That's it, I'm walking. gas up 33 cents since Monday, - Page 8

Is there a website that tells you the "real" MPG of various cars, or is there a number which you take off of what the dealer says to make it more accurate? For instance say the sticker says it gets 20/25 mpg, would in reality it get say 15/20 or 17/22, etc?

My AC went out at the right time so I'm getting a little better gas mileage I suppose, but I live in AZ so it's a little unbearable at the moment.

If you are driving around with your windows down you are probably getting worse gas mileage than if you used your AC with the windows up (unless you are just driving slowly around town in city traffic).

Hee hee! That brought back memories. I used to drive a cab in Phoenix. A big black Lincoln Towncar. No speedometer (Scottsdale to Sky Harbor in 25 minutes, before the freeway!), broken gas gauge, and no AC. It was pretty brutal.

Then some cabbies from my company started to get shot in the barrio, and I quit. What a weird summer that was.

Anyway - this thread has got me thinking seriously about buying a "road" or "hybrid" bicycle. But I don't know anything about these things. The days of the cheap Walmart Schwinn are over, I guess. Don't mean to hijack this thread, but if anyone has a good info website on city bicycles, I'd like to see it.

MC

As a bicycle commuter for the last 4 years, I'd love to help folks get into biking to work for those that can (and there's a lot more who can and think they can't. It's not as hard as most people think.).

Micah, feel free to email me or start a new thread. I agree, it's probably better to do this in another thread and lately, I've been kind of busy elsewhere to check out AH too much.

A hybrid or touring bike would be the best, it would typically be more comfortable than most road bikes which many are geared towards racing even though 99% of the bike population do not race. A touring or hybrid (or mtn bike) will have a more upright position and be more comfortable to ride and also have larger width/volume tires which will give a more comfy urban ride than the skinny racing tires inflated to 110psi.

Most important thing to do is look for a good fit, make sure it has eyelets to mount a rack on it and fenders if you plan on riding in the rain. Start slow, perhaps ride the route on a weekend, etc. etc.

Anyway, I am always glad to help others to get into cycling so feel free to email me...

Jay

They did that 'myth' on Mythbusters. IIRC, they proved it didn't make much difference...

Cars weren't as aerodynamic when the window-myth started. Roll down your 64 Cadillac "city aquarium" window and it causes enough drag to parachute your new vynil top!

Yeah, take the top off my "essentially the same aerodynamics since WWII" Jeep Wrangler and the wind resistance goes DOWN, not UP. Roll down the window with the top up and it has the aerodynamics of 2 bricks instead of one.

but wasn't the point to show that the loss in aerodynamics (with the windows down) offsets the gas you use when using the A/C (with the windows up)?

The myth stated that riding around with the windows open uses more gas than the AC. The Mythbuster's results were that it didn't really matter, any loss in MPG from less aerodynamics was about equal to the loss from AC. This only took into account a modern vehicle and only one modern vehicle at that. I think the point being made is that when the myth started, the wind resistance caused by huge windows with crappy airflow characteristics was a much greater detriment to MPG than todays more aerodynamic designs, so essentially the myth was true in those days (and for those that drive a Jeep Wrangler today).

Ah, Gotcha!

"and as the crowds drive past a little flat car
you know they saved a lot of gas
but they didn't get far
in a yugo"

Well, if nothing else this thread reminded me of the hilarious "In A Yugo" song. I'll spin it tonight and eat PB & nanner samich.

They did do that on Mythbusters (episode 22) but in their test they found a big difference, and that having your windows down without A/C did lower their gas mileage.

Here is a summary on the test done by Mythbusters:


This surprised me as I thought the A/C in automobiles runs off the electrical system which is powered by the turning of the wheels when the car is moving, not the burning of fuel - thus the reason why running your AC should have no effect on gas mileage.

Regardless, no one is going to get me to turn off my A/C during the summer months in Texas!

I love Mythbusters to death, but many of their conclusions are in no way definitive,a nd in many cases are blatantly wrong (I shook my head i disbelief when saw the first chicken gun episode).

There were many methodology flaws in the test they did. The worst flaw was that the test took place at about 40 mph. In a real trip from point A to point B, the 40 mph drive would take longer than a 60 mph drive (hence require more AC) and would cause much less drag with the windows down.

The second flaw in their test was that it was performed with two different cars. Either they could have used the same car, or else used a much larger sample to average out the variance that one would expect.

As it was, it was interesting but purely antidotal. I certainly would not use the conclusions as "data" in serious discussion.

Scott, I didn't watch the episode, only read the summary report on it, but I'd have to disagree with you on the validity of a 40mph test. Besides the fact that driving with your window down on a freeway is less than desirable, but even in rush hour traffic where most people spend their time in their vehicles, they wont be doing 60mph.

I do agree that while entertaining, Mythbusters is really a great example of how to run a really bad test, and if they used two different model cars, then the results are 100% meaningless... and I'm shocked that even they would do that. Are you sure they were different models? If so, then that may have to go down as one of their worst tests ever!

In fact, they shouldn't even use different cars of the same model. They should use the same car and run all of the tests under the same track conditions in order to isolate the effect of running with the windows down vs widows up VS windows up w/ A/C.

There's just no way to do that, as even environmental changes (such as temp, humidity, etc) can change the result (ie run the test for 3hrs, then do it again but it's 3 hours later and may be hotter/cooler, etc).

Using 2 cars of the same model would introduce it's own variable. You can try and mitigate that a bit by testing the two cars in an identical manner and see what the variance is and apply that to the restuls, not perfect, but it would be a bit better.


There are a few parts to an AC system, but the compressor is hooked up to the engine and is driven by a belt, when you engage the AC the clutch in the compressor "activates" and turns it, which causes drag on the engine. That's a bit simplified, but that's the nuts and bolts of it.

Andrew

They used two different cars of the same model.

In my mind, the purpose of doing such a test would be for the driver to know the trade offs between comfort and gas milage. While I agree that I seldom even hit 40 mph in rush hour, it is also true that the amount of wind generated at 40 mph wouldn't be enough to make me ocmfortable so a test at that speed would be moot. Therefore, I think that the test is only valid at those speeds that actually generate enough wind where driving with the windows down might be considered comfortable (and rush hour traffic usually doesn't cut it).

Of course, as you pointed out, none of this matters where you live (I lived in Houston for 7 years) where driving with the window down is the equivalent of aiming a very powerful hair dryer at yourself.

Assuming this is true; as I said before, I know nothing abourt cars; it would still make a difference to milage but would depend on how you were driving.

If you were cruising on the highway, the the ac running off the wheels would cause some extra resistance to the wheels turning and so the engine must provide enough power to balance the resistance from air, rolling friction, and the AC.

If you're doing a lot of stop-go in traffic, then during the stop phase, some of the energy that would normally be just wasted as heat in the break disks is being used to run the AC. This means that the impact on gas milage is reduced but not eliminated.

This 'wasted' energy is part of what's responsible for lower milage in city driving and it's what hybrid cars try to address by charging up the battery during the breaking phase.

The AC is not run off the electrical system in an automobile, don't know where you heard that. It is run off the belt(s) attached to the crankshaft at the front of the motor, just like the fan, power steering, alternator etc. It is essentially a compressor that is turned by the belt, just like the compressor in residential AC is turned by an electric motor. Any drag on the engine causes a loss in shaft horsepower, so the drag from powering the AC compressor means you have to use more gas to maintain speed.

Also, a car's electrical system is not powered by the wheels, it is powered by the alternator, which is powered by the belt(s) attached to the shaft, which is powered by burning fuel, just like the AC.

> Regardless, no one is going to get me to turn off my A/C during the summer months in Texas

Same here in Florida- I don't really care if A/C lowers the mileage, because with it off, it's like sitting in a steam room. But once the car is cooled off, the air only needs to be on the lowest setting, which probably doesn't use much fuel.

I also have to feed my car (2000 Grand Prix GTP) premium for optimum HP (and the manual says to use < 91 octane only in emergencies). But honestly it only makes a little difference, since these days, what's the real difference between $2.57 and $2.77? Still about $3 difference for 15 gallons.

When a tank cost $26 or so, the difference between $26 and $29 = about 10-11% difference. Now that a tank is more like $39, the difference between $39 and $42 is about 7% The higher prices go, the less difference paying an extra measly $.20 for premium makes. After all, gas dropped $.20 here in 12 hours since 7am when I got $15 @ $2.97 Now I could buy premium for what regular cost yesterday.


My GTP is EPA rated at 18mpg/28mpg for the supercharged 3800 V6 '00 GTP. Personally I think the highway ratings are totally off - personally a small V6 (say 2.5L - 3.4L -ish) is the optimal choice for freeway driving IMO. I get much better mileage on the freeway in my GTP these days than I used to in my 4-cylinder 1989 Corsica. Then again, my GTP runs at 2200-2300RPM or so @ 80mph, whereas my Corsica ran way WAY higher RPMs than that.


During a trip to Toronto a couple of years back and a few other long road trips, I got 30-31mpg on the freeway - and that, at 75-85mph (my normal cruising speed is 80mph in Michigan but slow down to <75mph in Ontario where the speed limit is lower).

My normal mileage is about 25mpg - lots of 60mph highway driving and 80mph freeway driving. In city conditions I do poorly, like when we were in Las Vegas/LA/Detroit, etc. But I don't live anywhere near a real urban area, I would buy a peppy 4-cylinder or small V6 car for city driving, if I did.

the current Toyota Prius does not use an engine driven AC compressor--it's compressor is electrically powered off the high voltage system. This eliminates the need to keep the gas engine running at stops when the AC is on Max, as was the case with the 1st generation Prius.

Many current models are now using electrically driven Power Steering pumps, perhaps pioneered by Toyota on the second generation MR-2. Ford, Mazda, and GM are among the mfgs now using electrically powered ps.

The Prius gets a bad rap for not really getting the 60mpg in town that the EPA sticker claims, but in fact will get mid-40s in city driving, at least twice what the average car it's size will achieve in real-world city conditions.

...

Deleted my post. It had to do with Hurricane Katrina. Don't want to appear insensitive to those who are going to have to put up with it

Maybe so, but I think the EPA needs to revamp their testing badly. There could be a consumer survey something or other for non-first year models. I.e. put 50 mpg highway 60 city and then say, on the prior year model, consumers surveyed reported an average of 40mpg combined.

Post-Katrina: Gas prices spike!

Yesterday: $2.54
Today: $2.65

The worst is yet to come.

- Colton

I was able to fill up for 2.41 yesterday and I did FILL up considering Katrina and that they've closed down most of the oil rigs.

About 3 months ago I put in an Airaid system in my Jeep. It is in essence a high performace air filter. I've calculated the increase in MPG and figured it to be 1.5-2 MPG increase. I figure it will pay for itself in about 6 months.

What's the deal with the 9/10ths of a cent thing?

For example: $2.99 (9/10ths) per gallon:

Since most people buy an average of 10 gallons, it's their way of getting extra $$ out of the deal while you assume you're only paying $2.99/gallon.

So in actuallity, you're paying $29.99 per 10 gallons instead of $29.90 (like you imagine you are) - That's almost an extra dollar for every 100 gallons. It might not sound like much, but it adds up.

It's very similar to the $499.99 sales which make it seem more affordable than if you saw $500.

A temporary solution that I haven't seen mentioned is a temporary federal mandate on the reduction of 'blends' of gasoline.

Refineries have to make an inordinate amount of 'blends' to meet with different states' requirements. These also change during different periods of the year. Often times these 'blends' don't store well, so stockpiling can't occur as much.

While I loathe federal interference, I think as long as it's stated what the timeline would be (2 years - 5 years) and the number is reduced to a management amount, then refineries could then generate more and more could be stockpiled, thereby increasing supply.

In the past couple weeks I have made an effort to alter how and where I drive in an effort to increase my average MPG.

I've increased my average MPG from 20-21 up to 25-26. That's an increase of over 20%. Not bad.

I've been able to do this by changing some of my driving style such as accelerating more slowly and reducing my speed on the interstate.

I've also changed my habit of driving out at lunch through a drive-thru 3 or more times a week. Now I stay in for lunch (I work at a hospital, so luckily I have access to a cafeteria at work). These type of outings were a real drag on my fuel economy.