Need help getting better MPG

What tire pressures are you running?

The Prius, IIRC, has a suggested pressure of 35 psi front and 33 psi rear. Many Pris drivers increase that, sometimes quite a bit. I run 40 front/38 rear.

When I added more air, I noticed two immediate effects: An increase in gas milage and an improvement in handling. The car now wallows less and handles more crisply.

I also notice that the traction control system activates more easily, but I have never felt unsafe or in danger of losing control when this happens.

 

Start with this.

Who p***ed you off in the CleanMPG article and why?

Increasing tire pressure above "standard" (i.e., placard) pressures will indeed improve your fuel economy. If you're going to request advice, you might consider heeding it.

 

LOL, that was me that you got pissed off at.
I think the main culprit is your short commute. At 7.5 miles each way, the car barely has time to get warmed up by the time you are at your destination.

 

I am certainly no expert (1900 miles on my G3, IV), but I agree with the above comment. Is the drive to and from work the only time you drive the vehicle? That will be tough!

I suggest you monitor the Hybrid System Indicator (HSI) screen. Make every effort to keep the "ECO" light on. The sliding illuminated bar wants to be to the left of center as much as possible, however, it can go to the right of center, and as long as the ECO light it lit, you will be doing OK. Avoid being all the way to the right .... PWR.
Make every effort to drive steady. Accelerate with the flow, but try to avoid speeding up, changing lanes, slamming on the brakes (I know, I have driven in Houston).

The HSI screen will also give you an indication of how your fuel economy is doing. Once the engine is warm, driving a steady 35-45 mph, the scale should be well over 50 mpg. Then as you get off the accelerator and coast, it should read 100 mpg. At a dead stop, it obviously reads 0 mpg. It's OK for it to read 25 mpg when accelerating, but as you stay with the flow of traffic, it certainly should be well above 50 mpg. You just need to drive sufficient miles in that mode for the average to improve.

Houston is a tough driving environment. My Sister lives there, and I ask her ... why do you live here?

Good luck. I think the Prius requires some time to "learn" how to drive it economically. Go for a Sunday drive down to Galveston. If you drive steady on the Gulf Freeway, you should get 52-53 mpg. Then drive to the West down the seawall drive at 35-45 mph and you will approach 55 mpg. I am convinced it is not necessarily slow driving, but steady driving that is important.

 

Houston through summer will be tough on mileage due to AC use and Houston traffic (used to live there.) With a short commute if you have the AC blasting you are going to lose a lot, particularly at low speeds or when stopped. I try to run the AC on low blower settings, and only when I need it. This keeps the ICE off for short stops/at lights. Houston has two advantages: very mild winter, plus it is flat.

I run 42/40 on my pressures, this is within the sidewall rating and seems to work better with the tires than the placard pressure.

City street speeds of sub 35 mph are ideal for pulse and glide IF you don't have to stop or brake alot. You want to keep the car from regenning as much as possible (as it does when you are completely off of the accelerator) as well as avoiding doing extended yellow arrow EV drives. Drive like you don't have brakes, do regular ICE acceleration and learn how to do the "no arrow" glide. While the Prius mpg peaks somewhere around 20 mph that is without the AC on...with the AC I suspect the peak is closer to 30 mph depending on settings.

I change my own oil and use 3 quarts instead of the nearly 4 quarts that Toyota lists (which results in an overfill condition.) Some have observed mpg reduction with the standard Toyota overfill quantity. Have you checked your oil level?

For acceleration the target is instantaneous mpg of ~1/2 of your speed. This gets you into an efficient operating zone. Too low of an acceleration is actually detrimental to mileage, as is flooring it.

Make sure your car tracks true. If it is pulling to one side or another then you will lose gas mileage and need an alignment (free within the first year or so.)

The 7.5 mile commute is better than the 6 mile commute our Prius regularly sees and its getting 54 mpg on the current tank, despite hills, many stops (mostly at the bottom of the hill, arggg), and highway intermixed. At 60-65 mph, you should be seeing about 55-60 mpg while cruising, but on short commutes this will be seriously derated for warm up and initial acceleration.

It takes awhile to break in the car, tires, and driver.

 

Do you reset the average for each tank? If you don't, it may take a while -- perhaps a long while -- to see any changes.

 

No problem, I took it as such.

 

I don't think a short commute always means less mileage. My commute is 5.7 miles each way and I am averaging right at 53 mpg. I was in 46-47 range until I became a pulse and glide convert. I also changed my route to residential neighborhoods with very few stops and a 30 mph speed limit. My experience (which is limited at this point) on highways is that once your get to 65 or over the mileage does back off some. If you are doing stop and go on a highway, meaning stoping and than getting back to 65 and than stopping agian, that would kill your mileage. One thing to keep in mind, regardless of your mileage in your Prius, it is probably 2-3 times what you were getting in your previous ride.

Kirk

 

A short commute for one person is not necessarily a short commute for another. e.g. your 5.7 mile commute at 30 mph gives the engine a bit of time to warm up. However, the same distance on a hwy means the engine has less time to warm up (granted, it is pushed harder/hotter on the hwy).

 

Short path economy zen:

Accelerate briskly. If everyone else passes you when pulling away from a stop you're doing it too slowly, and thus not using the engine very efficiently.
Gliding (no arrows on the "Energy" display) is better than coasting
Coasting is better than braking
Braking is better than stopping
Doing the above three without becoming a victim of road rage is a challenge.

Do Not use "B" in normal driving. There's no place within about 500 miles of Houston where it is needed.

Make certain that the battery system vent next to the rear seat is never blocked. And *do* use the air conditioner, because if you're too hot then the battery system is also too hot.

42/40 PSI front/rear in the tires will help. Check pressures at least monthly.

 

Buy a scan gauge, and plug your grill. Even in Houston cold starts, and short trips will make it hard to ever get to operating temps. I drive with the top grill 3/4 blocked all the time, the bottom 100% block when the ambient is below ~60f. We get ~52 mpg on average. Scan gauge reveals temps have never gotten over 205F in the heat of summer, (last week was nearly 100f) and the A/C going. Normally it struggles to get to 185, where the T-stat BEGINS to open.

PLUG THE GRILL!

Icarus

 

I have seen this repeated many times but after driving for some time now I wonder how true it is. Whenever I accelerate with higher RPM the instantaneous MPG bar on the MFD always drops lower. I don't know how the efficiency of the engine is measured but after all it is MPG that counts I think. If there is data showing higher RPM giving better MPG I would love to see it. Thanks!

 

Do you block the center 3/4 or the two sides (leaving the center open)? Thanks!

 

Confused +1

The brisk acceleration advice to my mind has always conflicted with the 1/2 MPG to MPH rule (although I do wonder whether I am doing it correctly) as the latter seems to require very gentle acceleration?

 

Any car gets better gas mileage cruising at speed than it does accelerating. To maximize time spent cruising, you want to minimize time spent accelerating (within reason). To spend less time, you need to accelerate quicker.

In a gasoline engine, the throttle plate can cause restrictions in the air flow, larger throttle openings have fewer air friction losses. (at some throttle opening, often full throttle, most gas engines choose a richer gas to air mixture, this will offset air friction losses)

 

I don't care much for subjective terms like "brisk," "moderate," or "gentle." What is moderate to one person may be either brisk or gentle to others.

Instead, I promote the 1/2 MPG to MPH rule for acceleration -- i.e., keeping iMPG at least half the vehicle speed. That, BTW, is not what I call brisk. I agree with Richard that if everyone passes it's not brisk. I disagree that to let everyone pass you is inefficient. As much lead as others seem to have in their right foot, it might be inefficient to keep up with them!

The subject of how much go-pedal to give during ICE-on conditions is a matter of substantial discussion. Low-RPM conditions are thought by many to be inefficient, and the theoretical power curves of the Prius ICE seem to confirm this. But anecdotally, I and other hypermilers have reported good results with keeping RPM as low as 1200 or 1300. That pushes the iMPG well above vehicle speed, perhaps up to x1.5. It also is gentle acceleration by anyone's definition. Most assuredly, virtually every other car will be passing.

I have done some preliminary testing comparing various acceleration rates during pulse and glide, and the results suggest that rates in the range of 1300 are at least as efficient fuel economy-wise as those in higher ranges. The key word is preliminary, however; the test environment was less than ideal (traffic disrupted my glides on the two-lane rural road I was using), and I'd like to repeat the tests in a different environment.

Meanwhile, Hobbit has experimented using fuel injector timing as a surrogate indicator of engine load. The ICE really is inefficient when it's not running under load, and his view seems to be that as long as injector timing has reached a certain operational plateau, the ICE is loaded. Quoting him:

"Even a fairly gentle startoff from the line yields injector times of high sixes or 7.x at ridiculously low RPMs like 1250, as high torque is produced to help takeoff."
​

My own recent experience applying this and using injector timing as my load criterion (monitored in CAN-View) suggests that in ICE-on conditions at low speeds it's actually difficult for the ICE not to be under load. Especially from a dead start, after "goosing" the go-pedal just enough for the ICE to light, I show injector timing levels well above the "loaded" threshold even with these low RPM.

Therefore, it seems the iMPG can be well above MPH with the ICE still under load and, therefore, the car accelerating efficiently.