After 4 years, I am finally getting good mileage ...

**Warning - Long Post**

I had a Gen II 2006 Prius and over its 3-year lifetime, it was only averaging 43 mpg. It started out higher because I was driving longer distances. It did have a couple of 50+ mpg tanks, but that was only when I was on a road trip. When I bought my Gen III in 2009, I had heard all the hype and was hoping to see much better results, so was disappointed when I didn't do any better.

I tracked my mileage for the first 30 months and my lifetime average came to just over 43 - the same as the previous Prius. Most of my tanks were in the mid-40s, with only a couple reaching 50 or more, and several as low as mid-30s. My low overall mileage was because during the week I was driving just a few miles a day to get to the Metro station and back and the engine barely had a chance to ever warm up. Also, where I live, there are a lot of stop signs, traffic lights, hills, and traffic.

Two months ago I changed my job location and am now driving 52-54 miles each way to work. It's a very hilly ride, with 90% highway at 55 or 65 mph. My usual speed is between 61-67 mph. Since starting the new job, I started tracking my mileage again. At first I was getting around 47 mpg at fill-up but now I am consistently getting 50+ mpg tanks (calculated). Now that I have a consistent 100+ mile daily commute I can track the factors that seem to make a difference.

1) Energy Saver Tires: When I was first getting the 47 mpg tanks, I was driving on the OEM Yoko tires. I bought some Michelin Primacy tires and my mileage immediately dropped to around 43 mpg on the first fill-up! On the second fill-up it went up to around 45 mpg, but after 1000 miles I decided to exchange them for the Michelin Energy Saver All Seasons. My mileage immediately went back up to 48 on the first tank.

2) Weather: Mileage dropped a bit on second tank because of rainy conditions. However, I have since driven in the rain and have maintained high mileage.

3) Using Cruise Control: Again, my route is extremely hilly. I am going up and down hill all the way. I have tried the DWL technique and it just doesn't work for me. Although traffic isn't heavy, there are always cars behind me and everybody drives above the speed limit. And even if there aren't any cars, some uphill climbs are really long and I would find myself slowing down way too much and having to gun it to get back up to a decent speed. I have found that using cruise control to maintain as constant speed as possible gives me the best results. Even when I set the CC fairly high - 66-69 mph - I do much better than when I'm constantly speeding up and slowing down to compensate for hills and traffic.

4) Distance, stop-and-go, and hills: Normally, my mpg readout does not reach the mid-40s until I've gone about 10 miles. Then it reaches the 50s at around 15-20 miles. There are several factors - from my house to the highway, there are 6-9 traffic signals (depending on which route I take) and most of them turn red. (I think my Prius has a red-light triggering device built into it ) It is also very hilly. So between the stop lights, traffic, and hills, the first few miles are mileage killers for my poor little Prius. My mpg readout reaches its highest point about 30 miles into my trip. On the way TO work it sometimes gets as high as 60 mpg. However, a few miles before I reach work the speed limit slows to 45, there's a light at the bottom of a hill, and the speed limit goes up to 60. Over the last few miles my mpg readout drops about 3 mpg. I make up 1 mpg on the final 1/2-mile leg.

5) No-ethanol gas: Okay, I've only filled up for the second time today on zero-ethanol gas so I can't say for sure. I only put in 6 gallons on the last fill-up, so my tank was not completely ethanol-free, but my calculated mileage on today's fill-up was 51.3 mpg, which is one of the highest tanks I've had. The next time I fill up, I would have been using a 100% ethanol-free tank. I found this gas at a Liberty station in Charles Town, WV, which is a few miles from where I work. There is no ethanol-free gas anywhere near where I live (Washington DC metro area).

6) Normal, ECO, or PWR mode: I don't think it makes any difference at all. I usually have it on PWR mode while I'm on secondary roads because it's much easier to get up the hills from stops. Sometimes it's on the whole time and I see no drop in mileage. I can't stand ECO mode if I need to get up to speed or pass - it feels so sluggish.

My point for writing all this: if anybody is disappointed with the mileage they are getting, it is very likely due to the driving conditions rather than poor technique or something being wrong with the car. The biggest mileage killers are:

• Short trips
• Stop-and-go (red lights, heavy traffic, etc.)
• Hills and curves
• Bad weather
• Excessive acceleration and braking

 

You are right, of course, but my reason for this post is for those people, including me, who bemoan the fact that their stats never seem to live up to the 50-60 mpg per tank that others in this forum are reporting.

And I also never understood the EPA estimates that give equal or better mileage for city driving than for highway. At least in my case, city driving means many short trips and stop and go due to lights, traffic, and turns. What do they consider "city"?

 

when you say you get 60-65, are you talking about the mpg instantaneous readout or the calculated average for the tank? Yes, I can get 100 mpg in some cases, but when my driving consists of only short, start-and-stop trips, my calculated average on fill-up is in the low 4os at best.

 

It does seem that other people's experience with city driving is different from mine. But in my case, too, I am not talking about 10-mile trips at a time, but maybe 1-5 miles. It could also be because of the hills around here. If I'm stopped at a light at the bottom of a hill, then I have to use energy to start up again. All I'm saying is that after 7 years of driving two different Prii, I have not been able to exceed the mid 40s average mpg while I'm doing short commutes around town. When I look at other people's stats on Fuelly, mid 40s isn't that unusual.

 

Since I got my new tires and my new commute, I've been regularly tracking each trip by resetting the B odometer. On my 52-mile trip to work, my mpg readings upon arrival are 52-57 mpg. For my trip home, they are 53-60. If I go out for lunch, a 10-12 mile round trip (with a stop for lunch), my trip averages have been in 39-45 mph. The main road where I work is a 60-mph divided highway - but there are several traffic lights. And it's very hilly. So there is a lot of slowing down and accelerating from a stop or to climb a hill.

I've also noticed that when I first start out and I'm getting a really low mpg readout, it's much better if I speed up quickly (using the PWR mode).

 

What are your average trip distance, topography, and traffic conditions? Is 55.5 mpg your calculated tank average or displayed average?

 

I raised psi to approximately 38/36 shortly after the new tires were installed but haven't checked recently. (Checking tire pressure is one of the chores I'm not too fond of.) Next time, I'll try raising it to around 40.

Regarding speed limits - in this area, nobody drives at the 55 mph posted limit. One has to be going at least 60 in order to keep up with the flow. Even if I'm driving 63/64, there are people whizzing by or coming up rapidly on my rear. At 65 mph, most people are around that speed. Not many drive too much faster probably because there are a lot of hills and curves and the lanes are narrower in some stretches so it can get pretty hairy going very fast.

 

I generally don't like to drive in the rightmost lane because one constantly has to change speed to allow for traffic merging in from the exits.

Speaking of trucks... one day there was a large truck riding on my tail for a long time. I wasn't in the leftmost lane and I couldn't get into the lane to the right because of traffic. Finally I did manage to get over to the right, hoping to lose him. Guess what, he got in right behind me. I changed lanes again, and he got behind me again!! I managed to lose him finally but I was getting so annoyed. I don't know why he kept doing that. I hate it when people tailgate me, especially a large truck. But I also don't like getting stuck behind a truck because I want to be able to see the road ahead.