Erroneous fuel mileage readings

Under ideal conditions at low speeds, the various Prii are quite capable of 100+ MPG. Here is a chart for the Gen3 Liftback
Updated MPG vs MPH chart | PriusChat

If you are going downhill, high MPG is easier, though there is a payback required on the uphill return.

 

For a cold engine, the warmup cycle will kill any hopes for 99.9 on such short a trip. But if the engine is still adequately warmed from a prior trip segment, then it is game on.

2.8 miles should be too long for an EV-only trip.

 

It's not erroneous--99.9 is the largest number that can be displayed. In Gen 4, they upped the max displayed value to 199.9, I believe.

 

It isn't a "phenomena", it is a limitation of the measurement system.
99.9 is saying, in effect, not enough data to get a good reading.
And all of those numbers you report are likely pretty meaningless.

 

No, it does have a good reading, but the display is capped to a lower number.

We have threads here about how long we could keep the display pegged at 99.9. I've down over 80 miles, with a bit of help from gravity. The folks who are good at it, and have considerable patience, have down it much longer without gravity. While Japanese-market Prii don't have this same constraint, as they don't use English measures, their best hypermilers have done better than 100 MPG for whole tanks of fuel.

 

Sometimes.
But IF the fuel used is stuck at ZERO but the distance traveled is something larger than zero........the display is not capable of displaying the symbol for infinity.

 

99.9 in the display means 99.9 or more, which covers infinity.

 

Before I share my exact experience to yours, I get poo poo'd here of setting parking brake, switch gear to Park and go inside store for 5 minutes while car remains on Ready. There are two stores that I go to early morning weekends about 2-mile apart, when engine is at operating temp, going one store to the other, I push the accelerator down twice and EV the majority of the way to the other store. Trip summary is usually 99.9 MPG between those stores. I believe the amount of gas used to get to other store yielded 99.9MPG or better. I do fully block bottom grill during summers as necessary also.

 

Wait. WHAT ??
Summer is exactly the WRONG time to be blocking the grill.
And doing that is never "necessary".

 

If he is closely monitoring engine temperature, then it can be fine. One cool year here, I didn't take my grill blocks out until a hot day finally arrived in September.

But I will never recommend this late use of grill blocks to anyone, as it is so easy to not watch the (aftermarket OBDII monitor) temperature gauge closely enough.

So you are telling him that he should be achieving 99.9 MPG displays without ever having a grill block?

 

Thanks fuzzy1 I drive w hybrid assistant app all the time, displays ICE, inverter, mg1, mg2 and other critical temp status as I’m driving. My running errand weekend drives are no longer than 5 mins apart and no faster than 45 mph, temperature of ICE never goes above 180F and everything else is avg temp so I grill block safely. But my work commute is 50 miles w/95% hwy, no grill blocks allowed and get 65mpg per tank for past 6 months.

 

Sure. If you believe the fist part, why not also believe the second.

At low to moderate speeds, a "grill block" does virtually nothing good and restricts the air flow through the radiator and AC condensor and oil cooler (if there is one).
Then.....what if you get distracted and forget the block is there.....and it gets real HOT out ??

 

180F isn't even fully warmed. Normal operating temperature on mine is 195F.

When his engine isn't getting fully up to temperature ... see replies just above ... this is actually a good thing for efficiency.

Re-read above, he is not blocking these.

This is why I'd never recommend it to anyone. It is far too easy to flub-up and cause damage. But he is a big boy, knows the risks, and isn't endangering other people. If he messes up, he is the only one who will have to pay.

Many places, yes. But some of us live in cooler places.

 

It does help the engine warm up quicker as I’m driving off, and w/o the block, ICE on average is 10-15F cooler for weekend errands.

If it gets too hot because i forget to unblock, and engine overheats, I’ll just drive right into the local luxury car lot in a ball of flame crashing into their cars.

I check my engine oil and other fluids every other day, the only way for me to get distracted is if a very attractive lady hits on me and ask me for my number and wants to have 2.3 children with me as I get out of my car

 

Mine, 194F on 55mph hwy and up to 204F going 75mph in 100F temps, on redline oil.

 

I set a new record in my 2010 with now 174k, but was closer to 170k when it happened. I was in some hilly 30mph area with no traffic. It was about 3 miles and I averaged something like 92mpg at 25mph. I took a photo but can't find it. I think it's still accessible in my car's menu's, if you wanted specific numbers. My car had to of been warmed up already. One time I was on I-35 (Texas highway) and traffic was doing anywhere from 60-70mph even though most of it is 75mph limit and people normally do 80mph. If I reset it, I was getting like 70mpg at those speeds. But I didn't ride on it long enough to see what I could hit.

 

Are you using the AC too?

 

No, why?