Reduced Range on Full Tank

possibly. the thing is, to get a better handle on it, you need to start tracking mpg/tank every time you fill up.

if you haven't done in the past, you have nothing to compare it to though.

how many miles on her? there are a lot of things in an 8 year old prius that affect mpg's. in fact, there aren't many things that don't.

 

You didn't state the mileage but with an 8 year old vehicle, it may be that the traction battery is starting to lose some of it's capacity which would force the gas engine to run a bit more.

 

DTE is calculated based on recent average MPG, so a reduced DTE on fill indicates either a recent lower average MPG or a short fill.

 

Has the EGR system ever been cleaned? Yours is at the miles they frequently give trouble. This ultimately affects the air/fuel mixture which is a key component in MPG.

 

Also, has the nature of your driving changed? Are you doing more short trips for example? That'll knock down the efficiency.

 

Welcome!

FYI, keeping it in EV mode as much as possible is not helping your long-term MPG. It will give you a short term spike because the ICE (internal combustion engine) is not running for a while. But that battery will need to be recharged... and when you think about it, all energy in a Prius ultimately comes from the ICE.

It's a different equasion with a plug-in hybrid because some of the battery charge comes from the electric grid. But in a standard hybrid, the ICE is the sole source of energy.

 

Some of the (recharging) energy your Prius uses comes from regenerative braking. Planning of routes and maximizing regenerative braking definitely does help MPG for me.

 

The car was put into motion by the energy derived from the ICE. So the regenerative braking is just re-capturing some of that energy.

 

Never the less it's impressive, recouping energy that'd otherwise be lost. You can do this on a very simple level without the regen too: just keep a good following distance, try to avoid hitting the brakes, coast up to slowdowns.

 

No question, the car is brilliantly designed. When you try to force EV, you're working against the brilliantly designed software.

 

Yeah I don't "force" it, but I do keep keep an eye on the HSI bar display (Hybrid Synergy Indicator??): if I've got plenty of charge I'll try to keep the bar just to the left of median, keep it electric-only. Once the state of charge starts dropping signif. I'll knock off, revert to pulse and glide more.

 

In September of 2019, I purchased a 2014 Prius V with 84K on it. The car salesman topped off my tank when he handed over the keys and the range reading said 475 with a full-tank. The station that we bought the gasoline at is "economical" and "guarantees" its fuel. On subsequent fill-ups, I used a different fuel chain with the "best" priced gas in town. The ranges started dropping. 450, 425, 415, 405, 395, 385, and then settled around 375 as the norm. This is not all that great for an 11.9 gallon tank.

Making a long story short, I started using the chain from which the car dealer had gotten my first tank. I would drive the vehicle until the range was near zero or at zero for a few miles and then stop by one of these fuel centers that "guarantees" its gasoline. I noticed that as the tank reached empty the car would not "take-off" with the same power as on a fuller tank. It was rather sluggish. My assumption was the "poor" quality fuel has settled on the bottom of the tank. It might have been "stretched" with water which is heavier than gasoline. This is why the "fuel" was likely less expensive at the other provider.

I also stopped by AutoZone and Advanced Auto and asked some questions. I was considering using a fuel additive product that I had used on my 1995 Toyota. It was called Berol B-12 Chemtool. It clears carbon and other pollutants from the fuel system. And, my Toyota dealer put a bottle in my tank each time I stopped in for a tune-up, after they changed the plugs and coil packs. But, the clerks recommended other products. I settled on SeaFoam for about $9.00 per bottle. I was told this was the best tune-up in a can on a price per value basis. However, the clerks each said the absolute "best" product for clearing out carbon was BG44K which cost $25.00 per bottle. However, one said the he used the Sea Foam in his vehicle. Using a can of Sea Foam additive on my last three tanks increased my range by 40 miles. It was 415 before adding it. Now, it is 455 without it. Simply, by changing fuel stations, over the course of five or so fill-ups the range had increase from a consistent 375 and reached the 415.

Also, I am scheduled for a regular mechanical tune-up in four months. Hopefully, my Prius will break that 475 or 500 range barrier. I am not a mechanic and do not specifically endorse any particular product, fuel station or additive. Your results might be different in your area of the country.

 

That displayed range is not based on 11.9 gallons. A couple gallons are set aside as safety margin or reserve, and not counted when computing range.

But MPG is far more useful than estimated range. What displayed MPGs are you seeing for each tank refill? Or better yet, what MPG are you calculating when filling up, if you do that calculation? (The displayed MPG is slightly "optimistic")

 

I'd say a bit more than slightly optimistic, getting Into embarrassingly optimistic territory, lol. Very consistently so, too: by design?

 

The range/miles-to-empty display is a projection based on past performance.

The MPG display is an projection based on the miles actually driven and an estimate by the ECU of the fuel delivered over that distance.

Manually dividing the actual miles driven by the actual fuel consumed is the only way to calculate true MPG.

 

Some will argue that the vagaries of fill-up procedure (pump clicks off sooner or later) will skew mpg calc, but it's not by much. And: any "zig" in one calc, will be compensated by a "zag" in the next. Calculating multiple tanks, the numbers get inexorably more accurate.

 

Exactly!

 

Have you ran a fuel system cleaner?