Interesting trip
#1
06-26-2005, 07:40 PM
Interesting trip
We just got back from a weekend trip, during which I gathered a few interesting bits of data. Our '05 FEH is a couple of months old, with somewhere between 1K and 5K miles on it. Up to now, I have been doing basically rural driving, with a little "city" driving (low speed, flat terrain, lots of short stops - mileage heaven) thrown in, and have been averaging about 30 mpg (lower when it was colder, and when traffic has required more aggressive driving than I would have chosen on my own; higher when conditions are ideal, as they often are on my daily 30-minutecommute).
I thought I'd probably get less than that on the highway, about 300 miles or so at 65-70 mph, with a fair number of hills as we drove through the mountains in PA, and A/C on most of the time. But lo and behold, on the way down (Ithaca NY to Baltimore MD, fresh tank), we arrived in B'more with the gauge reading 31.8 mpg! The next 100 miles or so, on the beltway and other highways around the city (much hillier than I'd remembered from my childhood), we lost mpg, ending the tank at 30.5. Overall, I was pleased with the highway mileage, which beat the EPA estimate of 29 for my AWD model. Also, I found it interesting that if the gauge is to be believed, my FEH got better mileage on the open highway than it does "around town" - though most of my "around town" driving is not true "city" driving.
Coming back, however, I learned another thing - weight really does matter. We were loaded, with about 200 extra pounds of tools, furniture, etc., and traversing the same route in reverse (direction, not gear
), we only got about 29.2 (according to the gauge, again on a fresh tank but it's not empty yet). The only thing different was the extra load, so that seems to make a difference.
This prompted some speculation and discussion in the family about how "they" come up with the EPA mileage estimates. Could someone point me to a source for learning more about the conditions used in determining those numbers? Is the driving done on a track, on flat or hilly terrain, with what kind of a load in the car, etc.? TIA!
C.
I thought I'd probably get less than that on the highway, about 300 miles or so at 65-70 mph, with a fair number of hills as we drove through the mountains in PA, and A/C on most of the time. But lo and behold, on the way down (Ithaca NY to Baltimore MD, fresh tank), we arrived in B'more with the gauge reading 31.8 mpg! The next 100 miles or so, on the beltway and other highways around the city (much hillier than I'd remembered from my childhood), we lost mpg, ending the tank at 30.5. Overall, I was pleased with the highway mileage, which beat the EPA estimate of 29 for my AWD model. Also, I found it interesting that if the gauge is to be believed, my FEH got better mileage on the open highway than it does "around town" - though most of my "around town" driving is not true "city" driving.
Coming back, however, I learned another thing - weight really does matter. We were loaded, with about 200 extra pounds of tools, furniture, etc., and traversing the same route in reverse (direction, not gear
), we only got about 29.2 (according to the gauge, again on a fresh tank but it's not empty yet). The only thing different was the extra load, so that seems to make a difference.This prompted some speculation and discussion in the family about how "they" come up with the EPA mileage estimates. Could someone point me to a source for learning more about the conditions used in determining those numbers? Is the driving done on a track, on flat or hilly terrain, with what kind of a load in the car, etc.? TIA!
C.
#2
06-26-2005, 08:01 PM
Re: Interesting trip
I think they do mileage tests inside labs, with cars propped on machines to allow the wheels to spin. Try http://www.hybridcars.com/mpg-mystery.html to find out more about how the EPA does their estimates.
We are waiting for our '06 FEH to arrive in a few weeks!
pt
We are waiting for our '06 FEH to arrive in a few weeks!
pt
#3
06-26-2005, 08:08 PM
Re: Interesting trip
Hi Sweetbeet:
___The following should help ...
EPA's Fuel Economy and Emissions Programs
___In detail, the following CFR should give you all you need ...
Part 600 – Fuel Economy of Motor Vehicles
___Good Luck
___Wayne R. Gerdes
___Waynegerdes@earthlink.net
___The following should help ...
EPA's Fuel Economy and Emissions Programs
How are Vehicles Tested?
Vehicles are driven over identical driving patterns by professional drivers in controlled laboratory conditions on a dynamometer, which is like a treadmill for cars. The conditions that occur during driving, such as wind drag and inertia are accounted for on the dynamometer. There are two types of tests that are conducted: city and highway tests.
The city test is approximately 11 miles long and simulates a stop and go trip with an average speed of about 20 miles per hour (mph). The trip lasts 31 minutes and has 23 stops. About 18 percent of the time is spent idling (as in waiting for traffic lights). A short freeway driving segment is included in the test. The engine is initially started after being parked overnight.
The highway simulates a 10 mile trip with an average speed of 48 mph. The vehicle is started "hot" and there is very little idling and no stops.
Are the Label Estimates Calculated?
Fuel economy estimates are calculated from the emissions generated during the tests using a carbon balance equation. We know how much carbon is in the fuel, so by precisely measuring the carbon compounds expelled in the exhaust we can calculate the fuel economy.
After the vehicles have been tested, the results are adjusted downward to account for conditions that occur on the road that can affect fuel economy which don't occur during laboratory testing, such as cold temperature, aggressive driving, excessive use of power-hungry accessories, among others. The city is adjusted downward by 10 percent, and the highway by 22 percent.
The equation for calculating the city or highway average fuel economy, given in miles per gallon (mpg), is:
FEave = (total sales / [(sales1/FE1)+ (sales2/FE2) + ...+ (salesn/FEn)]
The calculation for combined fuel economy weights the city at 55 percent and the highway at 45 percent using the following equation:
FEcomb = 1 / (( .55 / city FE) + (.45 / hwy FE))
Vehicles are driven over identical driving patterns by professional drivers in controlled laboratory conditions on a dynamometer, which is like a treadmill for cars. The conditions that occur during driving, such as wind drag and inertia are accounted for on the dynamometer. There are two types of tests that are conducted: city and highway tests.
The city test is approximately 11 miles long and simulates a stop and go trip with an average speed of about 20 miles per hour (mph). The trip lasts 31 minutes and has 23 stops. About 18 percent of the time is spent idling (as in waiting for traffic lights). A short freeway driving segment is included in the test. The engine is initially started after being parked overnight.
The highway simulates a 10 mile trip with an average speed of 48 mph. The vehicle is started "hot" and there is very little idling and no stops.
Are the Label Estimates Calculated?
Fuel economy estimates are calculated from the emissions generated during the tests using a carbon balance equation. We know how much carbon is in the fuel, so by precisely measuring the carbon compounds expelled in the exhaust we can calculate the fuel economy.
After the vehicles have been tested, the results are adjusted downward to account for conditions that occur on the road that can affect fuel economy which don't occur during laboratory testing, such as cold temperature, aggressive driving, excessive use of power-hungry accessories, among others. The city is adjusted downward by 10 percent, and the highway by 22 percent.
The equation for calculating the city or highway average fuel economy, given in miles per gallon (mpg), is:
FEave = (total sales / [(sales1/FE1)+ (sales2/FE2) + ...+ (salesn/FEn)]
The calculation for combined fuel economy weights the city at 55 percent and the highway at 45 percent using the following equation:
FEcomb = 1 / (( .55 / city FE) + (.45 / hwy FE))
Part 600 – Fuel Economy of Motor Vehicles
___Good Luck
___Wayne R. Gerdes
___Waynegerdes@earthlink.net
#4
06-27-2005, 07:33 AM
Re: Interesting trip
The EPA testing revealed is interesting. In the real world, driving the way the tests simulate, I would be getting better mileage on the highway with my FEH (warm start and 48mph is ideal)!
I guess a lot comes into play when they make the mathematical adjustments after the tests are run, as the highway numbers take more of a hit.... and maybe the carbon-based testing somehow differs for hybrids (whose numbers might get a better boost from distance driven in EV mode than they do in the real world).
I guess a lot comes into play when they make the mathematical adjustments after the tests are run, as the highway numbers take more of a hit.... and maybe the carbon-based testing somehow differs for hybrids (whose numbers might get a better boost from distance driven in EV mode than they do in the real world).
#5
06-27-2005, 07:56 AM
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Re: Interesting trip
Originally Posted by sweetbeet
Coming back, however, I learned another thing - weight really does matter. We were loaded, with about 200 extra pounds of tools, furniture, etc., and traversing the same route in reverse (direction, not gear ), we only got about 29.2
), we only got about 29.2I do most of my driving alone but on occasion have to load up with a bunch of work equipment (2-300 pounds) plus the occasional passenger. I've never noticed a difference in performance or mileage with this small an increase in weight.
Maybe I'll start paying closer attention. If it does make a difference I'll have to start keeping the junk out of my ride.....
#6
06-27-2005, 10:19 AM
Re: Interesting trip
Well, it was pretty hot both ways, but hotter, I guess, coming back ("98 in the shade", literally). And, although we did use the A/C in both directions, we probably had it running a bit more coming back. So those things might have made a difference. I really can't think of anything else; I don't think there was a great deal of wind either day. There was more truck traffic going down, but I only tried drafting for about 10 minutes one time, just to see if I could detect any difference (until the saner? members of the family prevailed upon me - upon threat of banishment from the driver's seat 
- to cease such "reckless and dangerous behavior").
I am down to about "50 miles to empty" this morning (by the gauge; at "0 MTE" I have never put in more than 13.5 gallons, so I probably have closer to 80 or more when the gauge reads 50 MTE). I am going to fill up this afternoon or tomorrow morning, see what the calculated mileage is, and start over on a new tank to make sure I am "back to normal" and something weird hasn't happened to my car.
- to cease such "reckless and dangerous behavior").I am down to about "50 miles to empty" this morning (by the gauge; at "0 MTE" I have never put in more than 13.5 gallons, so I probably have closer to 80 or more when the gauge reads 50 MTE). I am going to fill up this afternoon or tomorrow morning, see what the calculated mileage is, and start over on a new tank to make sure I am "back to normal" and something weird hasn't happened to my car.
#7
06-27-2005, 10:45 AM
Re: Interesting trip
I gotta agree, I think there's some variables there that are making the bigger difference.
Subtle driving differences, traffic differences, and the big thing, road differences would probably account for 90+% of the difference in the MPG. Even just having more cars on the road around you can make a slight difference.
During my commute, I use the Southfield Freeway (Over 15 mile stretch); the road itself seems to be more fuel efficient going South than North; a slight lean coupled with just the way the road is.
I've made the same trip to my grandparents, once with just myself, and once with my parents, a grill, and a box full of stuff. Both had the Cruise Control set at the same speed, and were done on pretty much the same route. (I got off an exit earlier the second time because of construction.) There wasn't a difference in MPG going. Coming back was a different story, because I managed to draft for most of it the second time. (Averaging 40 mpg on the return trip!)
Subtle driving differences, traffic differences, and the big thing, road differences would probably account for 90+% of the difference in the MPG. Even just having more cars on the road around you can make a slight difference.
During my commute, I use the Southfield Freeway (Over 15 mile stretch); the road itself seems to be more fuel efficient going South than North; a slight lean coupled with just the way the road is.
I've made the same trip to my grandparents, once with just myself, and once with my parents, a grill, and a box full of stuff. Both had the Cruise Control set at the same speed, and were done on pretty much the same route. (I got off an exit earlier the second time because of construction.) There wasn't a difference in MPG going. Coming back was a different story, because I managed to draft for most of it the second time. (Averaging 40 mpg on the return trip!)
Last edited by Pravus Prime; 06-27-2005 at 10:47 AM.
#8
06-27-2005, 02:16 PM
Re: Interesting trip
Rich, I've been driving the freeways much more since I discovered drafting. I'm conducting test to find how to get the best MPG. Weight, wind direction, and wind speed all play a factor in MPG. I think the A/C is not as big a factor as I thought at high speed drafting (65-75 MPH). I found my MPG dropped below what I was getting without drafting in one test. If your going against the wind but its more of a cross wind on either side, drafting behind a big truck can hurt MPG do to turbulance. I found it helped a little when I moved to the next lane away from the wind side of the truck. Weight plays a lesser role but is a factor in my test at high speeds and wind problems.
The best way I found to get the best MPG is to control your right foot. A head wind makes you press the pedal harder and more often. Weight makes you press harder on the pedal to get to the speed you want as fast as you normally would (on ramp for example). If you can't back off the pedal a big deal while drafting, its not a good draft. A good draft would be between 38-48 MPG or better at 70-75 MPH, depending on a full load to just yourself. In a cross head wind, I dropped to 27 MPG with a near full load while drafting. I backed off and got 30 MPG without drafting.
I think wind is the biggest factor in MPG for highway driving. A tail wind can really help by itself.
Wouldn't it be nice to have a gage to warn your brain that your right foot is out of MPG control? Maybe a little tone that could be turned off if you did not want to hear it.
The best way I found to get the best MPG is to control your right foot. A head wind makes you press the pedal harder and more often. Weight makes you press harder on the pedal to get to the speed you want as fast as you normally would (on ramp for example). If you can't back off the pedal a big deal while drafting, its not a good draft. A good draft would be between 38-48 MPG or better at 70-75 MPH, depending on a full load to just yourself. In a cross head wind, I dropped to 27 MPG with a near full load while drafting. I backed off and got 30 MPG without drafting.
I think wind is the biggest factor in MPG for highway driving. A tail wind can really help by itself.
Wouldn't it be nice to have a gage to warn your brain that your right foot is out of MPG control? Maybe a little tone that could be turned off if you did not want to hear it.
#9
07-11-2005, 10:59 AM
Re: Interesting trip
I just got back from my first long roadtrip. 12 hours each way from San Francisco, up I-5 to Hood River, OR (about an hour northeast of Portland). Never ran the AC. Didn't hit any traffic. Averaged about 70 mph. Took it slow on the hills and coasted the downhills. We now have about 7200 miles on our FEH.
Average mpg? 22.7
I really need to start looking into the Lemon Law here in CA...
Average mpg? 22.7
I really need to start looking into the Lemon Law here in CA...
#10
07-11-2005, 11:36 AM
Re: Interesting trip
Cowboy,
Here is a weird thing to look at - A/C leaks. The A/C compressor is used to cool the air going into the battery in the back. If the Battery is too hot the system uses the ICE to run the A/C more cool the battery. If the A/C system is low on refridgerant then the copmputer will start the ICE to run the A/C compressor, but it will take alot longer to get cool air to the battery.
I point this out because I found an A/C leak in my FEH on Saturday in the lines that go to the battery pack. I topped it off with refridgerant Saturday and my MPG seems to have perked up a bit (although I could be wrong).
I get 27 MPG in fairly rough country in Mendocino County driving the FEH like a normal car (but keeping the speed down to 70 or so). 22 mpg going to Hood River seems unacceptable to me, unless you where towing a house trailer or dragging your feet.
Chris Brown
Here is a weird thing to look at - A/C leaks. The A/C compressor is used to cool the air going into the battery in the back. If the Battery is too hot the system uses the ICE to run the A/C more cool the battery. If the A/C system is low on refridgerant then the copmputer will start the ICE to run the A/C compressor, but it will take alot longer to get cool air to the battery.
I point this out because I found an A/C leak in my FEH on Saturday in the lines that go to the battery pack. I topped it off with refridgerant Saturday and my MPG seems to have perked up a bit (although I could be wrong).
I get 27 MPG in fairly rough country in Mendocino County driving the FEH like a normal car (but keeping the speed down to 70 or so). 22 mpg going to Hood River seems unacceptable to me, unless you where towing a house trailer or dragging your feet.
Chris Brown
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