125 Fill-Ups; 58,000 miles; ~50 MPG

I've gone past a few milestones without reporting in on performance of my 2010, but I think I'll provide a few updates over the next week or so. One of the interesting counts I've undertaken is the amount of times I've gone to the pump in the time since I moved from Gen II to Gen III. This past week was my 125th fill-up. When I made that most recent purchase Tuesday, in Valparaiso, Indiana, I added the 1,166th gallon of gas on the 1,176th day I'd owned my Prius V.

My odometer that day was reading 58,090. When I picked up the car from the dealer on May 25, 2009, it had a reading of 12 miles. During those 58,078 miles of enjoyable driving, I've enriched various gas retailers a sum of $3,678.94 while purchasing 1,166.178 gallons of regular unleaded gasoline (with summer blend in season and almost always with 10% ethanol).

To save you the mad scramble for your calculators, I can report the lifetime fuel use rate comes to 49.80 miles per gallon.

The MID has a different view of my fuel use, and I would like to "have what she's having" and believe my mileage truly is 52.7. Instead, I'll go with a liberal rounding and say:

"Yup! For the lifetime of my car and counting every drop of gas, I get 50 MPG." (EDIT: See later post about a graph showing mileage trends.)

By some additional and almost fun calculations, I've determined my savings during this period, assuming the alternative is a car offering 30 MPG, exceeds $2,428. Not bad. If only I could find a car with mileage as high as 30 MPG (real performance) that gave me all of the features of my Prius V with the ATP, such as leather, 17" wheels, radar, lane keep assist, etc., that would cost $2,500 LESS than my Prius did . . .. I'd probably have found a Car and Driver "Car of the Millenium"!

Instead, maybe I've found the elusive Hybrid Premium!

 

I've been on a bit of a self-imposed "hiatus" from PriusChat. I'd check in every once-in-a-while, but I felt I needed to step back a bit for two reasons. First, I was taking too much time away from higher priority activities (and persons), even if it was only a "short" time every day. Second, I was wondering whether I was drinking the KoolAid and thinking it was simply water.

I don't know that I'll be spending quite as much time on PC as before, but I'll put a bit more time in again!

Also, I'm glad to report I wasn't too skewed. I still believe the Prius is the best car out there. I'm intrigued by the newer offerings, especially the Ford line. Nonetheless, for the price, performance and reliability, the Prius remains the go-to car.

I'll agree, though I suppose Alaska winters are a bit tougher on MPGs than the Illinois variety. The killer this year has been the incredible heat and humidity. I had a couple of sub-50 tanks this year when hauling the family and "stuff" through 100 degree weather. In prior years, the same trips, even with the A/C on, were still getting mid-50 tanks.

Age has something to do with it, too. I'm analyzing the data a bit more, and I'll see if there really is an overall downward trend in FE.

 

Nice to hear from you, John. You're back into the "heady" days of discovery, where I'm still in the hunt for finding out how far and strong the first Gen III will go!

I do believe my mileage has been receding. A bit slower than my hairline, but it seems noticeable.

 

I've taken a closer look at my fuel economy across the years, and it is clear there are a couple of variants and trends worth observing:

1. Mileage Varies Seasonally. This is hardly a surprise, but it is much more apparent when looking at data on the same car in the same locale across a three-year period.
2. Mileage Drops Over Time (Perhaps "Miles). This could be explained by any number of variables in my driving (of which there are a couple worth noting -- see below), but I believe the trend is solid enough to be a valid point.
3. The Prius is Built to Deliver High Mileage. No matter how you cut it, you will not find any car with interior room for 4 adults plus significant luggage, with solid road handling (the 17" wheels and low-profile tires are great!), and with all sorts of great electronic gadgets (the ATP is pretty fun and sometimes amazing), that will get anywhere close to 50 MPG.

Self Examination. There are any number of factors which could have led to trends toward lower MPGs. Though I don't think any of these outweigh wear on the cylinders and the inevitable drop in pressure. Remember, I've been driving the car 39 months and for 58,000+ miles. Here are the other changes which may or may not be factors:

• I've become more interested in comfort and ease of driving than getting high mileage. Most people will believe this is the answer, in and of itself, to lower mileage. I don't know that it is. I've had more than six years nearly 100,000 miles of Prius driving experience, and I think much of the MPG-saving driving is engrained. I am not a PnG driver. I don't drive below the speed limit (though I rarely exceed it by more than 4-5 mph). I'm pretty consistent in the way I drive -- defensively and so as not to be in or cause traffic tie-ups. I do believe I've just left the A/C on more often, and I don't check the tire pressure as often.
• I've moved from 5,000 to 10,000 miles in between oil changes. In some respects, I thought this might help keep mileage higher. Even so, it is a change that happened at about 30,000 miles.
• I don't always use Mobil 1. I have used another brand's 0W20. Could this really be the cause of any change? Perhaps there are people who've done studies showing there is a cause and effect.
• I'm not the sole driver of the car anymore. Here is a REAL BIG reason for potential change. The reality, however, is that between my wife and my teenage daughter, they have not driven the Prius for more than a total of 600-700 miles. When they do, however, the mileage does tend to drop!
• I'm on the original factory tires. I do believe this is a factor in bringing the MID MPG readings closer to my actual measured MPG from tank fills. So this may account for some change, but I don't really know.
• The car has been hit three times -- hit hard enough to require several days worth of repairs each time. This really would be an issue, but all three times happened within a four month period during the first six months I owned the car. I don't see how this would account for an overall trend downward. (Actually, I believe MPGs increased after the repairs, only to decrease later.)

That does it. I don't know of other changes.

I'm attaching a graph showing three items charted against time. (I chose time, as opposed to miles, simply to show the seasonal effects on fuel economy in the Prius.) The first is the measured MPG from each fill-up. The second is a 2,000-mile trending of fuel economy. (This is a rather "rough" cut, but it accounts for the three or four most recent fill-ups.) The third is the lifetime MPG line which is the sum of all miles travelled divided by the total gallons of gas purchased. Notice how the 2,000-mile trend line acts as a good indicator of the seasonal mileage changes -- delayed slightly, of course.

If the .pdf of the graph isn't very clear, please take a look at the same graph posted in my photo album.