Driving for efficiency

Somebody thought it would be a good idea to form clubs: 600 miles, 700 miles e.t.c. It appeared to be open to all Prius models so I thought to share what an older Prius can accomplish with just efficient driving. But in reality, I'm interested in sharing what our model Prius can accomplish so I've copied my posts to this thread.

A 2003 Prius with 150,000 miles, a work in progress, this photo was about an hour old:

The tank bar is NOT flashing. When it flashes, I typically have 1.2 gallons or about 70 miles remaining. When it starts flashing, I'll carry a 1 gallon spare in the trunk and run it dry. BTW, this is Costco, regular, E10, ~$3.17/gallon.

So this is what the mileage display showed:

BTW, the mileage and miles are ~6% low. The true miles are ~636 miles. I've checked the calibration against both GPS and highway mile markers.

The front tires are ~6% larger diameter than the stock tires, notice the difference in the side walls in the photo:

The tires are described here and consist of:

• Front - Sumitomo T4 195/70R14, 849 rev/mile vs 902 rev/mile stock, improved straight-line stability, probably due to gyroscopic forces. The 6% over-drive effect means the transaxle turns slower, lower stirring losses at equivalent speeds and distances. Also using Type WS transaxle oil instead of Type T-IV, the original.
• Rear - Sumitomo T4 175/70R14, 886 rev/mile vs 902 rev/mile stock

My vanity plate:

Yes, that is a trailer hitch.

Driving style:

1. Select routes where the posted speed limit allows 40 mph or lower without bothering normal traffic flow. Less traveled is better, avoid the crowd.
2. Follow the slowest traffic: DO NOT TAILGATE!! EVER!!! NO DRAFTING!!!!
3. Change lanes to let over-taking traffic pass on whatever side they want.
4. 0-50 seconds - accelerate modestly on traction battery to ~38 mph, shift into "N". This is when the catalytic converters are warming up and the control laws try to minimize ICE power by using traction battery energy.
5. 50 seconds -> 70C coolant - slowest speed the traffic allows (25-35 mph), choose downgrade routes, and use "N" when practical.
6. 70C - seek opportunity to go Stage-4 (i.e., stop and let engine auto-stop).
7. Use cruise control to hold speed.
8. Choose two lanes or more in your direction over one lane to let faster traffic pass.
9. Choose flatter routes over hills and grades.
10. Choose fewer stop light routes unless stop light timing for "green just in time" speed is known.
11. Make first leg of multi-stop trip the longest.
12. If the choice exists, accelerate on downgrades and approach stop lights on upgrades.
13. Try to keep ICE rpm < 2,400 rpm but don't make a fetish out of it . . . avoid accidents.

There is a reasonable probability that I'll reach 700 miles indicated on this tank. Another 75 miles and the true miles will be 700 miles. Without 'flash', I'm 75% sure I have enough gas for true 700 miles and about 25% confident I'll reach 700 miles indicated.

Bob Wilson

ps. The reason we do not tailgate or draft or follow closely is the leading vehicle speed changes often means touching the brake to avoid a collision. Worse, trying to accelerate in sync wastes gas. We want to minimize braking and throttle. Even regenerative braking loses some energy that can never be reclaimed. Throttle simply wastes gas as we're trying to get somewhere efficiently, not do some sort of 'formation driving.' At these speeds, aerodynamic drag is insignificant compared to inertial, speed change losses.

pps. We kept driving on that tank:

Our 2003 Prius:

GPS corrected: ~752 miles.


GPS corrected, flash distance: 112 miles. I had a spare gallon in the trunk.


GPS corrected miles: ~752 miles due to oversized front tires.


Curious, I've never filled it with 12.2 gallons before. Usually 11.7 has been the best.

 

No problem:

We bought it in 2006 from Coastal Electronic in Florida. Once it arrived, I removed the rear tie-downs and bolted it on using permanent Loctite and a torque wrench.

Another Prius owner had his own built: John's Stuff - Toyota Prius Receiver-Hitch

Bob Wilson

 

Inserted

* * * Comments * * *
What are you using to get the temp measurement reading for the ICE? and how are you measuring rpm speed, to keep it under 2400rpm?

Graham Miniscanner but I could also use a ScanGauge for the metrics. As for 2,400 rpm, each OBD scanner report four metrics and I set one to ICE rpm.

I just finished getting the highest tank yet at 574 miles until warning light.

"Warning light?" Do you mean 'flashing fuel level indicator?' In my car, I've measured 1.2 gallons remaining before finally out of gas.

Any tips for highway driving? I try to keep it under 62mph on a section of 4 miles of highway driving.

My metrics show 65 mph is the sweet spot, 52 MPG if the car is optimized. At 70 mph, it drops to 49 MPG and 75 mph, 39 MPG. Stay at 65 mph and you'll be good to go.

Are there any sites that show the elevations of roads for best route planning?

Google Earth has that function. You'll have to map a "path" but then you can view elevation.

* * * End comments * * *

Good luck, drive safe, and courteous,

Bob Wilson