After showing the new prius off to my friends and family it was time for a shake down trip before handing it over to my wife to a life of taking the kids to school and trips to the grocery store.

I headed to Tulsa OK from Houston. I ran the CC for the most part. 60mph @ ~50mpg, 65 mph @ ~48mpg, and 70 mph @ ~46 mpg. I'm happy!

I remebered reading about drafting on the forum and thought I would slip in behind a truck running 70 or so and see what it does for the FE. Wow 52 mpg at 70-72 mph behind the truck. Here is the issue with the draft. I had pulled in behind a refrigerated truck. It was dripping and I was getting some of it building up on my windshield. I thought it was just water from the refrigeration unit. While moving a little closer heading down a hill and maxxing the FE meter I noticed the liquid getting all over my brand new black prius was not condensation from the fridge but milk leaking out of the back of the truck. I tried to run the windshield wipers with washer fluid spraying and it would not take it off. I had to stop in Dallas and find a car wash open on Sunday to clean it up. It's now back to being gloss black.

I head from Tulsa to Dallas Monday and then back home to Houston on Tuesday. Then I hand the smart key over to my wife.

 

Drafting trucks is very dangerous. Yes, you'll increase your fuel economy, but you put yourself and the truck in a dangerous driving conditions.

 

If you are lucky, you will be tagging behind a big-rig on the rightmost lane going at the speed you wanted to cruise at for awhile. That does not happen often. If you are hypermiling, it probably won't happen as he will be doing 55-70mph, and you will be going no faster than 55mph.

I'd love to find out just how close you need to be to benefit from drafting (yes, I know it's so close you can't see around him...)

 

When I drive on the highway, this is my rule: I usually park the speedo at around 55 (of course allowing for decreases going up a hill/increases going back down), until a slow-enough big rig passes me and gets in front of me in the right lane. I think of this as "fishing"... just waiting at 55 mph for a suitable truck to pass me. If they're going 65 or less, I figure the benefit from drafting will outweigh the negative effect of driving at the increased speed (which, after all, comes from increased wind resistance that one would presumably be negating by drafting). So once the big rig passes me (not "flies by me" - then it wouldn't be a suitable target), I give 'er a little assist and slip into the wake envelope of the truck. I stay about 1.5 car lengths back. My mpgs invariably shoot up!

I've only recently started doing this, and it made a huge difference in my highway mileage (see my last few tanks, which admittedly aren't that impressive by true hypermiler standards). I can't wait for the summer to come back around, so I can really apply my newfound knowledge of hypermiling techniques and maybe get tanks in the 60s more often.

 

Very close. It depends on the size of the truck, but generally less than two car lengths. When you pull up behind the truck, you'll feel the car start to jump, when you're in the dirty air. As you get closer, the bufetting will stop and you'll be drafting.

Yes, I've done it. I'm not a saint. Not only can you not see around the truck, but he can't see you. There's no way to observe traffic ahead of you, to break if there's a problem.

 

Nice to know we got simular results. My drive was from Ft. Worth to Huntsville, AL, 818 mi., mostly on I-20 headed east. However, it was about 70 (F) for most of my route.

BTW, you may want to check: (1) tire pressure and (2) oil-overfill. The Toyota dealer had left the tires 'soft' and the oil overfilled.

The "Prius_Technical_Stuff" group had a discussion about drafting effects and one poster used an air-speed indicator to measure how far back the effect extends. You might Google for web pages about it.

GOOD LUCK!

Bob Wilson

 

as far as danger goes I expect I can out brake an 18 wheeler with no problem. I was getting decent FE increases @ 3 car lengths whike still partial in the buffet. But inside 2 lengths was best.

 

Are you sure? What if he brake-checks you? Truckers do it all the time, to drivers who draft them. They hate it.

You've done the experiment, as have I. Now it's time to move on. Drafting trucks is dangerous, illegal, selfish, and stupid. It's not worth putting people's lives at risk, to get a couple more MPG.

 

I ride a motorcycle most days. You car drivers with airbags and metal all around you don't know what dangerous is. But drafting is really just for fun and show and tell. It's too labor intensive to to keep up with the constantly changing speed of those big rigs. Not to mention the rock chips to the paint. But a 10% increase in FE in nothing to sneeze at. As far as illegal goes, there are no laws here in Texas about following distances. I guess we could say those that drive below the flow of traffic are selfsh to in there desire to get better FE. They back up traffic and could cause andaccident as everyone goes around them. Not to mention all those that tap their brakes to get the engines off....

So lets just stop calling others on the forum criminals, selfish, and stupid. It is really counter productive and the Green Hybid developer has asked that this type of trolling stop.

I never expected to get flamed on my 3rd thread after finally getting a hybrid.

 

I won't flame you but I want you alive and your car not damaged. I was drafting at night. Me very bad. The truck in front of me kicked up a shredded tire from the road and all I saw were the pieces flying past around me.

Got lucky that time, now I stay back.

DAS