Disappointing mileage

Just did my first fill up and only got 43mpg. I am not a heavy footed driver and I had the car in ECO mode most of the time. The first tank was 90% city driving consisting of an 8 mile commute to work each day on local roads.

Heck I get 38 mpg out of my smart car on the same commute, its only rated for 33 city driving.

Why such low mileage?

What was the computer showing? Was the tank full when you got it?

computer was saying 46, and the tank was full when I got it.

Did you personally fill it the previous time? Seeing all 10 pips on the fuel gauge does not count, it needs to be refilled that same way as last time.

Mine hasn't needed more fuel yet, but all previous cars can/could drive a significant distance just to get the needle down to 'Full'.

Does your commute consist of a lot of hills, or is it relatively flat?

Ok let me try to answer these questions.

1. I do not warm up the car. I start and go.

2. The dealer filled the tank the first time. It read full.

3. Very slight hills. Nothing you could not ride a bicycle over.

4. It is a local commute with several lights and fairly heavy traffic. So while not stop and go like a crowded interstate, I am going up to 35 and down to 0 often.

I had my car for four days now and still on the first full tank of gas (from dealer). I've driven it about 400 miles where about half of them on highway and the rest in town. I am averaging 53 MPG and there are some low hills in the area I live. Most of the drive was done in ECO mode with some tests of the PWR mode as well (short "trials"). AC has been on for 95% of the time.

So far so good, I hope to get it even better!

Its set to 74 and running most of the time. This is the south and it hot and humid.

Chances are it is some combination of what has been mentioned. The most likely main cause is that the tank was not completely full when you got the car. On my Gen II prius I could often go just over 100 miles before the gauge began to drop. I'll bet you will see a big improvement on your next tank driving the same way as you have been. Not time to be concerned yet.

These two posts explain the largest 'why' in assessing differences in fuel economy.

The most important factor in getting superior fuel economy is avoiding short trips.

A driver can do 65-70 mph on the highway from NYC to Miami and average 48-50 mpg. A driver doing the same 1500 miles in 100 RT commutes of 15 miles may only average 43 mpg. The biggest hurdle to overcome in getting superior fuel economy is the first 3-5 minutes of driving....in every vehicle.

If the total trip is 10 min then the car is 'efficient' for 5 min.
If the total trip is 10 hours then the car is 'efficient' for 9 hours and 55 min.

The weighted effect of the 'inefficient' driving is much greater in the first case.

The other day when I commuted to work - 10 miles one way, I got 68.7 MPG. This was up and down hills. In order to get the really great gas mileage, I've noticed that I must stay within the ECO line on the Eco Display, and as the DVD that comes with the Prius says, try to stay in the first half of the Eco zone.

When accelerating in ECO mode while staying in the Eco zone, acceleration is of course very sluggish, i.e. 0-35 in 15 seconds. The result though is you get really great gas mileage.

It's a trade off. If you are in Eco mode and are zippy (always in the red power zone), you're not going to get the great gas mileage.

You might consider checking your tire pressures to make sure they are consistent with each other (one not significantly lower than the others). Increasing the pressure will help with mileage.

Just to check the obvious thing first... Do you disengage the parking brake before you drive off?

tires are at equal pressure and are just above the sticker on the door.

Yes the parking brake is off.

How many minutes does your 8 miles trip take?

If you only go below 35 MPH, you have a golden opportunity for the P&G and potentially double what you are getting now.

47mpg wouldn't be too far off of the average I've seen so my guess is the car is still too new AND the dealer didn't have the tank completely full. Even my GenII can go 100miles and still show full.

I'd give it a couple months and see how it does with you filling the tank. Then please report back if it gets better or even if it doesn't.

Good luck!

My daily commute requires me to climb a 2000 foot hill 4 miles in length and I'm getting over 50 mpg. Without the hill I'm around 60 mpg. In my previous 2006 Prius, I was getting around 42 MPG with the hill in my daily commute. So far the 2010 is getting 8-10 MPG better than the 2006 for me which seems about right from what I read.

It does take some 'Prius tricks' to get the mileage up. I stay in the ECO zone as much as possible. I get up to speed fairly quickly usually in the power zone and then let off the gas and spend most of the time in the ECO zone. Anything under 25MPH I'm in EV mode as much as the vehicle will allow.

How many miles were on the car when you purchased it? Spirited test drives could have affected that first tank full. Got mine with 10, after 50, the mpg was only 39.3. You can see by my signature the average is much better now. I expect to get 55+ when things settle in.