Using mostly battery less than 40mph

How does your car map in this chart?

The protocol:

• find a flat section about 10 miles in length and drive 10-20 minutes to warm-up car
  • accelerate to a target speed and set cruise control
  • reset trip meter
  • at end, record MPG
• turn around and repeat the test
• average the results.

Bob Wilson

 

I have had my Prius for about 3 months now and have already driven it almost 10,000 miles. I have driven in about all situation, except winter driving.
Here are the things I have learned about improving gas mileage.
1. Use the HSI screen that shows how hard you are pressing on the accelertor. Avoid going more than halfway into the PWR range or more than halfway into the reg charging range, except when necessary.
2. Get a device like a Scan Gauge II. Use it to monitor your Engine Water Temperature, RPMs, Engine Timing, and Instantaneous MPG.
3. After starting the car use a very light pressure on the accelorator until the Engine timing goes from reading negative to a positive number. This typically occurs around water temp of 103degF. The timing will likely go from like -5 to 15. Then still only accelerate lightly until the engine temp gets up to 155degF. At that point the timing should go in the mid teens to mid 20s and even up to 33. Once the timing gets above 20 you can drive it like a normal car. However when accelerating or going up hills try to keep the ignition timing above 27. With heavy throttle it will need to make the fuel mixer richer and retard the timing which uses more fuel. This applies to when the Instantanous MPG is in the 30 MPG or lower. Don't worry about the ignition timing when the Insantanous MPG is above 40 MPG because I think the system also retards the timing when its running a lean mixture and taking advantage of the variable valve timing.
3. I try to avoid reg braking. I will instead try to "coast" with the throttle showing neither reg or EV usage. There are energy losses for using EV and charging the battery from both the ICE and reg braking. All the energy, including losses must come from the ICE and gasoline so avoiding those losses will help MPG. However the BIGGEST energy loss is braking beyond the reg braking bar being maximum to the left. Hard braking turns the momentum into heat in the mechanical brakes. On a couple of recent trip to Chicago I was surprised I much I was able to avoid hard braking even in heavy traffic.
4. Out on the highway I use the Cruse Control, not necessary for MPG, just because there does come of time to just drive and be comfortable.
5. I only use E10 every other tank full. Back to back tanks of E10 usually puts me below 50 MPG. If mid tank I am below 50 MPG I will top off with E10 which has always returned my MPG to 50+.

By driving like I described above I have increased my 20 mile drive to my parents from 40 MPG to 52 MPG and my 35 mile commute to work from 52 MPG to 55 MPG.

Light throttle during the warm up time and limiting the usage of E10 has made the biggest difference.

I just got back from a 390 mile trip to and from Chicago. HSI says I got 54.9 MPG with AVG 51 MPH. I was doing an average 70 MPG on the interstate. Now the HSI is typically about 2.5 MPG high, but I am still happy.

Good luck. I hope you are able to improve your gas mileage and are happy with your Prius. It unlikely I will every purchase a non-hybrid car again, at least for normal driving.

 

It just takes practice to figure out what techniques work best for you in different situations. Even if you only add a couple glides at key points, it'll still help. Your tires are probably knocking a couple MPGs off, so you have to factor that in when comparing yourself to others.

 

This was an evening commute of 17 miles. Going from left to right;

Around the 30 min section I was slowly accelerating and coasting to red lights (P&G whenever possible) for a readout of 75mpg.

Then for 25, 20, and 15 min sections I had cruise control set to 55 mph on the freeway (3/4 the trip) and netted above 50 mpg consistently.

The 10 min section was going uphill on a decent grade and the 5 min. section was going uphill on a VERY steep incline. All-in-all, on these Micheline Energy Saver tires I get better mpg everywhere on my trip.



I would say with a touch of caution these numbers are realistic to reach. Be advised that the on-board report inflated actually mpg by a figure of 1-2 mpg across the board though.

 

The engine can't charge the battery if it is not running. There is some charging done during the pulse up, but it is minimal. Almost all charging is done by the regen systems. Keep in mind, this is for surface road driving with the accompanying regen opportunities. For highway driving, the best way to increase mileage is to slow down...which is not always a safe choice. The difference for me between 60 and 70mph is the difference between 55 and 65mpg.

 

the engine runs every time you pulse.

 

goota get those energy saver's man!

 

Two very basic things I take away from Bob's (much appreciated) chart: speed's hard on mileage, and the in-dash display of mileage is VERY consistently wrong, always on the same side.

 

What I failed to do was to measure the calibration offset of the OEM tires. A strange blind-spot because I had been running oversized front tires on our 2003 Prius, 6% larger diameter. After my recent marathon, I realized the indicated miles and MPG gives accurate fuel consumption. It is the miles that are off due to tire diameter.

Bob Wilson