When Will My Mpg Improve On My New Prius

An optomistic note to fellow newbies --

Have had 2008 Prius 6 weeks & 900 miles.
Kept to the basic PriusChat suggestions:

• Upped the tires to 42/40
• Pulse/glide as much as possible
• Do the no-arrow coast whenever I can

(Also -- I turn off heater at lights, otherwise, ICE runs)

3 tanks in 30-40-degree temps:
1. (dealer tank) -- 38 mpg
2. 42 mpg
3. 48 mpg

Can only get better !

 

I've actually gone to never having the climate control on at all. Sounds extreme, but it hasn't been too bad. It's been hovering around 40 degrees here, and I've got a coat on. Definitely manageable, and I'm sure it kicks me up 1-2 mpg.

 

My observation @ 0 (f), no block heater, no grill blocking, 5,000 miles since the end of November.

Driving less than 10 miles gets me about 25 mpg
10-25 miles gets me about 35 average
20-40 miles gets me about 40

@ 20 (f) add about 4 mpg to the 0(f) figures

@ 40 (f) add about 6 mpg to the 0(f) figures

In a nut shell Winter sucks. Between the winter blend of fuel (good for a 10% loss) and the cold weather, mileage will suffer.

 

You do realize you're not putting 11.9 gallons into the car on each fill-up, right? Even under the best of circumstances, you might be putting 11.5 gal and in the winter when the bladder doesn't expand as much, it might only be 10 gal.

You're correct about not wanting to run out of gas, but you should also not try to force 11.9 gallons into the tank when it won't fit or bad things happen. Expensive bad things. (It sounds like you have some experience with the Prius and know not to do this, but I'm not sure if some readers of your post might misinterpret what you're saying).

Not sure I'm following this. If you drive for 400 miles easy and light, then drive 150 miles aggressively, you should get the same result. I think it is averaging it correctly, you just might be surprised how much it affects the average.
Let's say you drive 150 miles at 30mpg, and 150 miles at 50 mpg. You might think the average is halfway between the two: (30+50)/2 = 40mpg. But the answer is actually 37.5 mpg. The first 150 miles take 5 gallons, the next 150 takes 3 gallons, so you have 300 miles/8 gal.

That is exactly correct. Gentle hills at 40 mph is another good scenario (using pulse-and-glide).

Short trips are bad, cold weather is bad. These are the two biggest factors for mileage (can affect it 30 - 50%, I'd say). After that, pumping up the tires beyond the recommended minimum will help, coasting to stop lights, blocking the grill in cold weather, etc. will each help 10% or so, depending on situations.

Umm, not entirely the best scenario for best gas mileage. The battery gets its power from the engine. Better to use the power directly if you can. The engine is most efficient when running at about 75% capacity, which is an acceptable acceleration, not pulling power from the battery or adding to it.

Think of it this way:
engine->wheels
versus your slow electric-only acceleration from the battery:
engine->wheels->regen braking->battery->motor->wheels, or
engine->generator->battery->motor->wheels

The battery is to help accelerate when needed, so a smaller, more efficient engine can be used in the car without leaving it underpowered. And it runs the A/C and controls and such so the engine can safely turn off when not needed.

Some of us think it is fun, to beat your last high score. But you're right, it is a sensitive system and if you really needed to, you can get some incredible mileage from it. Some people have gone 1000 miles on one tank (under optimum situations).

But for some numbers: my current 3-mile commute in cold weather and sometimes slushy/snowy roads gave me 38 mpg (I was down to 33 mpg before some longer trips in (barely) above-freezing temps). However, my lifetime average is about 49.5 mpg (had my car almost exactly 2 years now), and in summer I've gone on trips where the 3-tank average is 57 mpg. (Because of the vagaries of each fill-up, I tend to go with the 3-tank average as being a truer value).

Yes, I realize a 3-mile commute is ridiculously small. I try to get my wife to switch cars since she has a longer commute, but emotional attachments over-ride common sense. And in the months where the shoulder of the road isn't buried in snowdrifts and the sun stays up after 5 pm, I ride my bike.

 

The temperature does affect MPG, but not as much as some of you are stating. The direct affect is to lower MPG by about 10 % (eg. from 46 to 42). Any lower MPG is usually due to one of several causes:

1. Low tire air pressure - when the temperature drops, so does the PSI in your tires. Get them back up to at least the suggested 35 front and 33 rear (I run 42/40 to get better MPG - stay below the MAX cold PSI tire rating on the sidewalls).
2. Short trips - your Prius needs to fully warm up before you will see 45 to 46 MPG (or 42 in the winter). This can take up to 15 minutes of driving in cold weather. Until then you will average in the 30's (increasing over the first 15 minutes).
3. One other small factor is an overfill of engine oil. Check the oil dipstick to ensure that the level is just below full (not over).

JeffD

PS. there are tires that will slightly increase your MPG ( other tires can cause a 5% decrease). I am currently running Nokian WR tires and see about a 1 MPG improvement - especially in cold weather.

 

thanks for the info

is the 42/40 I keep hearing about appropriate for stock tires on an '08?

btw...I'm up to 600 miles and my average mpg is much better...~50

 

Assuming you have the stock GY Integrity tires, max cold pressure is 44 psi. Check on the sidewall of the tire. You can safely inflate to any pressure at or below the max cold pressure.

 

thank you

and is the general concensus that the front is two pounds higher than the rear no matter what pressure you're running?

 

Toyota recommends two psi higher in the front because of front/rear weight distribution. However, I have also run 38 psi front and 38 psi rear and I really couldn't tell much difference between 40 / 38. I usually run 40 F / 38 R.

Lots and lots of threads (and opinions) on tire inflation.

 

We're in Nebraska so I know how you feel! 31 is what I'd been averaging and that's with us having an EBH so I finally got tired of that and blocked the grill to see how that would help and now we're at 41. My DH gets better mpg than I do but I'm happy with 41 for the winter! I'd block your grill and bet you see some improvement!!

 

I'm envious. I can't break 40, even though I've: Inflated to 42/40, blocked grill, use P&G, changed some routes and I've got 2000 miles on the car.

Guess the problem is the predominance of short, suburban trips up steep hills to drive kids to school and activities. Well, that brings up a technique I haven't tried yet - dump the kids!

 

the steep hills are probably the culprit. I live in shadyside and commute downtown so it's totally flat. When I go up and over Squirrel Hill my mpg struggles.

 

Your commute is a good one for mpg's - lucky you.

 

Maybe you could have the kids get out and push. :bounce:

 

I'm doing a 52 mile one way commute in the DC area and getting 54.1 mpg overall. I'm really driving differently in my Prius than my old car. Lots of gliding and slow accels.

Yeah!!! :hippie:

 

As for voiding the warranty,,,, The dealer will never know. All you have to do is stuff pipe insulation in the grill slats and take them out when (if) you go to the dealer for service. There is ample evidence on this forum and elsewhere that there is no risk of damage to any part of the car if you keep at least the bottom slit clear, and reduce the number covered above ~50f. Scan gauge as well as Can-gauge users can confirm this.

The car is built to withstand extremes of heat and cold, but operates most efficiently when the coolant is ~190f. I can tell you, that it takes ~20 miles of 55mph driving with all the slits blocked (except the bottom one) for the temp to get to 190f. This with an outside temp ~40. I garantee you will NEVER get there ~-10f.

Those of us up north have been driving cars with "winter fronts" (grill blocks) for years.

Block the grill and don't worry about your dealer. Even if something goes wrong he can't prove that you did anything wrong.

Icarus

 

The principles:
The engine is most efficient at high load.
Gliding (no arrows) is better than coasting.
Coasting is better than braking.
Braking is better than coming to a stop.

Ideally one would floor the gas pedal until reaching a speed which allows one to glide to a stop at one's destination. Obviously this is impossible in almost every realistic situation, but the closer you can get to it (between stop lights, for example) the better your fuel economy will be.

 

I have heard this to, many times. My question has always been, why is gliding with no arrows better than gliding with arrows to the battery? I am sure that the car doesn’t slow significantly faster just because the car is using your inertia to re-charge the battery. I would also think that in the long run, having a more charged battery from coasting with the arrows would help because the ICE would have to work less at the next acceleration. Does that make sense?

 

Stopping is better than running into something. :yo:

 

This is getting into the hypermiler territory, but the principle is that whenever you are adding or subtracting energy from the battery, there are conversion losses. So, if you can avoid the conversion losses, there is more energy available for moving the car down the road.