can take 0.3 or 0.4 miles on a downhill to regenerate what is used when driving 0.1 mile. But still, the time spent at gas station is, for me, the deal-breaker when it comes to filling less than a full tank.

 

The PiP prototype model was heavier and if I recall, it got EPA rating of 49 MPG combined in hybrid mode.

 

When you run out of plug-supplied electricity, the battery icon changes from EV to HV view. See the difference...



If it didn't do that, you'd have no clue how much regular hybrid (non-plug) electricity is still available.

 

It's just logic.
If that roughly 1% cost of the extra weight is correct then : say your EV range is 13.0 after full charge - that means your cost of carrying the weight of a full tank is just 13/100 of a mile (lets call it 1/10) so now EV is 12.87.
Thats not going to affect your overall MPG - I'm at a ridiculous 89% EV = 600 MPG because I can charge up after almost every drive. Therefore your gas cost is negligible for me or anyone who doesn't need to tap that gas.

IF there was no EV at all and hybrid MPG is 50 - even then your 1% cost is .5 MPG.
So a more normal PiP driver at 50% EV would experience a cost of 2.-.3 MPG

- and we did agree that the tank weight (and cost) will decline as that tank empties