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Old 06-27-2011, 07:24 PM   #2 (permalink)
bwilson4web
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Quote:
Originally Posted by Jesse View Post
I just bought a 2005 Prius with 73k on the odo, it has Nexen CP641 non LRR tires. I have an ecomodded civic si that could get 50mpg with proper driving techniques.

My first tank with the Prius was only 52.5 mpg. No ecomods. I rarely used air conditioning, and stayed under 70mph, usually went 60 to 65. Had some rush hour congestion. My current tank I am only averaging 49.9mpg, staying under 60mph. Think these tires really could be costing me that much mpg?
We can't tell and if the tires look good, it may be a while before you put on some LLR tires. But let me suggest some things to consider:
  1. Benchmark the car - without making any changes, find a relatively flat, 10 mile or longer section, and run bi-directional, mph vs MPG runs, after warming up the car for 20 minutes. It doesn't have to be the same 10 mile stretch but capture: 30 mph, 40 mph, 45 mph, 50 mph, 60 mph, 65 mph, 70 mph, 80 mph (some subset.) At 41-42 mph (indicated,) the car goes from hybrid mode when it can turn off the engine to non-hybrid mode when the engine always has to turn. BTW, data from more than one Prius owner has suggested 65 mph is an optimum cruise speed.
  2. Change one thing at a time - re-run one or more of the benchmark speed runs. Be sure and record the ambient temperature and if you have the option, stay in 60-70F region.
Things to investigate:
  • oil level - many of us believe it should be 1/4 inch below the "F" and NEVER over "F".
  • tire pressure - find the maximum sidewall pressure on the tires and set them to it.
  • temperature effects - select one or more benchmarks to repeat at 20F, 30F, 40F, 50F, 60F, 70F, 80F, 90F . . . Or what ever termperature ranges you want.

Quote:
Originally Posted by Jesse View Post
On Priuschat most owners who drive this slow achieve about 55-60mpg easy.
You may want to consider recording your fill-ups at:
  • Ecomodder.com - Oh, here it is. <GRINS>
  • MyHybridCar.com - a large collection of Prius and other hybrid mileage records.
  • Fuel Economy - a US Government web site that is unlikely to go away or be bought.
  • fuelly.com - another open web site for recording mileage.
I know how strong is the desire to do a whole bunch of stuff early without taking the time to keep careful records. The risk is you might develop a 'superstition' that some arrangement of dangling fuzzy dice and sunglasses always gives great mileage (knock on the dash three times and say one "Hail Exxon.')

You are going to be with this car for a long time, patience and you will let the car teach you what works or doesn't work. Then you'll know and be as smugly self-confident as . . . <GRINS>

Let me share some examples:

This is my first mph vs MPG chart started on the flight out to pickup our 2003 Prius and then the segments on the highway back. Notice the oil level experiment and the effect of cold weather. It also includes two sets of NHW20 (your model) Prius data at high speeds.

Treat everything as an experiment including your commuting route:

Using Google MAPs, I loaded a PowerPoint chart and plotted every practical route to and from work. Then using weekly gas fill-ups, I tested each route to find out what works and what doesn't. By weekly fill-ups, I filled the car Friday evening and Sunday evening. This kept my weekly commuting data separate from the weekend fun drives.

Again, be patient as you're going to have this car for a long time. So run the experiments, keep and more importantly, share the results ... especially here.

GOOD LUCK!
Bob Wilson
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2019 Tesla Model 3 Std. Range Plus - 215 mi EV
2017 BMW i3-REx - 106 mi EV, 88 mi mid-grade
Retired engineer, Huntsville, AL
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Jesse (06-28-2011)