Saturday, June 02, 2007

Drive Slower, Save Fuel

Back in October Bean-Sprouts challenged readers to keep their car tyres inflated to save fuel. But it turned out that, despite all the "tips" telling you to do just that, tyre pressure makes no appreciable difference to fuel economy., who manage's automotive websites, tested the tips and found out what really works. I was delighted to learn that air conditioning makes no appreciable difference either. Hurrah!

So what does make a difference to car fuel economy? Well, accelerating gently, driving slower and turning off the engine when stationary for more than a minute. So this June the challenge is to drive slower to save fuel.
How much slower? I'm going to leave that up to you. If you tend to drive at "speed limit plus ten", you might try driving at the speed limit. It could save more than money - it might save your license or even your life. If you tend to stick to the speed limit, you could try driving at "speed limit minus ten percent". It's up to you.
Don't forget to vote in the poll in the right-hand sidebar.


Unknown said...

Aircon makes no difference? Really? Have you got a link to that Mel - it'd be splendid news... sounds too good to be true though.

Regarding the speed thing, I don't doubt it for a minute. The trouble is, there's a trade-off between speed and safety unless you've got the road to yourself; if you try to travel at slower-than-average speeds then other road users begin to want to get past you.

It's important to realize that the tests on speed vs efficiency are conducted on race tracks, in top gear. As a matter of fact the "sweet spot" for fuel efficiency is somewhere between 40mph and 60mph depending on your engine and driving conditions, so pootling along at 25mph in a 30mph zone is actually less efficient than driving at 30mph, unless the extra speed is making you brake and accelerate more!

Melanie Rimmer said...

All the data are from
The tests were conducted on real roads, but they weren't repeated. For scientific accuracy I'd want to see the tests conducted several times, with a variety of different cars, and averages taken. But I can't find such a study so this is the best I can do.

Anonymous said...

I'd also want to see the tests done over the period of a year (differing weather / temperature conditions), I see a significant (4-8 mpg) difference between winter and summer.

Wulf said...

Gosh, Mel, your blog must be widely read. I sat behind several people yesterday afternoon who were going at speed limit - 10% or even speed limit - 30% driving through the streets of London on my way to and from a gig! ;-)

As I understand it, fuel usage is dependent on how hard the engine works, which is measured by the RPM meter; my present car (a very compact and efficient Daihatsu Cuore) has one of these on the dashboard. Somewhere hanging below 2K rpms seems to be about right as the level that gives enough energy to keep the engine going smoothly driving round town. Having the meter allows me to check that against road conditions (eg. incline) and find the appropriate gear.

Unknown said...

I did a bit more reading on the A/C thing Mel - going to the USA since they have more experience of it. (

It seems that A/C reduces your cruising economy by about 1 or 2mpg, about the same as having your windows open - not too important at speeds, but a big difference when idling.

It's worth mentioning that it is, indeed, hardly significant when compared to such biggies as staying off the damned breaks, driving sensibly, and not tailgating the Hedgewizard. He hates it, yes he does!

Anonymous said...

I had read I think on, not 100% sure, that you should not accelerate too slowly either. You shouldnt let your pedals hit the floor, but not accelerate too slowly either.

Anonymous said...

Hedgewizard is quite correct, Mel. Using Aircon DOES make a substantial difference according to all of the studies that I've seen, of anything up to 10 to 20%, however this is exactly the same as the drag induced increase that opening your windows causes. At motorway speeds air con is more efficient than windows though.

The trick, therefore, seems to be to only use your aircon when it's strictly necessary, not as an automatic habit (which, living in good old blighty should be at most 3 days a year...).

You are spot on, though, about keeping to the speed limit. Driving at 75 rather than 65mph damages fuel economy by over 10%.

As Hedgewizard points out, driving smoothly is also key point.


She Who Digs said...

Hi Mel,
As well as overall speed, it’s how you get up to speed, which can alter your fuel efficiency. My DH accelerates away much harder that I do which is why I can get more MPG from our Toyota Prius than he can, but I’m sure is the same for other non-hybrid cars too. (I’ve turned this into a private competition with him!) I’ve found that keeping the tires inflated helps too, along with not driving with the windows open! This causes the aerodynamics to be interrupted- (and makes a horrible noise) and is true of any car, particularly if you’ve also got a roof rack or box attached. I don’t know how open windows vs. air-con measures up in fuel terms, but maybe adjusting the temperature by only a few degrees, like what is promoted with home heating thermostats, could still make a difference! There is so much information out there it’s so hard to know what to believe but I do agree with you that if everyone were to do just a little, the world would be greener for it! Love your blog- how do you find the time for everything? SWDx

Anonymous said...

Ooops, posted my comment to the old blog entry. Re-entered here, with some spelling corrections :) -

I am struggling to believe that A/C makes no difference, though I notice they seem to have only tested with A/C on, or with windows down. Also this is USA based research where the engines are much bigger.

I can feel the speed difference that A/C makes on my 1.25 Fiesta, so I would think it has to be equivalent to at least a couple mph.

I try to use the windows at slow speed and the air-con if absolutely needed only at high speed.

I should probably drive less aggressively and fast but it's a hard habit to break. Easy to just use alternative transport wherever I can.

Anonymous said...

成人電影,情色,本土自拍, 美女交友, 嘟嘟成人網, 成人貼圖, 成人電影, A片, 豆豆聊天室, 聊天室, UT聊天室, 尋夢園聊天室, 男同志聊天室, UT男同志聊天室, 聊天室尋夢園, 080聊天室, 080苗栗人聊天室, 6K聊天室, 女同志聊天室, 小高聊天室, 情色論壇, 色情網站, 成人網站, 成人論壇, 免費A片, 上班族聊天室, 成人聊天室, 成人小說, 微風成人區, 色美媚部落格, 成人文章, 成人圖片區, 免費成人影片, 成人論壇, 情色聊天室, 寄情築園小遊戲, AV女優,成人電影,情色,本土自拍, A片下載, 日本A片, 麗的色遊戲, 色色網, ,嘟嘟情人色網, 色情網站, 成人網站, 正妹牆, 正妹百人斬, aio,伊莉, 伊莉討論區, 成人遊戲, 成人影城,
ut聊天室, 免費A片, AV女優, 美女視訊, 情色交友, 免費AV, 色情網站, 辣妹視訊, 美女交友, 色情影片 成人影片, 成人網站, A片,H漫, 18成人, 成人圖片, 成人漫畫, 情色網, 日本A片, 愛情公寓, 情色, 舊情人, 情色貼圖, 情色文學, 情色交友, 色情聊天室, 色情小說, 一葉情貼圖片區, 情色小說, 色情, 色情遊戲, 情色視訊, 情色電影, aio交友愛情館, 色情a片, 一夜情, 辣妹視訊, 視訊聊天室, 免費視訊聊天, 免費視訊, 視訊, 視訊美女, 美女視訊, 視訊交友, 視訊聊天, 免費視訊聊天室, 情人視訊網影音視訊聊天室, 視訊交友90739, 成人影片, 成人交友, 本土自拍, 免費A片下載, 性愛,
成人交友, 嘟嘟成人網, 成人電影, 成人, 成人貼圖, 成人小說, 成人文章, 成人圖片區, 免費成人影片, 成人遊戲, 微風成人, 愛情公寓, 情色, 情色貼圖, 情色文學, 做愛, 色情聊天室, 色情小說, 一葉情貼圖片區, 情色小說, 色情, 寄情築園小遊戲, 色情遊戲情色視訊, 情色電影, aio交友愛情館, 言情小說, 愛情小說, 色情A片, 情色論壇, 色情影片, 視訊聊天室, 免費視訊聊天, 免費視訊, 視訊美女, 視訊交友, 視訊聊天, 免費視訊聊天室, a片下載, aV, av片, A漫, av dvd, av成人網, 聊天室, 成人論壇, 本土自拍, 自拍, A片,成人電影,情色,本土自拍,

Anonymous said...

情色電影, aio交友愛情館, 言情小說, 愛情小說, 色情A片, 情色論壇, 色情影片, 視訊聊天室, 免費視訊聊天, 免費視訊, 視訊美女, 視訊交友, ut聊天室, 視訊聊天, 免費視訊聊天室, a片下載, av片, A漫, av dvd, av成人網, 聊天室, 成人論壇, 本土自拍, 自拍, A片, 愛情公寓, 情色, 舊情人, 情色貼圖, 情色文學, 情色交友, 色情聊天室, 色情小說, 一葉情貼圖片區, 情色小說, 色情, 色情遊戲, 情色視訊, 情色電影, aio交友愛情館, 色情a片, 一夜情, 辣妹視訊, 視訊聊天室, 免費視訊聊天, 免費視訊, 視訊, 視訊美女, 美女視訊, 視訊交友, 視訊聊天, 免費視訊聊天室, 情人視訊網, 影音視訊聊天室, 視訊交友90739, 成人影片, 成人交友,

免費A片, 本土自拍, AV女優, 美女視訊, 情色交友, 免費AV, 色情網站, 辣妹視訊, 美女交友, 色情影片, 成人影片, 成人網站, A片,H漫, 18成人, 成人圖片, 成人漫畫, 情色網, 日本A片, 免費A片下載, 性愛, 成人交友, 嘟嘟成人網, 成人電影, 成人, 成人貼圖, 成人小說, 成人文章, 成人圖片區, 免費成人影片, 成人遊戲, 微風成人, 愛情公寓, 情色, 情色貼圖, 情色文學, 做愛, 色情聊天室, 色情小說, 一葉情貼圖片區, 情色小說, 色情, 寄情築園小遊戲, 色情遊戲, 情色視訊,

Anonymous said...

aaaa片, 免費聊天, 咆哮小老鼠影片分享區, 金瓶梅影片, av女優王國, 78論壇, 女同聊天室, 熟女貼圖, 1069壞朋友論壇gay, 淫蕩少女總部, 日本情色派, 平水相逢, 黑澀會美眉無名, 網路小說免費看, 999東洋成人, 免費視訊聊天, 情色電影分享區, 9k躺伯虎聊天室, 傑克論壇, 日本女星杉本彩寫真, 自拍電影免費下載, a片論壇, 情色短片試看, 素人自拍寫真,

做愛的漫畫圖片, 情色電影分享區, 做愛ㄉ影片, 丁字褲美女寫真, 色美眉, 自拍俱樂部首頁, 日本偷自拍圖片, 色情做愛影片, 情色貼圖區, 八國聯軍情色網, 免費線上a片, 淫蕩女孩自拍, 美國a片, 都都成人站, 色情自拍, 本土自拍照片, 熊貓貼圖區, 色情影片, 5278影片網, 脫星寫真圖片, 粉喵聊天室, 金瓶梅18, sex888影片分享區, 1007視訊, 雙贏論壇, 爆爆爽a片免費看, 天堂私服論壇, 情色電影下載, 成人短片, 麗的線上情色小遊戲, 情色動畫免費下載, 日本女優, 小說論壇, 777成人區, showlive影音聊天網, 聊天室尋夢園, 義大利女星寫真集, 韓國a片, 熟女人妻援交, 0204成人, 性感內衣模特兒, 影片, 情色卡通, 85cc免費影城85cc, 本土自拍照片, 成人漫畫區, 18禁, 情人節阿性,

免費成人影音, 彩虹自拍, 小魔女貼影片, 自拍裸體寫真, 禿頭俱樂部, 環球av影音城, 學生色情聊天室, 視訊美女, 辣妹情色圖, 性感卡通美女圖片, 影音, 情色照片 做愛, hilive tv , 忘年之交聊天室, 制服美女, 性感辣妹, ut 女同聊天室, 淫蕩自拍, 處女貼圖貼片區, 聊天ukiss tw, 亞亞成人館, 777成人, 秋瓷炫裸體寫真, 淫蕩天使貼圖, 十八禁成人影音, 禁地論壇, 洪爺淫蕩自拍, 秘書自拍圖片,

eda said...