Avg. MPG gave DROPPED!!!

i have seen similar of my 2006. i think it means the health of the HV battery is deteriorating.

 

A failing 12V battery has also been known to cause falling MPG. Fixable at much lower cost than changing the HV battery.

Frozen or dragging brakes have also hurt MPG. This would be betrayed by overly hot brakes or wheels.

Low tire pressure also hurts MPG, but not by this much.

 

failing 12V, too? this is really good info! it gives me some hope!

 

Here is the top thread on that:
Weird stuff happening? MPGs dropping? Test The Battery | PriusChat
Do note that while certain posters reflexively blame almost everything on the 12V battery, it isn't really really a universal culprit. Other things go wrong too.

 

12v if more than 4 years old is a suspect especially if votage is below 12. Alignment and low tire pressure also can hit the mpg hard. Are you overdue for spark plugs? 120k interval.

 

Do remember that new tires will temporarily reduce MPG, and a non-LRR tire choice will drop it even more, for the life of those tires. But even together, these can account for only a portion of your MPG loss, not all of it.

 

Mines (04 prius) is currently getting 34.5 mpg and its usually around 39-41mpg. What I have noticed it that the AC drops the MPG and the cause for mines sleeping in the car during lunch with the AC on. This kills the MPG. That being said Im about to clean the mass air flow sensor, throttle body, PCV valve and change the spark plugs here in the next week or so. Hopefully that reclaims some MPG.

 

let us know!

 

If I understand you correctly, you are in the stationary car for an hour (or so) with the A/C on (presumably around 68-72℉). If this is correct, then that will affect your ability to get MPG anywhere near the 44-50 MPG (5.35-4.70 l/100km) mark.

It is the reality that the A/C when used at the extremes is a heavy user of electricity. There is just no way a round it.

I think that no matter what you do, if you keep using you car this way, you will always get below average MPG. There is no such thing as a free lunch.

 

I use a Prius daily for work, and if we idle for an hour or more the mpg on the mfd shows 36 to 37 mpg. It does go up as you drive, but I have noticed that when you do tue lath the oldfashioned way, you are indeed averaging a higher mpg. We do get a lower mpg from idling, but thats a small price to pay for comfort in very hot weather. If your mileage continues to dip lower, I would check the aux battery before anything else, especially if you do not know when it was installed or is the original.

 

One more possible culprip: the gasoline in the tank. It's not widely known, but ethanol has much less energy/volume than gasoline. While "E" blends do raise octane (i.e., slow combustion rate), they sap power, thus reducing MPG. The higher the percentage of ethanol, the lower your MPG. Ethanol may also cause deterioration of rubber engine components in concentrations greater than 10%. Bottom line: AVOID ethanol blends any higher concentration than "E10" for best performance and least engine wear. Opt for "Top Tier" gasoline every time over high ethanol alternatives like E20, etc.

 

I had something similar happen to our 2008 last year. Dropped into the 30's. I monitored the battery but found nothing wrong. Then I noticed it had to do more with the PIP than in EV mode.

I dumped a 1/2 can of Seafoam in the gas tank and within a short time my mpg's were back to normal. I guess it was dirty injectors.

 

No:

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