Archives

Hi all,

Looks like I'll be packing up the wife, 2 kids, and probably lots of junk to head to the beach this w/e. Raleigh to Myrtle = about 4 hours of mostly flat highway driving (a good deal of I-95). Considering I've honed my HMing on country roads and small stretches of highway, I'm curious what I need to think about before and while on vacation that might differ from my commute. We'll be taking the Montero Sport. I suppose it all starts with tire pressure.... (Oh, and there will be no FASsing. But I'm open to P&G the whole way with NICE-ON if that won't mess up the tranny.)

I've never driven a mitsu before, so bear that in mind while reading my tips.

I've seen upwards of 30mpg in my Odyssey (old epa 18/25) by simply feathering the throttle in the 50-60mph range. Wayne does similar in his MDX, which has the same platform. 50 is better, of course. ;) Wayne has a picture up somewhere of 37 in his MDX.

The trick is to get it into top gear, let that lock up, and then maintain just above that point. With smaller rises in the terrain, give a little push before arriving, so you can carry enough speed up and over and still stay locked in top gear.

Another option is a very slow, very long P&G-like cycle. Get up to 60mph (just an example), and then let up on the throttle a hair. Then let up another hair. Keep letting up until you're losing speed at no more than 1-2mph over a quarter mile. After 1/4-1/2 mile of that, ease into the throttle again (maybe 3-4 tps higher) and over another 1/4-1/2 mile regain the speed. Rinse & repeat.

I've never driven a mitsu before, so bear that in mind while reading my tips.

I've seen upwards of 30mpg in my Odyssey (old epa 18/25) by simply feathering the throttle in the 50-60mph range. Wayne does similar in his MDX, which has the same platform. 50 is better, of course. ;) Wayne has a picture up somewhere of 37 in his MDX.

The trick is to get it into top gear, let that lock up, and then maintain just above that point. With smaller rises in the terrain, give a little push before arriving, so you can carry enough speed up and over and still stay locked in top gear.

Another option is a very slow, very long P&G-like cycle. Get up to 60mph (just an example), and then let up on the throttle a hair. Then let up another hair. Keep letting up until you're losing speed at no more than 1-2mph over a quarter mile. After 1/4-1/2 mile of that, ease into the throttle again (maybe 3-4 tps higher) and over another 1/4-1/2 mile regain the speed. Rinse & repeat.

Super-helpful. With an old hwy EPA 22, I've got my work cut out for me getting anywhere near 30 with a loaded car. The DWL regime I think I can do without too much trouble. In this boat, I'd probably do best somewhere around 40 MPH, but I think the family doesn't want it to take a day to get there.

As for the P&G, why would your DWL-like cycle be better than a typical highLOD/NICE-ON cycle? Of course, I wouldn't want her to downshift on me, but in my limited experience with the car, I've been able to keep it in top gear over 30MPH by just being careful. As I'm sure you know, you can kind of sense when the tranny is thinking about downshifting. I dunno what it is, but I just feel it and step back from the precipice.

I'm not completely sure, and I would need more testing to say for sure. I've seen similar results with both. One thing is for sure, though: family and friends accept the smooth and light approach to any kind of heavy P&G.

On long trips I just pressure up the tires-42 ft 46 rear ,use syn oil ,use syn diff lube ,and use the Cruise control to set whatever speed you want. It is tough to P&G over long trips ,so I just D/C the CC on hills, and I use the CC to speed up rather than my foot.

Don't put anything on the roof of course.

P&G is pretty tiring over long distances, so you might just try to set the CC at a lower-but reasonable -speed -say 55 mph or so. The 98 Suburban gets 21 mpg at 68 mph on CC, the"new" EPA is 17 hy , so it beats it by 4 mpg. Your Montero must "new" EPA at 20 mpg or so,so it should get 23-24 mpg at 65 mph and maybe 26-27 mpg at 55 mph.

I leave the scangauge home on long trips ,so I can concentrate on driving and fiddling with the XM radio.

It would be interesting to see what you would get just using the CC, and d/cing it for hills. Lot less tiring.

You might want to make sure your oil is just 1/4 the way up the stick range- but most folks don't want to full around draining tiny amounts of oil before trips.

I suspect -not much proof - that the CC i with d/cing for hills is within 5% of P&Ging at highway speed averages on long trips. I remember WG and company got ~56mpg with the Prius on that long trip from Chicago to CA in the "battle" with the Honda Diesel. In general the Prius would get 50 mpg with the CC on ,and theses guys are the best of the best at p&g. Lesser hypermilers -most of us- wouldn't get 56 mpg on that trip while P&G . Of course there was lots of wind on the trip ,and the Prius isn't a typical car.

It is a lot easier to set the CC on long trips.Interesting to see how it would do.

Luck,
Charlie

Within this context, steady speed (CC or with your foot) should give similar results. If you go read Tarabell's article about the HCH-II, you see that the foot vs CC results converge as speeds get higher.

In the other corner sits my Civic, with its manual trans and super-short gearing. P&G is the only way to get good highway mileage out of it. I can get 50 mpg at 50 mph, or P&G with the same 50 average speed and get 65mpg.

Palemelanesian- makes sense ,as the speed increases the percent of propulsive power lost to aero drag increases ,and the savings from engine friction-reason P&G works- will be less since it has to be on more. P&G was custom made for FSPs in city driving - no pint in wasting all that momentum, but not so great at constant high speed.In general the OEM engineers do a pretty good job if you jack up the tires etc.

The CC is better FE wise than my rt foot ,so I use it constantly. On very long trips I don't even shut it off for hills because I get tired.

It would be interesting to develope some data on the FE of vehicles on long trips at various speeds with the CC on. Someday soon I'll be doing a 700 mile trip at 62 mph with the CC on.I'm curious how that will compare to 68 mph. I'm not so sure my Suburban will get better mpg at 45 mph than at 60 mph. It should ,since it is locked up about 45 mph, but my scangauge doesn't indicate that on short-4 mile-city interstate legs.

Charlie

I wonder if your gears are set to lower rpm than mine.

Past trips show the following on my Oddy, with cruise set:
70mph (2100 rpm): 25mpg
65mph (1950 rpm): 27mpg
60mph (1750 rpm): 29mpg
55mph (1600 rpm): 30mpg

I've only done shorter legs at lower than 55, but I have seen 32mpg on occasion.

Abndrew -thanks for the info.

Your odyssey uses 83% of the fuel at 55 mph that it uses at 70 mph ,or it goes 20% farther on the same amount of fuel.
My crude calculations indicate that you have 1.6 times the drag at 70 mph that you do at 55 mph. If your 50/50 point was 55 mph them you would expect to use about 2/2.6 or 77% as much fuel at 55 as at 70 mph.

I think this indicates that the Odyssey is pretty aero and it probably doesn't use as much aero fuel as rr fuel until it hits maybe 62 mph or so.

My Suburban is actually geared kinda low relative to our Pilot.It turns about 1725 RPMS at 60 mph and 2000 RPMs at 70mph,the Pilot would turn about 1650 RPMs at 60 mph.
My Titan was geared tall- 1525 RPMs at 60 mph.It didn't turn 2000 RPMs until it hit 80 mph.The Titan had decent FE-about 20 mpg same trips/speed as the Suburban , but I used standard tire pressure then-not sure just how much the 8 psi over "stock" is worth.My tires are also at least 50% worn-that helps.
Another point that I have my doubts about- the Suburban has lots of engine wear-I guess - since it has 205,600 miles-My mechanic buddy suggests that my "loose engine" has burmished itself and has low internal friction. Ok I buy some of that , but usually high miles means poorer FE -ring wear etc. It uses 1 qt per 3000 miles-syn 5w30 -more than a new, modern motor would, but not really "out of range".

Frankly, I don't know why the Suburban does so well. I think the odometer is 1% high,so that drops it to 21.1 mpg -still too good for almost 70 mph. The speedometer might be 3 mph high at 70 mph , but 21.1 mpg at 66 mph is still seems "too good" in comparison to what other Suburban drivers report.

My guess is that they-other drivers -drive faster than they think they do- maybe doing 74-75 mph when they think they are doing"about 70 mph" They also probably don't check their tires, and run under the "door" psi and way under the 42-47 psi I use.
The 2000 on Suburbans use 265/70 16 tires vs 235/75 15 tires - another FE negative.

None of them are geared "tall" the most common diff is a 3.7(with taller tires) -giving about the same rpms at 60 mph that my 3.4 does.

I'm kinda puzzled it does so well-I expected 17 mpg at 65-70 mph.The short city interstate jaunts (4 miles)I did with the scangauge indicated just that 4.8m/lt at 70 mph.

Can't complain really .I'll eventually use DOUBLE layers of aluminum flashing to seal the bottom and see how that improves the FE.It is easy to work with and cheap.I'll glue the layers together to make them stiff enough.

Thanks,
Charlie
PS I would love to see some other Suburban figures-the 2004 is rated 1 mpg better hy,and the 2007 is rated 3 mpg better.This means the 2007 should get about 25 mpg at 60-65 mph?? I don't see any claims of that , but WG got awfuly good mpg with the Hybrid Tahoe in his Hy driving-35-40 I think.
PPS I've noticed that the Sienna's nose looks a lot like the Prius's nose-which looks a lot like the Odyssey's nose-no surprise there I guess -wind tunnels give about the same answers no matter who is doing the "asking"

Thanks for those calculations. I'll have to ponder them a while now. ;)

Hi all,

Well, I loaded up the FSP on Friday with lots of heavy stuff. Not sure what the total added trunk weight was, but I would have to guess it was about 200 lbs.

I'm still waiting for my replacement SGii connector so I was flying blind.

As for the tires, the door jamb says 26/32 (front/back), the sidewalls say 44/36 (front/back), and I decided to do 32/36 (front/back) for the trip. I wanted to maintain higher pressure in the back because of the weight distribution, but didn't want to exceed sidewall max at highway speeds. Strange that my rear tires have a different sidewall max....

It was all nighttime driving, and I tried to keep a low top speed of about limit-minus-5. For SL=60, that put us at a comfortable 55. But when the SL took off to 70, I tried 64 for awhile but met with marital ire. So we went 70 for some time until the family was all asleep, then we returned to more reasonable speeds. And there are some good stretches of 4 lane non-megahighway with SL=55 or 60 that made for lower speeds too. (e.g., SC38 and US501).

I used CC most of the time on I-95, but on those back roads found some DWL opportunities and went without CC (especially on isolated overpasses with pretty substantial slopes up and down).

I also had about 20 miles of distant drafting on the way down on I-95. Nothing unsafe -- at least 2.5 seconds, but I could sure feel the difference in wind.

Ok, cut to the chase, I met my goal and hit 25.8 MPG for the trip. I was a spinning banana about the whole thing. :Banane10:

I'm quite encouraged, and looking forward to taking this vehicle to 30MPG once it is "mine" during my stay-at-home-dad stint coming up.

Thanks for all the tips.

:D Good work!

Hey, 26 mpg -very good for a 4500 lb brick!

My tires-Suburban- have different sudewall pressures, but they are different types. The rears are LT -light truck -Michelins , the front are P- passenger tires of a different brand.It sure didn't come from the factory like that.

The door jam does call for very different pressures - 32 41 or so such.Maybe this is typical for body on frame SUVs with tow potential?

Great work. What would you guess your average speed was -65 mph or so?

Charlie

awesome job! 25.8, that thing is rated 25 highway.

My odyssey calls for 36 psi front, 41 rear. It's probably for weight bias and potential cargo loading.

Great work. What would you guess your average speed was -65 mph or so?

Charlie

198 miles at 3hr46min on the way down = 52.5 mph. Some local driving at the beginning and the end helped lower the avg, as did my DWL around 50 mph for about an hour in South Carolina.

awesome job! 25.8, that thing is rated 25 highway.

It is 22 mpg highway old EPA, but as we all know, those tests don't account for things like my awful 70 mph portion on I-95 near the border.

I guess the improvement is modest, and I know I could do better if I were in the car alone. I'm springboarding from this. I want 30 mpg, bad. :)

Heck, 22 mpg old EPA means 20 mpg current EPA. 6 mpg better than EPA is very, very good.

Charlie