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After over 78,000 miles of driving Prius, I have yet to encounter that situation. In fact, I haven't even come close to it.
In other words, is it quite a bit more rare and far more predictable than has been implied.
JOHN
Break-In Oil becomes increasingly thicker and thicker. By 4,000 miles, you are pushing it... not damaging anything, but hurting MPG.
If you live in an area with a lot of sand & dust, you may actually have an impaired engine air-filter. That will reduce MPG too.
You may have picked up a counter-productive habit, misinterpretting what the Multi-Display is telling you. Some owners unknowingly fight the system when they see the green MPG bar drop really low during acceleration and climbing hills.
JOHN
Interesting you should mention this for Prius. The Honda 2.4L comes with break in oil that the factory recommends keeping in as long as possible (up to the scheduled 10K maintenance). I kept mine in for 7K, which is 2K past the normal 5K "severe" interval for the 2.4L...
Thanks,
Mike
Your best MPG is not found while the battery is recharging.
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In the winter time, instead of running the car at idle waiting for the engine to warm up, put the car in gear and drive very gently for a few minutes (provided of course that your windows aren't caked in ice...use common sense). The car will actually warm up faster and, from what I read, the negative effects of uncombusted fuel will be lessened. Improved fuel economy, better performance, less pollution.......what's not to like?
More on the extreme side, may I add to try and not use cabin heat until the engine is completely warmed up. With burning so little fuel, you can have potentially better results as you are not heating both a cold engine and cabin at the same time.
--I usually don't turn on the heat with a cold engine if I'm stuck at a stoplight. The engine would just keep running to heat the cabin. I turn it on as soon as the light turns green and my engine has to be on anyway to accelerate the car.
Avoid braking (wastes energy).
Watch your Instant MPG Bar & keep it at 80 or higher.
troy
Avoid braking (wastes energy).
Watch your Instant MPG Bar & keep it at 80 or higher.
troy
Avoid driving personal vehicle, take public transportation, you save money, evironment and natural resources.
:-)
Sorry, couldn't stop my self.
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.
"Avoiding braking isn't advisable, but avoiding abrupt braking is."
.
I've found that if I look ahead & plan, I only need to brake 2 or 3 times during my daily 70-mile commute.
So to repeat: Avoid braking...it wastes energy.
troy
--Back on topic, avoiding braking is advisable, as long as safety is not jeopardized...but we all knew that already...right?
--Just curious: Does a smaller HP engine warm up faster than a larger, more massive, HP engine with all other conditions being equal?
--Would the mere act of using the heater reduce the efficiency of the engine in the winter by pulling waste heat away from it (e.g., would there be any difference in fuel consumption driving up a long hill with the heater on --discounting the energy required to operate the fan-- as compared to driving up the same hill with the heater off?)? Or does the amount of heat vented to the cabin have such a negligible effect on engine efficiency as to be a non-issue?
--If the cold weather has a negative effect on battery efficiency, then would it make sense to keep the cabin as warm as possible in the winter so as to warm up the battery pack in the rear of the car?
--Is the forced vent heat supplied solely from engine combustion? Or is there a supplementary electric heating element?
I understand the Prius has an electric heater, not tied to engine coolant so I suppose it wouldn't matter in that case.
HCH has a conventional heater core.
ICE is more efficient when warmed up. Your engine thermostat keeps the coolant from flowing into the radiator to keep the growing heat from dissipating into the air, holding the heat inside the engine block until it reaches operating temperature.
The heat has a 2nd designed path to escape the block while it is warming up, the heater core, which acts as a mini radiator.
The only thermostat for this mini radiator is the cabin temperature control.
I know in the past vehicles I've been trapped in a slow moving traffic jam during the summer, only to find the temp gauge climbing higher & higher.
I've been able to vent the cabin, set the cabin temp to hot, blower fan on high to stabilize my rising engine temp. Alot of heat can be dissipated from the engine out of the heater core.
It makes sense to me that the engine will take longer in freezing temps to heat if I turn on that "2nd radiator" before the engine has a chance to fully warm up.
It's true that batteries are less efficient when cold, but in the case of HCH, how long does it take for cabin heat to actually reach the batteries? First the engine would have to heat both itself & the cabin, then the back seat cushion, then the electronic plastic & metal casings, then the batteries themselves.
There is a vent on the top rear deck for the electronics. I wonder does this direct cabin heat to the batteries, a vent for the electronics or both?
The batteries also heat by themselves as they are being used.
I think the 1st priority would be getting that ICE warmed up.
Does it make any sense?
Also high tire pressures which give you better mpg, also decrease the contact patch between tire and road/snow/ice.
So what do you guys suggest or do for winter driving? What's more important safety - as in better control and braking, or mpg? Since many of you are talking about how to save the tiniest bit of gas by not warming up the vehicle and running the heater til warm, I'd guess you're not advocating snow tires?
Also avoiding braking as long as possible based on your determination of what is safe, is not a good idea. As you may 1 second be on pavement and the next on black ice, and never have known the difference, you may be in for a bad surprise when you estimate where you're going to stop. You may find yourself hitting a pedestrian in a crosswalk, a car stopped at a light or Stop sign, or simply slide right thru the intersection. For safety's sake you start braking early, testing the road conditions, and giving yourself a good margin of error.
Sorry if you don't like this post, but as on many of these forums I point out that all decisions have positives AND negatives. Don't just focus on the positives. To make decisions based on MPG-alone, is not in your best interest or anyone else's.
No, No, No
Higher pressure is better for handling on dry pavement, handling on wet pavement, and on snow as well. That's why many people put on narrower tires in the winter.
If you have a link that says less contact patch is better for a street/passenger car, then please provide it. Here is my professional link - I think Michelin knows a little bit more than we do - stating that their Michelin Arctic Alpin has a "high contact tread-design and expanded contact patch". This is Note C under the tire picture.
http://www.michelinman.com/assets/pdfs/doc_arcticalpin.pdf
By saying don't use high pressure, I'm not advocating low pressure; you should use recommended pressure in this tire.
By the way do you think it's worth people who may experience snow to use snow-tires to increase safety?
The first 2-3 miles are worse, and the temp gauge shows normal at about 3 miles.
I notice improvements after I've driven 3, 7, 10 & 20 miles out.
If hybrids continue like the Prius offering all the creature comforts such as AC, stereos and power options, I would include "an effective heater" as equally important. And the only way to produce heat is to burn fuel. Of course you want to start drivng right away too, so the best thing would be to begin driving after 30 sec. of getting the oil pumped around the engine. But you need to burn some gas and get that car up to temperature.
Here are published numbers for Goodyear Tires with a Max Sidewall Inflation Pressure of 35 PSI for vehicles that 'recommend' a pressure below the maximum.
#############################
Dry Macadam Surface
(Stopping Distance in Feet)
2001 Dodge Grand Caravan Sport__20 psi__28 psi__35 psi
Full Depth Tread with ABS_________75.5____76.2____75.8
1/2 Depth Tread with ABS__________69.9____68.1____66.3
Full Depth Tread without ABS______98.3____95.9____91.6
1997 Ford Ranger
Full Depth Tread with ABS_________80.8____78.2____77.6
1/2 Depth Tread with ABS__________79.0____74.8____71.4
Full Depth Tread without ABS______97.8____96.5____94.1
#############################
0.02 Inch Wet Macadam Surface
(Stopping Distance in Feet)
2001 Dodge Grand Caravan Sport__20 psi__28 psi__35 psi
Full Depth Tread with ABS_________79.8____78.5____77.1
1/2 Depth Tread with ABS__________84.7____73.7____81.4
Full Depth Tread without ABS_____111.1___110.2___108.6
1997 Ford Ranger
Full Depth Tread with ABS_________83.8____81.5____79.8
1/2 Depth Tread with ABS__________91.5____89.4____84.6
Full Depth Tread without ABS_____131.9___126.0___118.4
#############################
0.05 Inch Wet Macadam Surface
(Stopping Distance in Feet)
2001 Dodge Grand Caravan Sport__20 psi__28 psi__35 psi
Full Depth Tread with ABS_________80.0____81.1____82.7
1/2 Depth Tread with ABS_________103.7____99.7____92.2
Full Depth Tread without ABS_____118.0___112.2___111.7
1997 Ford Ranger
Full Depth Tread with ABS_________89.7____86.0____81.5
1/2 Depth Tread with ABS_________125.7___118.5___104.5
Full Depth Tread without ABS_____142.9___134.8___125.7
#############################
Specialty snow tires on specific snow conditions are, obviously, a special case, but it has nothing to do with the general behaviour of the average passenger tire in most conditions. It also doesn't cover slush where again, the ability to bring maximum point pressure to bear is more important than a big footprint.
Manufacturers set the vehicle 'recommended' pressure for many reasons besides safety and performance. Remember the Bridgestone fiasco with Ford. Ford recommended a low pressure on the Exploder, because it decreased the chance of rollover (at least partially because you couldn't corner as fast with the sidewalls rolling over ). But, that caused the tires to blow out. Bridgestone took the heat, but it was Ford's fault. The tires were rated for higher inflation, and should have been run there.
Most instances now where the vehicle manufacturers recommend lower tire pressures are for comfort.
But, in the vast majority of real world situations you will get better performance and longer tire life by going closer to the sidewall rating. The possible exceptions being mud and some rare snow situations where you are looking more for a snowshoe than a tire. But, Slush, Ice, and Plowed snow all benefit greatly from higher pressure.
What's really bad is when people buy into this 'big footprint' myth and let air out of their tires in the winter
I'm not saying to always inflate tires to the sidewall max, but 99.9% of the time you'll do far better to inflate a bit over what's printed on the vehicle. I know many tire professionals who use the '5 Pounds Over' rule on their own cars. IE, if the vehicle manufacturer wants 28 pounds in the tires, they do 33. If the manufacturer wants 32, they do 37.
This has another benefit. It makes sure you don't run under-inflated, because it's ALWAYS far safer to be a few pounds over than a few pounds under.
--Talk about gross assumptions! You're missing the whole point of this forum, kernick. It's not, "Hybrid tips: Optimizing Safety." It's all about Fuel Economy, baby. Your comment is like telling a NASCAR driver that he doesn't care about safety because he and his mechanic happen to be having a discussion on how to make the car go faster. I would hope that people would have half a brain to use common sense when choosing whether or not to implement some of the suggestions presented in the forum. If you're dying of hypothermia, for example, by all means don't let my fuel saving tip stop you from turning on your heater. I don't want to be accused of cold-blooded murder...haha.
--About the braking: unless I miss my guess, no one was advocating screaming up to a stoplight and braking only at the last possible second. I believe the other gentleman was simply saying that from a fuel economy standpoint, it's better to coast gradually up to a stop letting the car slow itself and gently braking when necessary to come to a rest, rather than flying in and relying heavily on the brakes to do the job. In fact, safety-wise, if you're talking about ice, this would be a much better way to come to a stop since the momentum change would be gradual. Who's to say that when you're "testing" the brakes you're not already on black ice? Then you may very well spin out and swipe the guy next to you. Again, judicial use of the grey matter is probably the best tip I can give.
___Excellent post. I hope you don’t mind if I spread that all over the net ;-)
___Here is one for the rest of us
http://www.hydrogen-boost.com/february2002.html
___Personally, 50 #’s (6 over Max Sidewall is my own norm) and you can take the 75,000 miles at those pressures anyway you want. Since I am not racing up to stoplights, am not driving at much over the speed limits if at all, my braking distances will be far shorter no matter what pressures I was running at.
___As a tip, my best stops happen when I don’t use the brakes at all. It requires really good timing of course but here is an example You are cruising down the highway at 60 mph. You have an upward sloped off-ramp. Average height at the top of the ramp is ~ 30’ or so. Let off the gas ~ ¼ mile before and not only have you bled off the 10 - 15 mph by the time you hit the ramp (60 mph down to 45 mph or so), sometimes you can bleed off the rest of that 45 mph to 0 mph with quite a bit of your Kinetic swapped for Potential just as you hit the stop sign at the top of said off-ramp. No brakes, maximum FE, and in case the ramp were slick from ice and snow, very very safe. It works with lights, signs, off ramps, and traffic obstructions up ahead.
___This is just one of the tips I like to pass on to help others achieve higher FE by simply stating the obvious. Drive like you don’t have brakes and your FE will improve to hypermiler status almost immediately.
___Good Luck
___Wayne R. Gerdes
Maybe the name is wishful thinking on Michelin's part. I personally use Michelin's on my Suburban. In the Arctic the only tires that seem to hold up in the extreme cold and harsh roads are Toyo & Bridgestone. When they send up a new vehicle with heavy duty tires meant for the rest of the world they get replaced the first year. The gravel and cold rip them to shreds. If you get 5k miles up there on OEM tires it is considered good. I have never seen a Michelin used in the Arctic. Tall hard compound 10 ply tires are what are generally used. That is all the tire guys carry.
It provides cabin heat more quickly than our other vehicle which consumes 3x the fuel.
I think allowing the engine to concentrate on heating itself up completely before sharing it to the cabin works for all vehicles , not just HCH.
(Except Prius which uses electric)
If an engine can reach its operating temperature faster, that warmed up engine gives better MPG.
At least you should always have enough battery power to get the engine started. ;-)
What you give me first is tell me I'm wrong concerning snow-tires. When I prove otherwise, you then post data - which is good data, but has nothing to do with snow tires, and add "Specialty snow tires on specific snow conditions are, obviously, a special case, but it has nothing to do with the general behaviour of the average passenger tire in most conditions."
Well gee, since I was talking about a specialty case, and then you comment on it, I'll just assume that you missed my mention of "snow" in front of the word tire. And you were correct all the time, just about something else. ;-)
And you're right that I never mentioned about lowering the tire pressure either on a regular or snow tire. I suggest just as the NHTSA to use the manufacturer's recommended pressure, or a few psi higher (I believe they recommend a max. of +4psi).
Where I live, good modern all season tires like Michelin Hydroedge or Goodyear TripleTreds are adequate for any snow situations where sane people would be driving. In areas that don't get regular, long-lasting snow, the danger isn't your sliding, but the 'other guy' who doesn't know how to drive on snow or ice. Given the driving skills of people locally, I just stay off the road when it's to the point that actual snow tires would be required.
I've lived in snow country too, and there's clearly a time and place for snow tires. In fact, I'd like to see more places re-legalize studded tires because modern studs don't chew up pavement nearly as much as the old versions.
Yes, you lose mileage with snow tires on dry pavement, but you lose mileage with any tire in snow anyway.
If you're driving on snow or ice 80% of the time, it may make sense to run snow tires.
If you're driving on dry pavement 95% of the winter, and on minimal snow and slush the rest of the time, good all-seasons are fine.
But, either way, I'd still keep them well inflated.
There's a reason the old VW Beetles were monsters in snow. It's because they had skinny tires that were hard as rocks
Once again, I've heard from many sources that the Prius does not use engine heat, but rather an electric heating element(s).
Prius heating is independent of engine temperature.
Perhaps you are confusing heat with AC? The 2004+ Prius use an electrically powered Scroll-type compressor for their AC (2001-2003 used a conventional belt-driven compressor).
Culliganman (sometimes complexity breeds frustration)
Sounds like the jury's out on the "improved" climate control in the 2004+ models.
.
NiMH batteries like being cold. Plus, the DC/DC converter throws off plenty of heat into the battery compartment... you don't need to add to that.
As for heating vs. engine efficiency, I think it depends on your engine. My 220 hp Avenger burns through tons of fuel & has tons of heat to spare. I could turn my car into an oven, and there'd be no impact on my 30 MPG average.
In contrast, my 67hp Insight barely has enough power to move the car down the road... it's throwing off almost no waste heat... so if I turn on the cabin fan, my little engine will cool off & end up burning more fuel to compensate.
troy
I have heard that it is oxygenated, which reduces pollution in older cars, but results in poorer gas mileage across the board. And so I've been assuming that my mileage will improve once spring rools around.
But I don't know for sure, so I'd love to hear what you folks know about it.
There was also a brief conversation about oxygenated fuel starting with this post:
marklud, "What about fuel types & gas mileage?" #55, 27 Dec 2003 2:28 pm
kirstie_h
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Thanks for the pointer! I followed your advice and posted the question over there.
Culliganman (cutting the Prius some slack)
P.S. Ever notice the car mags always road test cars in somewhat ideal temps and weather conditions?
Does anyone know if this was true?
___I am sure the article mentioned N2 (78% of what is in your tires right now is N2) as many people are doing this now, not H2. You would be filling up every third day (not cheaply either ;-)) if H2 was in the carcasses.
___Good Luck
___Wayne R. Gerdes