Are all Prii created unequal?

[j4wendling]

My wife and I bought used cars in October--I have the ‘04 Prius and she has the salvage title ‘03 Civic Hybrid. She’s beating my mileage at times! I’m only getting about 37 now, with cold, lots of stops, and short commutes to work (6 miles.) It doesn’t seem to matter too much how carefully I drive (I’ve read the posts and employed all the tricks I can.) Now here’s another kicker: a friend just brought her new ‘07 over, and her mileage was 48 for 66 miles. She lives nearby and drives the same way I do. Is there some individual variability in these cars? The only factors I can think of are that the previous owner ‘upgraded’ to the Kumho Solus tire, which is only rated as mediocre in rolling resistance in the 11/06 Consumer Report. I do have them pumped up to 44. Also, some of the panels underneath have been removed--the engine skid (I must admit it makes the oil a lot easier to change, and it was gone when I got it) and one in the back, when I had a 1.25 hitch installed. From what I’ve read in posts here, those things shouldn’t be adding up to a 10mpg difference. The highest mileage I’ve ever obtained was 46 on a 90 mile drive with mixed highway and blue highway driving.
By the way, my MFD is broken, but occasionally the overall mileage is displayed, and per my record it seems to still be tracking accurately. The refurb MFD is on the way, costs $460, with $170 to install, just FYI to the ‘04’ers out there that may still be susceptible.
Any thoughts on my less than stellar mileage??

[Paul R. Haller]

We have 2 Priuses an 05 and an 06. My 05 gets on average 6 mpg better mileage then my 06. The difference? Well, my 05 commutes 30 miles one way mostly level and on the freeway. I commute 30 miles both ways through combined city and freeway and I go over a 1600 foot climb each way. The 06 has only 7800 miles on it while the 05 has over 20,000 miles. No matter what I do, I can't come close to her 45 in winter and 55 summer averages. My averages right now are 39 winter 47 summer.
Paul R. Haller

[dcoyne78]

Does your wife have a short commute as well? The Prius does not do as well with short trips, other ideas are is your oil overfilled (best at midway between add and full), what weight oil are you using? Also check the alignment and try pulse and glide between 33 and 40 mph, this is the key to great mileage. Also in warmer weather your mileage will improve. Blocking the grill so the ice stays warmer in winter also helps.

[brick]

I can offer one potential explanation on the Prius vs. HCH thing.

The bread and butter of fuel economy in a Prius is speeds below the 42mph threshold where the ICE is forced to remain on all the time due to the limitations of the power split device. Under perfectly ideal conditions (flat roads, warm weather, and absolutely no traffic) a truly skilled driver can pulse and glide to triple-digit fuel economy. Of course you could never expect that in the real world, as it's a theoretical maximum. Above that speed the Prius starts falling down because the ICE can't truly shut off and there are some (though I think very, very small) energy losses while HSD converts some energy from mechanical to electrical and then back to mechanical while maintaining the super-tall gear ratios on the highway. You can get fantastic mileage, yes. Just not as fantastic as at low speeds.

The HCH is a different beast entirely. Does she happen to drive a 5-speed version? Those are fuel economy monsters when allowed to cruise at anything from 40-60mph. The reason is that the manual transmission Civic employs a lean burn at low engine load, dramatically improving engine efficiency. It also drives the wheels directly through a tall gearbox which I believe to be of some benefit vs. HSD. The CVT version doesn't have the benefit of lean burn, which levels the playing field quite a bit. But it still has the benefit of driving the wheels directly at a very high gear ratio. On the other hand, the Civic can't keep up with a Prius at those low speeds where HSD allows for all kinds of gliding and stealthing.

So it really comes down to two different cars that really shine under a different set of conditions. It could be that her driving cycle favors the Civic's strengths more than yours favors the Prius's strengths.

[walt]

<div class='quotetop'>QUOTE(notperfectlyclean @ Jan 13 2007, 02:48 PM) [snapback]375210[/snapback]</div>

Any thoughts on my less than stellar mileage??
[/b]

swap cars for a month and see how the numbers look.

different cars, different routes, different drivers, different traffic patterns.

lots of variables.

[j4wendling]

[quote]
I can offer one potential explanation on the Prius vs. HCH thing.

The bread and butter of fuel economy in a Prius is speeds below the 42mph threshold where the ICE is forced to remain on all the time due to the limitations of the power split device. Under perfectly ideal conditions (flat roads, warm weather, and absolutely no traffic) a truly skilled driver can pulse and glide to triple-digit fuel economy. Of course you could never expect that in the real world, as it's a theoretical maximum. Above that speed the Prius starts falling down because the ICE can't truly shut off and there are some (though I think very, very small) energy losses while HSD converts some energy from mechanical to electrical and then back to mechanical while maintaining the super-tall gear ratios on the highway. You can get fantastic mileage, yes. Just not as fantastic as at low speeds.

The HCH is a different beast entirely. Does she happen to drive a 5-speed version? Those are fuel economy monsters when allowed to cruise at anything from 40-60mph. The reason is that the manual transmission Civic employs a lean burn at low engine load, dramatically improving engine efficiency. It also drives the wheels directly through a tall gearbox which I believe to be of some benefit vs. HSD. The CVT version doesn't have the benefit of lean burn, which levels the playing field quite a bit. But it still has the benefit of driving the wheels directly at a very high gear ratio. On the other hand, the Civic can't keep up with a Prius at those low speeds where HSD allows for all kinds of gliding and stealthing."



Thanks to Brick for the informative comparison. The civic has the CVT to answer your one question. While I have tried driving tricks, I must admit I am a late convert to radiator blocking. After reviewing MD Fusco's info and the recent thread with pix, I am going to block off in phases to see what difference there may be. I am also concerned that the ICE may be in fact ice cold for longer because the plastic panel under the engine is gone. Other than that, I'm open for any more suggestions.
From other threads, it looks like the cars may have a +/- 10% variation in fuel economy. I wish I could borrow my friend's '07 and see if I got 48 routinely as well. But I need to settle and just get the best I can from mine.
For any technical types that might give this a glance, two questions:
1. Is there in fact any reason to think that the panel under the engine is there to keep it warm as opposed to just clean? Should I consider buying a replacement?
2. Is it agreed that differing rolling resistances in tires would only account for 2-4mpg? Seems I read some conjecture on this matter but don't recall any facts.

[arniesalsared]

<div class='quotetop'>QUOTE(Paul R. Haller @ Jan 13 2007, 03:04 PM) [snapback]375215[/snapback]</div>

We have 2 Priuses an 05 and an 06. My 05 gets on average 6 mpg better mileage then my 06. The difference? Well, my 05 commutes 30 miles one way mostly level and on the freeway. I commute 30 miles both ways through combined city and freeway and I go over a 1600 foot climb each way. The 06 has only 7800 miles on it while the 05 has over 20,000 miles. No matter what I do, I can't come close to her 45 in winter and 55 summer averages. My averages right now are 39 winter 47 summer.
Paul R. Haller
[/b]

We also have 2 Priuses, with the same problem. I have an 04 with 40k and she has an o6 with 10k. I average 4 to 5 mpg more than her and attributed it to her driving habits or tire pressure at first. Last month we tried an experiment on a 60 mile roundtrip caravan into downtown Phoenix. This was with the same tire pressure, gas reset, route, ambient temperature, payload, etc. Results were 49.8 vs 44.7 on the MFD verified closely with a tank refill when 8 gallons were required. The dealer's tech checked the car and said not significant! They are supposed to setup a meeting with the district Toyota rep, but we'll see. I don't see how you can set up a better experiment than the one we did, actually gassing up and tailing each other for sixty miles.

Arnie

[IsrAmeriPrius]

<div class='quotetop'>QUOTE(arniesalsared @ Feb 4 2007, 11:46 AM) [snapback]385197[/snapback]</div>

I don't see how you can set up a better experiment than the one we did, actually gassing up and tailing each other for sixty miles. [/b]

Switch cars for a few days and see if the fuel consumption changes for better or for worse, in one or both cars. Just because she followed you does not mean that her driving technique was as conducive to fuel efficiency as yours. She could have still been pressing the accelerator in situations where you were already coasting and then making up for it by using the brakes more than you did. Based on my almost 30,000 miles experience, high mileage benefits from anticipation.

[j4wendling]

An update on rather disappointing mileage. I was at a low of 34 and blocked the grill, then shot up to about 40. This lasted a week until the weather got much colder (again) and lately I've been thrilled just to get back up to 34, with about 160 on the tank so far. My short commutes kill me as ICE does not like to hold heat at all! My oil is overfilled a quarter inch and I need to get that out, to see what difference that makes.
I thought I could at least compete for the worst mileage, but I see that I can't even come close to that. But it is maddening that there could be as much as a 5-7 mgh difference between randomly drawn Priuses (or Prii--which is correct?)
I thought there was a plastic panel under the ICE, but after seeing other cars I realized that the bottom of the ICE is just hanging in the breeze. When it's 11 degrees, that breeze has a cooling effect. I wonder if a panel would insulate effectively?
The junk-title '03 Civic Hybrid gets 37 mgh all the time, regardless of temperature. It's also hard to mess it up with aggressive driving, though it can be dinted some. Honda made a good engine, or so it appears. I think it does have the super lean burn, which Brick mentioned, despite also having the CVT.

[tochatihu]

Besides all the tire and driver and road and weather and trip length considerations, Prius mpg can be reduced by poor suspension alignment (toe-in) and maladjusted friction brakes. The latter two can be easily addressed, and may serve to make Prius unequal.