So I just added my second tank to the database on my new Prius - my first tank got just 47.6mpg, and my second, 51.5 - that's a pretty dramatic difference. In hindsight, I didn't know how to reset the average MPG on the Consumption screen when I left the dealer lot (I know how to now) and, when I was handed the car the average MPG was below 40mpg, and had 36mi listed even though the odometer only showed 4mi.

Should I throw out that first tank, or keep it?

Prius 2006, bought September 14:

Hi,

If it were just me, throw it out if it bugs you. My first tank, 39 MPG, s*cked too. My first tank was so bad that I used the rest of my 'pickup the car' trip to map MPG vs MPH. Three months later, I realized that one tank delayed my hypermiler star when I went over 3,000 miles. So I asked a simular question, may I drop my first tank as a 'learning experience?'

The chorus in January 2006 was, 'Oh no, every tank is important.' I thought about it and realized the hypermiler star was bullsh*t because these same voices didn't say, "Because we use your data to help everyone get better milage." Since then, the chorus has wandered off.

My thinking is if you have some 'lessons learned' that can be illustrated from that first tank and are willing to share your lessons learned about it, keep it. If not, then it really doesn't matter. It comes down to where to you want to be a year from now.

I'm still here and so too is my first, 39 mph tank plotted on this MPG vs MPH chart:


In one year, I've put 20,000 miles on my NHW11 Prius and know how to get just about any MPG result I want and share my lessons learned. I am also working on projects that expand the capabilities, performance and life of the NHW11 Prius. Sad to say, I've also learned some lessons about the chorus and I'm staying here with my 39 MPG tank.

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.

Call me naive but, what gets you a Hypermiler star?

Yeah maybe I'll just let that one tank sit and drag my average down less and less as I drive... . I think I was just looking for someone to take the guilt away from throwing it out, but it bothers me so much from a scientific perspective to be choosey about what data I get. It also bothers me a lot that I was handed a car with terrible MPG before I even got started... but... less... maybe.

By the way Bob I appreciate how much information you bring to this forum, it's a treat.

Prius 2006, bought September 14:

It takes getting better than EPA MPG for a minimum of 3,000 miles. You need to also set your ratio of City/Highway. But that makes more sense if you realize that the average EPA city speed is ~25 mph and the average EPA highway speed is 48 mph. I'm lucky that both of these are well within the ranges of my commuting route.

It is a judgement call. If you can identify some characteristic of the first tank that would help others, keep it. If it is just "whatever came off the lot including everyone who took it for a test drive," drop it. The quality of data is not just the dependant value, the MPG, but the independent variables that led to that result.

I have been impressed with your researching posting history. You've picked up and added to old threads. Too often we see folks who pop-in, ask a question without researching the background and then wandered off. I think we're going to have a lot of fun expanding the envelope.

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
Free speech, dialog and knowledge thrives without the poison of SPAM.