OK, I'll bite. I'm a bit mystified that you are recommending a technique involving speeding (70-80 in 55-65 zones) in a thread about safe methods to improve fuel efficiency.

How did you deterrmine that this is:
(a) safe (or is it just the Lemming Principle?)
(b) fuel efficient (is the TCH somehow exempt from the laws of physics, specifically aerodynamics?)

You're certainly free to do whatever you want but it does seem a bit odd to post this here.

 

FYI John, I do not recommend speeding. If you read my post carefully you will notice that I also recommended losing speed gradually till you get back to the limit recommended by law (65mph). The main reason I suggest getting up to that speed is to calm "angry" motorists down for a while so that when you start losing speed they simply move to another lane without trying to harass you. Most of the time people zoom past me - even at 80 mph. When I get down to 65 mph, they are continuously zooming past me, cars, trucks, buses...you name it.

It is a well known fact that most drivers out there don't drive at the designated speed limit. My comment is to make it clear that you don't need to drive below speed limit (and endanger your precious life) to achieve high FE. Also, using CC might not be the best way either cos' it demands too much power going uphill and I just don't like entrusting my life to a computer...(I know the car is a "computer", but I like to take control of what I can).

I've driven on roads with posted speed limits of 55mph. and had people honking hysterically behind me just because I was doing 60mph.

I don't recommend speeding because it is unsafe and impractical (doing speeds over 80mph just burns gas faster without an equivalent rise in power output).

If you feel the need to do 20 mph below the limit just to achieve a 2% rise in FE and risk your life...be my guest. I just won't take such chances with so many impatient people out there.

My $.02

 

How about going the speed limit in your car, like I do in mine, a Prius and get better than the EPA estimates like I did on my last tank?
You certainly did advocate speeding by saying you get better FE by accellerating to 80 mph in a 55-65mph zone, that is at least 15mph over the limit. Not only that, you do it in a dangerous way, that is, you are either accellerating or decellerating, not driving a constant speed as all of the other traffic is likely doing.

As for driving 20 below the limit, I would never drive below the speed limit on a highway, that is nuts. You don't need to. 50-55mpg at 55mph (in my case, according to the bar graph on the MFD) is pleanty.

If someone is honking hysterically at you and putting you in danger because you are doing 60, the safest thing to do would be to let them pass and get them out of your life, because they are unstable, certainly do not speed up and keep them behind you where they can continue to put you in danger.

 

Take look at this thread:
https://www.greenhybrid.com/discuss/...-fe.14566.html
His data shows 42mpg at 70mph (like you) and 65mpg at 55mph, a difference of 54%, not 2%. And he's NOT going 20mph under the speed limit.
Do some testing and see what you get.

As for driving under the upper speed limit (the speed limit on I-95 here is 65max, 40min, so anything between is legal), I do it all the time (a year of commuting so far) and do not have problems. Generally 50-55mph. I agree that slower than 50mph people who aren't paying attention may not react quickly. Quite often (like yesterday) someone settles in a safe distance behind me and stays there for miles. I tried going 65 and, as you and scm2000 note, everyone passes you anyway.

Before you condemn this practice you should try it for a while. Ease into it by starting with speed limit for a week, then 5 under, etc, so you get used to people passing you. I was a bit nervous at first but got over it. Stay a bit to the right side of the right lane so they get a hint. Use hazard flashers for speeding trucks when they are well back to help them change lanes and whiz by. Let anyone merging on come in ahead of you. Monitor traffic in your mirrors and if the road is empty behind you, do whatever you want until the next clump catches you. I think you will find that it is not as dangerous as you think it is, and that as long as you drive in a predictable way you won't get molested.

I agree with scm2000 that the best way to deal with wackos is to help them by rather than spend time around them.

But hey if this is too scary for you then don't do it. Basically what you are doing is driving with load: constant load (mpg) on the engine rather than constant speed, which cruise control would do. Nothing wrong with that, it helps FE. Doing the same thing at lower speeds would yield higher FE.

 

Another consideration for highways is truck speed limits.

Often the truck limit is say 5-10mph lower than for other vehicles. I tend to run 60 in a 65 where truck limit is 55mph. Guess what, the trucks tend to run 60 anyhow, so they keep pace with me and provide a decent wind block

Yep, the test verified what I thought - anything over 60mph and my HCH2 FE nosedives.

 

Lightfoot: I know you are a very intelligent man/woman. However, I don't think the difference in FE while driving a TCH at those said speeds would be as high as 54%. Please take note that the vehicle mentioned in the article is a HCH2. The best FE I've heard of on a TCH (full tank that is) is about 51mpg (800 mile tank).

Your "apples to oranges" comparison sheds more light to the fact that you do not know what you are talking about. In all honesty, driving the TCH at 50-55 mph based on my experience tends to yield about 47-50mpg. At 65-70mph it tends to yield me about 42-45mpg. A considerable rise in FE (about 11 % if you take the upper limits), but nothing close to 54%. My daily commute is 55miles one way and I would not consider doing 55mph on the turnpike, unless if it is slowed by traffic (or speed limitations) or other adverse weather conditions. It would just take me too long to get there and my body would take an unnecessary hit daily(I already get up early enough to make it there).

spartybrutus: Trucks don't drive at the posted limit....maybe in your state but not in NJ. They drive at speeds of 70 mph and up.

scm2000: You still don't understand my post and I don't feel like explaining myself anymore. I am glad you enjoy your Prius, but your comment is sort of porous. How could you claim you get better than EPA estimates if you are only getting 50-55mpg ...Let me remind you that the OLD EPA estimate for the Prius is 60mpg. As for the TCH, the OLD EPA estimate is 40mpg....I am not trying to knock your car or act like I know it all. You have your techniques, I have mine. I still can't find any of your posts contributing to this thread, instead, your goal has been to deride my comments.

 

Hint: you already responded to me as "John" and it's in my sig (which makes me wonder if you're bothering to read).
You asserted, "If you feel the need to do 20 mph below the limit just to achieve a 2% rise in FE and risk your life...be my guest" when it's clear from my sig that I don't own a TCH. I was simply pointing out that the 2% figure is not generally true. I never said it would be as high as 54% for the TCH. That's why I suggested that you run some tests. Turns out you already have some data:
11% is not 2%

Actually I know exactly what I am talking about, both from a theoretical and a practical standpoint. My last tank in the Insight was 91mpg and the present one is at 95mpg with 2/3 gone. Sunday's 68 mile commute was 99.6mpg, today's was 90.9 thanks to the rain and wind. [This is not unbelievable: the winner of the Hybridfest Challenge drove from Washington State to Wisconsin at 50-55 and averaged 103mpg]. The old highway EPA on it is 66mpg. Applying similar methods to the Subaru has raised it from 24-25mpg (driving it at 80mph) to a high of 33.5mpg, and old highway EPA on it is 27. So I have a thorough grasp of what works and what doesn't, and slowing down works.

I know you've already made up your mind that this is unsafe and wastes your time, and that's fine. Just don't assert that the mpg gains of slowing down are negligible because they are not.

 

Im going to run the same tests on our Grand Caravan this week if possible. I expect that it will also show a significant FE % drop at speeds above 55mph.

Sorry about the NJ speeding trucks. Actually in Ohio the limit is often 55mph for them and most go 60mph. Those that go 70 tend to get picked off by the State Troopers

I have noticed trucks tending to drive slower this summer - all the better for wind blocks.

Also - 45-55mpg in a TCH doing 70-80mph?! That is pretty astounding as I expect my HCH2 to get 40mpg TOPs at those speeds.

 

It's also impressionistic -- when the estimate requires a 20%-wide range, it's definitely an *estimate*. And might be downhill. With a tailwind. Anyway, i wonder what the actual number is?

I've finally gotten to the point where I can sometimes get 55 mpg on a 25-mile commute that includes 19 miles of 72 mph interstate, in an HCH II, running light air conditioning, with a hint of tailwind. When I knock it back to 65, I get that FE consistently. If I were to knock it back to 55, I'd be getting 60 mpg, my sense is (from trying it in different segments from time to time).

By the way, in all this talk of speed limits, remember the maxes are different in the West -- we're pretty much all at 75 out here. In a 75, 55 *is* 20 under the limit, and of course, actual speed of traffic is 80-85.

As for trucks doing 70 . . . many companies limit their trucks to 65 -- which is why you hate to see one pulling out to pass someone in front of you -- unless you're driving a hybrid!

cheers --
doug

 

spartybrutus, I like your term "wind blocks". It's much more accurate and less inflammatory than "drafting", which the media tend to grab onto. I tried drafting trucks in the sense of driving straight behind them at close range and decided it was too dangerous for me besides being boring - and most trucks around here go too fast for me. I doubt that many people on this forum really "draft" up close behind trucks. But we all benefit from trucks breaking up the wind, especially headwinds [I was praying for semis while I was punching into the headwind yesterday and didn't get many]. So thanks, "wind blocks" is a much better term.