hypermiling update: now 41.5mpg in my 2001 sentra (epa says 21 city / 27 hwy / 23 combined)

i just had my 3rd fill-up after starting hypermiling. i'm getting better at it!
i've increased my revs slightly after reading that most engines don't lose effeciency until they get up to about 3500 rpms. so i now let it get up to 2500-3000 before shifting up. this gives me a bit more acceleration, apparently at no cost.

i have also started pulse & gliding on the highways, traffic permitting. i keep a close eye on the rear-view mirror for anyone approaching fast, but rather than keep it set at 57 or so, if all is clear, i'll pulse up to just under 60 and coast down to 55, or even 50 if there's no traffic at all. this is the main thing i've done differently, so i think that's what's responsible for the extra 4 mpg.

i will say this: while i've always been fond of stick shifts, i very much doubt i'd ever want to get an automatic transmission. you get so much control with a manual, most of these hypermiling tricks can't be done easily with an automatic (although the hybrids build some of this stuff in).

my earlier post after my first effort at hypermiling:

http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=389x3583558



on edit:

i rechecked the epa estimates and they now list the 2001 sentra as 23 city/30 highway/26 combined. this is not because the sentra got better, but because they changed their formula and they wanted to make this comparable to the way they calculate mpg for the 2008 models.

in any event, 41.5mpg still clobbers their numbers!

I just got 38.5 in my 99 Civic.

It's an automatic.

Just paying attention really helps. When you drive consciously, you realize how many bad drivers there really are.

Good luck.

and then floor it when the coast is clear.

i used to think about the immaturity, or the safety factor. now i just think about how much gas they're sucking down!

the expression "they don't want to be late for their own funeral" often comes to mind....

During my 12 mile commute to work, I drive through 6 miles of suburban stoplights and stopsigns, and then through another 6 miles of mostly highway driving (55 mph).

I have on many, many occasions found that those who drive in the previously mentioned manner (jackrabbiting, flooring it and then hitting the brakes) are at best 10-20 seconds ahead of me when they drive the same route I do. Many times, I just pull up to them at a red light 10 seconds after they do, after they pass me a few miles back.

they had two sets of cars. both cars had to travel some 30 miles in a mix of highway and city driving.

one set observed ALL traffic laws and safety practices. driving the exact speed limit, full stop at stop signs, carefully signalled lane changes, etc., as well as gradual acceleration and so on.

the second set threw caution to the wind and was free to basically do whatever it took to get there fastest.

each set had observers in the car to record how they observed the laws.


on average, the law-breaking set of cars racked up OVER 100 traffic and safety violations EACH. and they got there 2-3 minutes ahead of the other set. not remotely worth it.

And I don't speed.

to hypermiling. It appears this page is relevant: http://www.hypermiling.com/

Edit: And these:
http://www.hypermiler.co.uk/
http://en.wikipedia.org/wiki/Hypermiling

I'm not into the finer points of hypermilling...and trying it in rush hour Chicago traffic isn't ideal for much more than trying to stay alive...but on the open road when I can "stretch things out", I got 35MPG on a recent road trip. I try to keep the revs on my 5-speed between 1,500 and 2,000...that seems to be the ideal rate.

CNN had a report about hypermilling...this dude was doing it in Midtown Manhattan...he has a lot more cajones than I do.

Congrats on your mileage...it's a shame American cars can't deliver this type of performance.

Just to let ya know.

:rofl:

Carly

actually there is a bit of debate that driving "slowly" (i.e., the actual speed limit) might INCREASE overall gas consumption. the car driving slowly obviously saves, but if enough cars slow down behind and rev up to pass, they may spend all your savings and more. not a problem from a personal pocketbook perspective, but it is a problem from the global oil dependency and carbon footprint perspective.

I drive a late-model Toyota Camry with 4-speed automatic transmission. Like most automatics these days, it has a button on the shifter for "overdrive".

With the "overdrive button" depressed, the car normally changes gears at a slightly lower RPM. However (in my Camry), the only way to achieve 4th gear for highway driving is to activate overdrive. Otherwise, the engine will top out at 3rd gear making speeds over 50mph a real stresser for the motor.

In normal about-town driving, I leave the overdrive switch off, turning it on only when I travel above 45mph for any extended distance. By my estimate, leaving "overdrive" off by default increases my milage by between 2-4mpg. Many drivers with automatic transmission are unaware of this and often just leave their car in "overdrive" all the time.

If you are careful, you *can* shift manually with an automatic transmission, taking off from stops in 1st gear, shifting up into second around 2500rpm, and "D" (Drive) once you've stopped accelerating. Just be careful not to accidentally shift into "R" or "P" while you are still moving. Great way to ruin a good engine. :)

tiptronic or something like that. it's an automatic transmission, but you can override it and use it like a manual if you prefer.
unfortunately, i don't drive the mercedes very often, and the shifter is laid out like an automatic, so manual shifting is not at all natural for me in that car. worse, neutral is not very easy to get in and out of.

with practice, though, i could do some of this stuff in that car as well.

Or should one wait for a complete stop before pressing it? Thanks.

I was just reading an online how-to about pulse-and-glide techniques, and it said to shift to neutral after you pulse up to a higher speed so that you can glide further.

I have an automatic transmission Scion xA that I've been mildly hypermiling with good results. Do you know if it is safe (from a mechanical stand-point) to shift an automatic transmission car into neutral while driving at highway speeds, then shift back into drive when you need to pulse again?

Keep up the good work, BTW!!!

To answer your question, "No", do NOT shift into neutral between "pulses" when driving an automatic. Simply take your foot off the gas.

Besides the obvious danger of shifting into Reverse (just above Neutral on an automatic shifter) while you are moving, shifting into neutral also untensions the timing belt, and shifting back into gear snaps it tight again. Repeatedly snapping the timing belt tight is the surest way to get it to break as quickly as possible (I learned this the hard way). If the timing belt breaks, the engine goes dead and you will find yourself coasting to the shoulder (praying you make it in time before your car rolls to a grinding halt in the middle of the freeway) waiting for a tow-truck to ferry you home.

in my manual, i take the foot off the gas and depress the clutch pedal and i'm quietly coasting. i usually keep it that way (as opposed to putting the shifter in neutral and releasing the clutch pedal) because it's fewer steps in case i need to re-engage the gears in a hurry. that said, it's harder on the legs :)

if you just lightly let up on the gas pedal at the same time as you nudge the shifter towards neutral it will slide right out of gear with not problems and no wear on anything and if you lightly press on the gas pedal as you are nudging the lever towards the gear you want when the engine and the drivetrain sycronize to one another same thing it goes right in gear with no wear on anything or stressing anything out. Just in case you might care to know that. Clutches and throwout bearing are expensive to buy and replace and if you're not using them they are not wearing out.:-)


add: you can get so smooth with this operation that a passenger will not even know you had done either, out of gear or back in gear, short of watching you do it that is.

It always seemed to me that a laboring engine isn't very efficient, especially when going up steep hills.

Are you shifting at 3000 rpm at every gear?

if the engine is lugging, that's very bad; if the revs are too high, that's also bad (and breaks down your oil, to boot). in between is just right. the exact range varies from model to model.

going up hills i do choose a lower gear to keep it from lugging.

on level roads, i am upshifting at 2500-3000 at every gear. i'm not sure if i should be doing it differently for different gears.

I'd never ever buy an automatic, I'm happiest when flying along in neutral!

to 39 psi. The tire runs cooler than with normal air plus the tire dealer has said
I've had no wear. Coasting lasts longer too.

I keep my rmps under 3000 at all time. I'm getting 34 in my Subaru now.

It doesn't cost anything either. I've had these tires and its the first time that
I've never had to put air in them, not one leak. Normal air causes the stem to leak and deteriorate also
the tire itself. Ask a tire dealer and what it would cost where you live. Automotive Racing
uses this air exclusively.

i'm in connecticut, and the only places listed in the area by http://www.getnitrogen.org/ is costco.
i'm not a member (we prefer bj's) and in any event it says they'll only do it if you bought your tires there.

pure nitrogen has not been shown to make any difference at all to mileage. Simply keeping them properly inflated with regular air (that you can get for about 50 cents, less if you have your own air compressor vs. $30 for "nitrogen").

I don't pay $30 and you made that up too
Why don you research before you make ignorant statements?

Canadian Study:

Situation
1. Canada's Drexan Corp runs 70 tractors and 117 trailers in longhaul operations
2. Conducted 9-month double-blind study testing effectiveness of nitrogen tire inflation program
3. Results published in paper prepared for annual Clemson University Tire Industry Conference

Significant Points
1. Nitrogen system improved fuel efficiency by 3.1% compared to tire pressure maintenance program using air
2. Improved 6.1% compared to no tire pressure maintenance program
3. Study also uncovered 86% gains in tire tread life
4. Reduction in greenhouse gas emissions could be exchanged for revenue on carbon trading markets

Background
1. Nitrogen permeates through tire casings more slowly than ambient air
2. Nitrogen-filled tires maintain optimum pressure longer
3. Dryer nitrogen helps preserve tire rubber and protect casings from corrosion damage

http://www.automotivedigest.com/view_art.asp?articlesID=23122


Plus more stuff

http://www.getnitrogen.org/why/index.php
http://www.automotivedigest.com/view_art.asp?articlesID=23122
http://www.getnitrogen.org/pdf/print_articles/Pitts%20Post%20Nitrogen%20article%2011%201%202004.pdf
http://www.getnitrogen.org/pdf/print_articles/Tire%20Business%20-%20N2%20Inflation%20Good%20Move.pdf
http://www.getnitrogen.org/pdf/print_articles/MTD%20August%202005%20Nitrogen%20article.pdf

Air is 78% nitrogen already. Or, is it the lack of oxygen? It must be the latter, maybe it keeps the rubber from oxidizing?

Here, the only place I've seen charge twelve bucks. And how do they purge the air to make it (nearly) pure oxygen?

Lotta questions. I'll stop now. Just curious, because I've heard about this nitrogen thing before.

My tires are 36 psi on plain air.

Even with the old numbers, I had no problems beating them, and I dont drive like I have an egg under my foot either! I personally think the old EPA ratings are more accurate.

This is something that really helps decrease rolling resistance and improve MPG, despite the incessant giggling from McCain's little Flying Monkey Brigade (Limbaugh, Hannity, etc.)!

I'm getting over 38 mpg overall in my '02 Honda Accord - just a basic 4-cylinder engine with a 5-speed transmission, after boosting the PSI along with gentle acceleration, gliding in neutral, limiting my interstate cruising speed to 65 mph, shifting at no more than 2250 rpm, and some other very minor things.

i know i can go higher, but i've heard there are safety issues.
i suspect they are overblown, but i haven't researched it enough to actually do it yet.

Driving much like you described...

Keeping the tires inflated too...
I believe some models of the 2001 Sentra and the G20 might have the same engine...

SRD20E or something like that...

I put four gallons in at a time and keep RPMs below 2.5k during acceleration.

My daily commute is mostly 40 mph city. With few lights. in 5th 2 40 mph RPM is below 2k.

longs costing up to red lights and I try to keep moving all the time.