World's Worst Mileage?

<div class='quotetop'>QUOTE(Lost In The Hills @ Aug 10 2006, 01:23 AM) [snapback]300701[/snapback]</div>

The first thing I thought of was lots of short trips, lots of hills and low tire pressure. The recommended tire pressure is a bit low I think. To maintain high 40s I keep my tires at 42/40.

But still, unless you're doing a lot of jackrabbit starts, hard accelerations and driving 75 mph on the freeway I don't see why your mileage should be that low.

I'd take it in and complain. They need to do a diagnostic.

And try 42/40 on the tires.

You also might try a long freeway drive at speed limit. (between 55-65.) Drive for at least a few hours on the freeway. If you're not getting in the 40s then, something is very wrong.

 

<div class='quotetop'>QUOTE(Lost In The Hills @ Aug 9 2006, 11:23 PM) [snapback]300701[/snapback]</div>

My worst real tank was my 1st one yielding ~38 mpg (MFD said 45.1). I recently did have a calculated 30.9 mpg, but it was a very short fill: 2.062 gallons (topping off after going 63.8 miles, MFD indicated 47.4 mpg). After that short fill, it took 181 miles for the "guess gauge" to go down 1 pip and another ~37 to go down another pip.

My lifetime average so far is ~45 mpg which isn't on the high side for priuschat. When my tires are overinflated, it's not by much, no more than 3-4 psi over the amount on the door sticker.

No, I've never gotten anywhere near as bad as you describe on a tank. The hills, short trips, city and surbuban driving are hurting things though.

Besides some of the obvious things that you've checked already, perhaps check if the brakes are dragging? Also, are you driving in 'B'? If so, don't. Do you watch the arrows on the MFD? It does help so that you can help learn how to keep the gas engine AKA ICE off unless needed while driving at low speeds (<42 mph). Are you actually turning the power off (pushing Power button) when you leave the car? I heard some a report (possibly apocryphal story) of some dealer figuring out that one Prius owner's low mileage was due to them never shutting the car off.

Don't use the auto climate control at all unless you need the AC and don't use defrost unless you need it [I think the compressor might be used in defrost mode].

If you trust some of those neighbors, perhaps have them try driving your car for awhile to see what kinda instantenous MPG figures they get? Your first 5 minutes will likely be bad, so you might have to go longer. Provided you a have non-malfunctioning Prius but have lousy routes and short trips, I'd wager you should be able to get in the mid 30s w/proper driving techniques.

FWIW, my commute to work is like this 0-8 mins: suburban then expressway, ~20 mins of highway (65 - ~80 mph), and a few mins of city. The return trip is the reverse. The same commute in my 350Z yields ~21-23 mpg.

 

You are switching the car off when leaving it, aren't you?

There was a thread on here about an old couple who complained about getting 12mpg.. Turns out then were just leaving the car, it was locking automatically, but it was actually still on. So the battery was running down and the engine was running to charge it up again 24/7

 

What type of mileage do you get if you calculate it yourself rather than using the MFD number?

 

Are you sure you're putting it in hybrid mode when you turn it on?

I mean, are you holding your foot on the brake pedal while you press the Power button? If not, you are not putting it in Ready mode. Instead I think they call it "IG On" or something, and the ICE runs all the time. The hybrid system is not used unless you are in Ready mode.

If none of this rings a bell, check your manual about starting procedure.

Otherwise, try trading cars with one of your Prius neighbors for a day. See if somebody else can get it up to a more respectable level..

 

<div class='quotetop'>QUOTE(joelparks @ Aug 10 2006, 08:11 AM) [snapback]300741[/snapback]</div>

Sorry, but thats just bad info there...

If you don't have your foot on the brake when you push power, it acts like turning a key in a car (but not starting the car does). first it turns on some accessories, like the radio. then it turns on others, like the windows and AC. however, without your foot on the brake, you can't start the car. there's nothing in the car that will ever cause a "hybrid/non-hybrid" mode - it's always hybrid. Instead, there could be something physically wrong with the car (like dragging brakes, or a problem with the ECU that keeps the engine on all the time), something wrong with the operation of the car (like putting it in B mode all the time or not turning it off when leaving), or something wrong with the driving (like jackrabbit starts, hard stops, and excessive speeding).

The description provided would seem to rule out the driving problems. There was a user who recently posted about B mode - the sales rep told them it was "battery mode", aka an EV mode, instead of engine braking. If the OP got the same missinformation, that could easily be the problem. and as it's been said here, there was a couple who left the car on 24/7. easy mistake to make, as with the SKS you don't have to use the key for anything, and the car is silent when you get out of it. As for the physical problems, thats something we can't really address over the internet - instead, the dealer should be able to examine it. One thing the OP could do is check the energy screen while driving and look closely at the ICE/electric motor usage, see if the ICE is running all the time or something.

 

A couple thoughts: First, have you verified these awful results using good old arithmetic at the pump? You know, miles on the tank over gallons just put in? I'm wondering if you've got some sort of system glitch resulting in skewed calculations. Keeping in mind that I'm only 10 days into my Prius ownership experience, and hardly an expert, I do recall that there's a sub-screen somewhere (at least in nav cars) for doing a re-calibration when you change tires. I don't know if this is for nav functions only (such as when the system has to DR), or whether such tire data, if bad, could impact your mileage data.

Is it possible you've got a dragging brake? That could radically impact your mileage, though I'd think you'd have some pretty obvious secondary symptoms were this the case (burning brake odor, if not obvious smoke in a bad case). Longish shot, but perhaps worth considering.

How about a bad sensor somewhere? Like any other car built today, the Prius is really just a mobile four-wheeled computer that happens to have room inside for five people and some cargo. The GIGO rule (garbage in, garbage out) rule applies to the Prius just as it does any other computer. So, if a degraded sensor is feeding the computer bad data, that could explain the readout.

Of course, the computer itself (either its software or hardware) may be degraded. In that case you could say that the rule is NGIBGO (non-garbage in, but garbage out ). A manual miles-per-fuel gal calculation consistently deviating from your readouts would be consistent with either this or a sensor issue.

Sorry to scattershot you like this; these are just some ideas that popped into my head. Hope you get this terrifying mystery solved soon! Good luck.

 

Check all of the above plus alignment.

The best suggestion is to spend an hour or two on the interstate with the CC on at 55-60 mph. You should be in the high 40s to somewhere in the 50s ... even with the a/c on.

 

I guess my first question would be is the the MPG on the MFD screen as calculated by the car, or is this your calculcation for MPG based on miles driven/gallons pumped?

If you are basing this solely on the cars computer then maybe check a manual calulation and see where you stand.

If you are basing this on a manual calculation is that agreeing with the cars computer (MFD)?

Phil

 

<div class='quotetop'>QUOTE(McShemp @ Aug 10 2006, 10:33 AM) [snapback]300792[/snapback]</div>

McShemp? Is that a new burger?

Never the less, the suggestion from Mr. McShemp is a very good way IMO, to narrow down the problem. Like my prius brother said, on a flat hwy at 55 MPH you should get around 50 MPG. Check it out and let us know.

 

<div class='quotetop'>QUOTE(Lost In The Hills @ Aug 10 2006, 02:23 AM) [snapback]300701[/snapback]</div>

First, you've already filled the car so I assume you did a rough calculation of milege based on gallons pumped and you are convinced that you are getting roughtly the mileage that the MFD is showing.

Second, if your mechanical brakes are dragging, your wheels will get hot. Disc brakes get a little warm in normal use. Drive 5 miles, get out, put your hand on the center of each wheel. If you have a badly stuck mechanical brake (again, almost unheard of on a new car), you'll know it from the temperature - one hub will be much hotter than its mate on the opposite side of the car. Generally speaking, that's a problem with beaters that haven't been properly maintained, not a new car defect. In addition, I have heard of people getting a kink or rust in the parking brake cable, so that the car thinks the brake is released (no red light on the dash) but in fact its still dragging. But that would heat up your wheel pretty well. And again, that's an old-car problem, usually.

An easy test of a stuck parking brake is to turn the car on, put in forward or reverse on some flat surface, and take your foot off the brake. If it doesn't move until you feed it gas, you definitely have a problem, and probably have a stuck parking brake. That's something a mechanic might not notice if they were intent on moving a car quickly from place to place.

If the car rolls easily in drive with no gas, that reduces the likelihood that high mechanical drag is the source of your problem. You might still have a (slightly) stuck brake, but it's not going to cut your mileage in half.

And,when you get right down to it, with that reduction if mileage, if you had a stuck brake, you'd have smelled it by now. It would take a whole lot of friction to cut your mileage like that.

Third, you'd be hard-pressed to get this mileage even if the ICE ran all the time, but the car was otherwise operating correctly. Even so, after 5 min. warmup, on the flat, AC off, rolling about 30-40 MPH or so, take your foot off the gas. Does the ICE shut off? You can hear (windows down) and feel the ICE while driving, or check the (brownish) arrows on the energy screen on the MFD. In fact, I'd go so far as to say that probably the only way you could get mileage like this is if the ICE were running all or nearly all the time. But even then, you'd get mileage like a normal compact car (the Prius is said to be about 27% efficient in the conversion of gasoline energy to motion, a typical gas car is about 20%, if the Prius normally gets say 48 MPG, then running as a straight gas car it ought to get low 30s).

What I'm saying here is that, to get this kind of mileage, a) I bet your ICE runs almost constantly, and b) that might be a symptom not a cause of your problem. Even if it ran all the time, your mileage wouldn't be that bad, all other things being equal. Plus, you imply that your mileage dropped when you started using your AC, which should not have been a significant factor if the ICE were running all the time anyway.

Fourth, also hugely unlikely on a new car but I've seen it elsewhere, a single loose or broken spark plug wire will drop your mileage about like that. But the four-cylinder engine miss would be obvious (tadadum .. tadadum ... ) and any mechanic would spot that in an instant.

Fifth, the gas has to be going somewhere. If the engine were malfunctioning and you were blowing a lot of unburnt hydrocarbons out the exhaust, I'd think you'd see a bunch of check engine lights on the dash, and with that much wasted gas, you'd likely be able to smell it despite the catalytic converter, and would likely overheat the catalytic converter. So, with no check engine lights and no odor, I have to infer that the car thinks the ICE is running OK and that the mechanics notice no obvious problem.

So, it sounds like your engine is running efficiently but your car is not. That's definitely odd.

Sixth, invite your Prius-owning neighbor to drive the car, see if anything comes to light.

Finally, if its some other mechanical problem causing excess drag, then some part of your car is getting really really hot as you drive. Has to be, wasting that much energy. You'd think you'd get a warning light from that if it were anywhere in the drive train, so ... that seems like a non-starter as well.

So, my summary:

Is your computed mileage about right based on filling the tank?

Will the car creep forward and backward, on level ground, with no gas? Are the front wheel hubs about equally warm after driving, and the rear wheel hubs about equally warm after driving?

Does the ICE shut off when coasting at moderate speed on level ground, after warmup?

If yes to all of the above, then I think you're right, this is something pretty exotic. But definitely wrong. I drive almost nothing but short trips and manage roughly 47 MPG year round. Good luck.

 

<div class='quotetop'>QUOTE(cwerdna @ Aug 10 2006, 04:11 AM) [snapback]300715[/snapback]</div>

That's a great recommendation!

I'd encourage you to also drive a street where you can do between 35-40 mph for about 20-30 minutes, relatively flat and see if you can get in the 50's or higher. If you can't then definitely there's something wrong with the car. Assuming you turn it off, ^_^ (I know sounds silly but it is so easy to leave on!). When I lived in Pasadena, Foothill Blvd to Azusa was such a 20-30 minute stretch of road. Huntington Beach is another good test route, you know what I mean. BTW, what is your typical mileage on those flat streets you referred too?

My regular route yeilds lousy mileage, however, doing the above I routinely get 60 mpg or higher.

<div class='quotetop'>QUOTE(joelparks @ Aug 10 2006, 08:11 AM) [snapback]300741[/snapback]</div>

Wow! I've never heard of this, Is that a 2006 thing? If I don't put my foot on the brake and press power, I don't leave the garage!

<div class='quotetop'>QUOTE(grasshopper @ Aug 10 2006, 10:03 AM) [snapback]300810[/snapback]</div>

Again all good stuff! I'd concur even in heavy traffic!

 

<div class='quotetop'>QUOTE(berylrb @ Aug 10 2006, 11:40 AM) [snapback]300870[/snapback]</div>

Wow! I've never heard of this, Is that a 2006 thing? If I don't put my foot on the brake and press power, I don't leave the garage!
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No, it's not. once again, this is simply bad or missunderstood information. hitting power without the brake pressed simply turns on the accessories, but not the ICE. there is no such thing as "hybrid/non-hybrid" mode

 

<div class='quotetop'>QUOTE(eagle33199 @ Aug 10 2006, 12:43 PM) [snapback]300878[/snapback]</div>

I was really confused when I read that. I thougt I was doing something wrong all this time. I felt like I was left out of the club, and nobody showed me the "secret handshake"

 

One last question for the OP: Are you leaving/driving immediately after you've powered on or are you waiting for the car to "warm up"? If you are doing the latter, don't.

 

One more thing - have you hit the reset button recently on the MFD? it's possible that there was one occasion where you didn't turn it off or something and ran out a ton of gas, and it just hasn't recovered from it.

Of course, this is a moot point if all you're seeing is 25MPG 5 minute bars.

ok, i lied, two more things. the second is the type of gas you're using. are you sure you didn't somehow fill up at an E85 station (even though the prius is supposed to be E85 yet, i would guess you could get through a tank or two without any problems)? E85 does cause a dramatic drop in mileage from engines, even if they're designed for it.

 

<div class='quotetop'>QUOTE(eagle33199 @ Aug 10 2006, 01:38 PM) [snapback]301064[/snapback]</div>

Yeah, I was thinking that too. (eagle, I suspect you meant to say, even though the prius is not supposed to be E85 yet)

 

<div class='quotetop'>QUOTE(wilco @ Aug 10 2006, 03:52 PM) [snapback]301072[/snapback]</div>

yeah, you caught my typo... getting to the end of the work day here, i just wanna go home :-p