Please, before you start I know.
It's not big, clever or safe, I understand the risks to myself and other road users but given the right conditions.....
Well today east of Leeds on those deserted sections of the M62, M18, M180 and the A15 to a lesser extent I had a go.
220 miles in an Altea 2.0 Tdi DSG (auto), fuel computer calculated 60.8 mpg average.
It's a journey I've done may times and rarely bettered 50mpg, I did not pootle behind the 55mph bunch but selected European registered trucks who seemed to travel at 60-65.
It was a relaxing trip with speed adjusted to match with the cruise control and at a distance and road position where I could be seen by the other driver.
I did feel like I should be in a Maestro with cap and driving gloves at times sitting with the HGVs but as I watched I realised that a lot of them seemed to be at it as well.
So based on my simple, unscientific, on the hoof test I got a fuel saving of 20%.
Given the same conditions as today I'd do it again for the economy, the relaxing nature of a slightly lower speed and less lane changing.
The only reason I tried it was thanks to the Mythbusters team in the US, their results are after the link.
en.wikipedia.org/wiki/MythBusters_(season_5)#Drafting_For_Money
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"Well today east of Leeds on those deserted sections of the M62"
Hey you`re on my Manor ! trucks east of the M1 on the M62 are my personal suction devices.
I can get 78 MPG with my favourites, I`m working on getting a probe up their exhausts to power the engine on compressed exhaust gas. ;)
Regards
(sorry just joking, realised you`re a newish member;)
Edited by oilrag on 12/02/2008 at 21:39
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I`m working on getting a probe uptheir exhausts to power the engine
Oo-err missus.
Don't for pity's sake cross the border onto the East Yorkshire prarie's Seataltea as the outlaw Oilrag famous for being able to compose riddles so far removed from the comprehension of common man will be waiting for you, guns drawn and giving no quarter.
Please take heed this wanted man is not to be trifled with.
tee hee
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If you were far enough behind the truck to be able to see its mirrors, there's nothing wrong with what you did.
I have my suspicions about your choice of "virtual"car though; never known a Maestro to undertake a journey of that length without an AA Relay van being involved!
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.... Until you start crawling up a an incline at 40mph.
I think most of the efficency will be found if you were going downhill however when the throttle is left alone at 55mph.
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Done sensibly, as you appear to have, it provided fuel savings with a relaxing drive. When I did longer journeys it's how I tended to drive too. Driving at 55-65mph with some tow behind a large vehicle also affords a nice safety buffer - it's much easier to stop or lose speed (if necessary) at that speed & when all is said & done, I'd rather have an HGV in front & behind than an erratically driven repmobile. It's startling how much nervous & emotional energy you can use in the outer lane - lane 1 driving is my favourite if journeying anything over 100 miles or so. Leave the fun driving for A/B roads I say.
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If you were far enough behind the HGV to be seen in his mirrors, I would have thought you would be in the "dirty-air" (as they say on F1) and not in the slip-stream, how far behind aN "HGV" does the slip-stream effect operate?
Billy
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Irrespective of the slipstreaming, if you set your cruise to 60 mph and stick to it you will see dramatic improvement in your mpg without the risks.
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This raises one of my favorite questions!
If you wish to 'slipstream' surely the safest distance to the 'towing' vehicle is as close as is possible, provided there is nothing behind you? In the event that the lorry brakes, it brakes for you, there is zero diffential in speed as you contact the rear bumper, (ie zero damage), and most 40 ton vehicles will not have their braking performance degraded by the weight of your super mini.
However if the lorry snakes you are then in real trouble!
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If you were far enough behind the HGV to be seen in his mirrors I would have thought you would be in the "dirty-air" (as they say on F1) and not in the slip-stream >>
Agreed!
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>>and road position where I could be seen by the other driver<<
I thought the above line clinched it but for those for whom it didn't.
1. Roads are not straight, even Mways, think about your trigonometry.
2. To remain even within a few feet of the back of another vehicle you can be in the slipstream and still be visible in the mirrors, try it.
I was at at least 50ft from the back of the vehicles I followed and as a result of this I was visible, hence the term 'road position'.
It seems that at 100ft behind tests indicate an 11% fuel saving.
www.autobloggreen.com/2007/10/28/mythbusters-draft.../
Edited by seataltea on 13/02/2008 at 10:56
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and there's the other thing to think about; if you're chugging along with the trucks chances are there's one right behind you. Then when something goes awry you find yourself as the filling in an artic sandwich - a 40 tonner up your backside can spoil your day...
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I don't think the Op was really slotting between the convoys of trucks, he had found some foreign truck running unlawfully without a speed limiter (no change there then), so he hopefully didn't have a tailgater (if i did i'd be gone).
Have to say i don't personally like playing with the trucks and try my best to keep away from them whilst in a car, get fed up to the back teeth looking at the backs of trucks in me day job anyway.
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The slower speed makes a difference too. My old petrol Land Rover used to do about 19 mpg, but the best I got was about 24mpg when keeping to 50 mph, despite towing a trailer at the time!
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I used to have a petrol Landy too. The 3.5 V8. It would do about 15 mpg on a good day on 4 star. I could sort of live with its thirst while it was being used for dotting about locally but when I moved jobs and ended up with a weekly commute from Scotland to Cheshire it all got a bit silly on the cost front, not to mention the effect on my fillings! Great noise though. I used to try tucking up behind trucks for a pull along but it did feel rather dangerous in a car which took a bit of stopping at the best of times. It was replaced with a Granada 2.9 4/4 which was still "man enough" to pull the horse box we had at the time. It was never particularly abstemious on fuel either but by comparison with the Land Rover it was positively miserly at about 25-28 mpg. Oh for those heady days when you could fill a car like that for about £25! Having said that I can go further back and remember filling a Mk1 Cavalier for about £6. I'm sure some of the more...... em......experienced, backroomers can beat that though. I was interested to discover that the cruise control on my current car doesn't seem to contribute much to fuel economy. When I set myself the challenge ( I must get very bored on long journeys ) to beat it I can generally get about 5% better economy using good old fashioned "foot control". I'm sure someone will have a theory as to why this should be the case but the other thing which doesn't seem to have as much of an effect, if any, as I would have thought is weight on board. I use my diesel estate car for longish journeys most days, sometimes with it heavily laden and sometimes not, but it rarely varies much from 45-47 mpg. I suppose its because it gets taken up to cruising speed and then spends most of the journey in between 2-2.5 thousand rpm.
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So based on my simple unscientific on the hoof test I got a fuel saving of 20%.
Never mind the safety aspect for now - where does this 20% fuel saving actually come from?
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I don't know about the 20% figure, but the idea is that you gain by travelling in a local environment where the relative windspeed experienced by your car is lower than it would otherwise be.
i.e., the drag part of the road load is much reduced.
This reduction is not necessarily accompanied by a commensurate increase in the drag felt by the truck - it's even possible if you get close enough to reduce the drag on the truck by effectivley making the back end of the truck a more aerodynamic shape. Possibly a win-win.
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Yawn.
On German motorways they do it in trains of 15 repmobiles all doing 130mph 20 feet apart in the rain. Now that's slipstreaming, but I really don't fancy it.
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