What a Difference 10MPH Makes
When I started driving a car again following my stroke I knew I’d miss the stellar fuel economy of my now sold scooter. So I was deliberate in getting a used Toyota Corolla as they have among the best mileage for passenger cars save for the much more expensive Prius Hybrid.
I got quite a shock when I filled up the tank on 8/2/08 — the mileage was a disappointing 18.88. The city EPA for the car is 29mpg. I was pretty sure nothing was wrong with my car. The prior fill-up had been on 7/14/08 and I had only driven 202 miles. My city driving is bad for mileage and wear & tear on the car. My trips are frequent and short.
So yesterday I drove back to Oklahoma City to visit family. I filled up the tank again on Wednesday so it would be full when I left. For that week between getting gas I drove just 50 miles. This time I managed to improve to 20.597mpg.
The drive to OKC is 500 miles. I decided to use the trip to experiment a bit. Leaving St Louis early Thursday morning I set the cruise on 60mph. This felt comfortable to me as I’m still getting used to highway driving with one hand on the wheel. In Joplin I filled up again even though I had a half of a tank left. The mileage over those 300 miles was an outstanding 43.958mpg! That was with the A/C running too.
I knew when I got to Oklahoma I’d pick up the pace a bit. While the speed limit on I-44 in Missouri is 70nph in Oklahoma it is 75mph. Many drive faster, I know I usually did in the past. So when I left Joplin I through caution to the wind and kicked it up to 70mph. By this point I was very comfortable with my highway driving and was looking at the clock and thinking how slow it was going.
When I pulled off the highway in Oklahoma City I immediately got gas again. The extra speed had taken its toll, I got “only” 32.143mpg. Lots of people would kill for highway mileage in the 30s but compared to the mileage on the first leg of the trip it was a let down. That extra 10mph made a huge difference.
Perhaps we should lower highway speed limits again?
The time difference for my trip is just over an hour. I made more stops than in prior trips just to rest and to stretch. It took me 12 hours to do what I used to do in 7. Typical of my post-stroke life, everything takes longer. On my return trip next week I may just take it easy, stop off in Tulsa to see a couple of things and spend a night in Springfield or thereabouts.
The fuel savings from driving 60 the entire distance would be about five gallons, less than 20 bucks. A cheap room along the way will certainly cost more than that. Maybe we shouldn’t lower the speed limits, allowing people to decide for themselves what is the best speed/time/mileage ratio for themselves? I do think if more people knew the potential savings we’d see a natural reduction in travel speeds.
But that isn’t going to help my city mileage. All the short trips, lots of stop signs and poorly timed traffic signals are just not ideal conditions for conventional cars. Hybrid’s with regenerative braking thrive in these conditions — getting extra juice from all those braking moments. For now I’ll just try to keep my driving to a minimum and use my plug-in electric (power wheelchair) for those local trips.
Didn’t you mean 100 mp G? Anywho- I think besides fuel economy, another issue with the speed limit is the difference between the slow cars and the fast ones. A large disparity is more likely to cause an accident as people try to get around those who prefer to drive 50 MPH on the toll road while others are doing their standard 10mph (speeding) over which in this case would be 80mph. I too travelled alot in the last 4 days as I racked up around 900 miles. I have yet to figure out what my mileage was, but I have the receipts and I know the total distance so I will respond again for my average. Most of it was highway miles and most of it was at around 70 to 80 mph in a Jeep Compass with a CVT transmission. The only thing good about it was that I felt like I was driving a larger car, but the fill up was only about $37 from empty to full so I think it had pretty good fuel economy.
On a side note- while in the middle of kansas I saw this car that looked like a Smart car, but it had a hatch on the back where someone in a wheelchair can roll up into it from the rear, lock in place and go. Awesome invention. Check it out.. http://www.kengurucars.com/
OK, my bad- I thought I saw another 0 in your title.
“Filling” the tank completely is difficult to do in cars with modern evaporative emission controls. The most accurate mileage numbers are the averages calculated over multiple tanks, not those of just one tank, especially one with less than 10 gallons. So far, it looks like you’ve averaged 28.63 mpg (773 miles/27 gallons), which ain’t too shabby . . . it’ll be interesting to see how more highway miles improve your number.
[slp — I think the trick is to be consistent. I lock the pump and when it shuts off I’m done. In places like Joplin and Oklahoma City they don’t have evaporative stuff on the pump handles like bigger areas like St Louis. The application on my iPhone is neat as is shows the mpg on the last fillup and an average (see image).]
Those are some very impressive numbers for your fuel economy. Without even trying any of the other ‘hypermiling’ techniques out there, you managed to increase your fuel economy by 10 mpg. Nice job.
I think most people know that if you just slow down a little bit, you get better fuel efficiency. But if everyone else is traveling at 70-75, it’s hard to feel comfortable driving 65 (or less).
Most drivers are closer to 80 mph, many over 90, in 65 mph zones. Our mpg has much to do with speed but also wind, weight, even tire pressure. The EPA data remains exaggerated and I get a good laugh when big SUV drivers emphatically claim that they average 19 mpg. You made it safely, that what counts.
Speed restrictions were a failure (the driving public overwhelmingly rejected it) so why should it be imposed again. Just went over 500mph today at 75mph and that was the max for most on the road. It’s safe and convenient (i.e. a time saver) at that speed.
We don’t need a return to failed policies. We have gained more significantly from technology improvements then attempts to modify behavior.
Lastly, please refer to my prescient observations of several weeks ago about the price of oil. Down to $115 today on its way to below $80. Gees, $60 seems like a fair value right now. Just had to blow that horn, sorry!
I think we should go fast as hell on the highways. Trucks especially should be allowed to go 110 miles and hour or faster. The National death toll would probably only rise by 10,000 a year or so. That’s a small price to pay for handsome corporate profits and a continually rising stock market don’t you think?
After all the free market system should include highway speeds also, why have any regulations at all? The rape of America should continue until it is exhausted. Steve, your problem is that you have put energy conservation ahead of corporate profits, obviously you have lost your flag lapel pin.
The GF and I just took trip east over mostly federal Interstates. I drive a ’98 VW Passat, which has 130,000 miles on it. My average fuel economy was between 36mpg and 38mpg, according to both my trip computer and actual miles travelled v. gas taken at the next fuel station. This is all with a manual transmission and driving between 65-75mph. I employed some of the so-called hypermileage techniques, but the majority of the time topography didn’t always lend itself to coasting. As for feeling “safe”, I have never, since I began driving 55-60 around town on highways and Interstates and the higher speeds on cross-country trips, felt unsafe. As long as I maintain control of my own actions and remain vigilant with regards to the other(idiot speeding drivers)motorists, I will do well. Tail-gaters, etc., only annoy me. I usually slow down or tap the brakes(yeah, I know, not necessarily safe itself)to get the morons off my ass. Usually works. BTW, I do not, repeat, do not, drive in any other lanes but the right one when I am driving at these speeds. Frankly, I don’t know why anyone would drive faster than I do, considering that a large potion of our gas dollars go to countries which, directly or indirectly, often sponsor/fund um, ahem, “extra-governmental” military organisations. Plus, I am of the opinion that the oil corp(se) and other energy producers would love nothing better than to maintain their stranglehold on our transpotation choices. Why should I fund that? I mean really, folks, this country doesn’t make as much money as it once did, and every dollar we send overseas leads us further into national penury. Ya’ wanna blow your wad on the Saudis and the Emirates, etc., go for it.
I just did another one of my “Mom” trips, to Louisville in our 2002 Mazda Protege 5. Setting the cruise at 8 mph over the posted speed got me 24.6 mpg and I was passed by very few people on the way over (john, most folks ARE driving more slowly out on the open roads, even without any change in the posted limits). On the way back, I set the cruise at 3 over, and got 27.0 mpg, and was passed by more people, but not that many more. I also averaged 20 mpg for the around-town stuff in Louisville – not bragging, just reality.
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Conclusions – one, people are driving more slowly. Two, speed matters, but there’s a distinct trade-off in time versus money. There’s also a trade-off in money veresus money – gas is 20 cents a gallon more expensive in Louiville than here, so the gallon I saved driving back only netted me $1.50. Three, time got thrown out of the equation – I was stuck in trafffic outside Mt. Vernon for 45 minutes due to paving, so the return trip that took, what, 15 minutes longer in actual driving time, actually it was slightly quicker due to fewer delays. Four, the biggest impediment to driving smoothly, in Illinois especially, are lower speeds for trucks. The best thing for fuel economy is to put it on cruise and leave it alone, but every time you have to slow down for one semi passing another, you burn a little bit more as you get back up to speed. And five, weight matters. Steve’s Corolla is probably 200 pounds lighter than the Protege.
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Bottom line, this is an interesting academic exercise, but it’s all realtive – my best time between here and there has been 3½ hours; the trip back yesterday, without delays, took slightly more than 4 hours. On the quicker trips, I probably get 22-23 mpg – is the the extra $4-$6 I’d pay for gas a burden if I can get there a half hour quicker? No, not at all – I can make that up by having one less beer or I can “pay” for half my gas by staying at the Microtel instead of the Hampton Inn. It’s all about choices. We all “should” do what we can to save fuel, but how much should the government be involved? It’s also my money, and if I want to “waste” it by driving faster (so I can get to bed a half hour earlier), that’s MY choice.
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Our next car will be a Prius (wife’s decision). We’ll be saving money on gas every day, but we’d save even more money if we bought a Corolla or a Yaris or an Aveo or a Civic or a Smart for two or any other cheap, small non-hybrid that gets 30+ mpg – the capital cost of the Prius is simply too high to recover it in fuel savings, but it is a bigger and nicer car than any of the cheaper ones. Again, it’s a choice (as would be a Hummer or a Wrangler or a Dodge Ram). Part of working hard and doing well is being rewarded for your efforts. Few people buy a vehicle not having a clue what kind of fuel mileage to expect, and if they do, they deserve what they get – the information and the options are out there. And as the general said after Katrina, “You can’t fix stupid”!
Your experiment was a little flawed.
You don’t have enough data to suggest that the 11mpg drop in performance was entirely(or even primarily) due to the reduction of your speed. I suspect having the wind blowing “against” you for one leg of your trip and blowing “with” you on the return leg had far more to do with your mpg than the 10mph speed reduction did. With modern transmissions, you don’t see stark differences in mpg at higher speeds.
To do this experiment properly, you need two identical cars(one being used as a “control” car) to make the trips side by side both ways. You then need to compare the data between those two cars to come to a conclusion on how great of an effect the 10mph drop in speed has on fuel economy.
Even with the above change, the experiment still isn’t the best because the cars will experience different wind conditions increasingly as they get further and further apart.
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Ideally to do this properly, you’d need a wind tunnel to hold constant wind conditions.
While this has a definite commercial purpose, it’s still kinda cute and fun: http://www.carfunfootprint.com/
Short memories: http://www.post-gazette.com/pg/08235/906137-185.stm