New car, slight MPG decrease after few months?

Fuel economy usually gets better as the car and tires break in. Unless you purchased the car right before winter....

Why mileage gets worse in winter | PriusChat

 

F8L posted what I was thinking. We are entering the time of year where a number of members who are new to the Prius will be posting up, wondering what happened to that fantastic summer MPG's they were used to getting.

I would ask the following

1) Have you clipped any curbs that may have tweaked your tire alignment?

2) Have you checked your tire pressures recently? If not, you may want to and you may want to inflate them closer to 40 than 33-35 PSI.

3) Has the weather gotten cooler? Significantly so?

4) Have the wind patterns in your area changed? Are the winds stronger? More cross winds or headwinds than before (look for flags on buildings along your commute to verify).

5) Have the traffic patterns in your commute changed? More congested maybe stop and go instead of slow and go?

 

Temps in the 90s+ are best for mpg depending on your AC usage. Once temps drop into the 60s I notice a drop and below 59F I notice a big drop. Rolling resistance decreases significantly in hot weather!

 

The temperatures you are in now are pretty ideal. You can get better mileage with temps in the 90's but if you use the A/C your mileage will decrease, so you are in a good time right now.

Your MPG's will decrease a little (~2 mpg) because winter blend gas is coming online.
Stop and go traffic is awful for any car, it is a little less awful for a Prius. Slow and go traffic is the Holy Grail of traffic patterns, because you have something of an opportunity to Pulse and Glide. However, it may be harder to do in the So. Cal Area because I suspect people are much more willing to "jump into your gap" because they may be able to get, exactly, one car length further along.

The real trick to pulsing and gliding in Slow and Go traffic is to avoid tailgating (not easy to do). You need to allow traffic in front of you to pull away (like extending an accordian), once they are well enough ahead, you give the car some acceleration (into the gas engine range....the second big fat bar) and gain speed. All the time you are looking for brake lights in front of you and gauging your closing speed on the car in front of you. As you start to overtake (speed wise) the car in front of you, let off the gas pedal and try to Glide (keeping the bar at the line between the regen braking and first fat bar, or just a little into the fat bar (all electric) area). If you time it right, you can glide up to the bumper of the car in front of you just as they are accelerating away (because traffic has opened up again in front of them).

A similar technique is called "driving without brakes". Same deal, accelerate (no tail gating) and try to modulate your speed by gliding or coasting (I equate coasting with no foot on the gas pedal and you have minor engine braking).

But still, even without this, you are beating 50 mpg, and just about every other driver this side of a Volt, Leaf, or Tesla would be jealous of that.

 

California also just went over to winter mix fuel (a bit sooner than normal), that may affect your mileage.

 

What about more frequent headlight use? That causes about a 5% hit on the EV range in my Volt which has conventional halogen headlights (as opposed to LEDs). Without headlights I get about 50-51 miles of range. The same drive with headlights is around 47-48 miles of EV range. I would guess it has a similar effect on gas mpg but I don't drive enough long commute segments on gas in order to validate that.

Does anyone know the effect of headlight use on Prius mpg?

 

Keep an eye out in the Fuel mileage forums. November is usually the beginning of the "Low Fuel Mileage Threads/Rants" season, which is why there is a sticky at the top of the forum.

Keep on keeping on!

Also, take a look at this link (it is my Fuelly page)

Codyroo (Toyota Prius) | Fuelly

Look at the fuel bars (tracked monthly) from Oct 11 - April 12 compared to May 12 - Oct 12. You'll see a big jump when the warm weather hits. Typically you may expect a 2 - 5 mpg drop during the winter/spring months due to temperature drops, rainy weather, windier weather, and different gasoline. But your hits in the So. Cal area will be much less that our less fortunate members in true cold weather states/areas. They really get hammered in the winter time.

 

routes do play a part in fuel mileage. I actually take a freeway exit one earlier than the most convenient exit to my house. This is because if I took the "normal" exit, I'd be driving uphill for about 1 mile, then as I exit off the freeway, I go down a steep hill and have to come to a stop at the end of the exit, in a valley. Now, from a dead stop, I have to go up a steep hill, where I can hit one of two lights that may potentially make me stop on an uphill. Once I crest the hill, I have a downhill with another light that I need to turn into my neighborhood. Lots of hilly driving and lots of lost momentum.

The current route I take is very flat (slight uphill, but long and gentle) and there are round abouts instead of stop signs. Any stop light I hit is on a flat road. This route allows me to conserve momentum almost all the time, and it is almost as fast.

 

To address the issue about MPG vigilance, I will agree this plays a large factor in actual MPG's. It's been said a lot of times, but it never hurts reiterating. The most powerful tool in your MPG arsenal is your foot!

I noticed when I first got my Prius I was extremely careful about my MPG, always accelerating in the "pulse" zone and gliding as much as possible. Now, sometimes I'm just tired from work and other things and am less vigilant (plus the new car excitement has worn off) so I notice a 2-3 mpg drop on average.

Also another note on MPG vigilance, when I'm talking on the phone (bluetooth of course) I tend to focus on the road more, less on my MPG's and notice a good 5-10 mpg hit. From your posts with your MPG jumping back up into the 55-60 range I'm guessing your attention to it has brought it back up to what you were used to seeing

 

My last tank was 45.9 mpg calculated. Now with wet winter weather with temps in the 40's to low 50's
my true calculated mpg's will be 44-48 mpg.

Last month 52-54 mpg calculated was the norm...

Prius loves summer, hates winter......