100+ hypermiling / ecodriving tips & tactics

[PaleMelanesian]

In my case, I can drive 10 miles, 10.6 miles, or 11.3 miles. After a year of testing, they all consume the same fuel. So I take the 11.3-mile route. If the shorter one used less, I would go that way. You have to test it and make your own decisions.

[MetroMPG]

Agreed, PA32R and PaleMelanesian. The issue of route selection for minimum fuel consumption vs. max mpg is touched on in "take the road less traveled".

Have to accept also that some people treat MPG as a sport where the number is more important than the total fuel use, and vice versa. Everyone has different motivations.

[Dan.]

Found one that isn't on the list!

Always fill up at the same station - And no, it's not a numbers game. Has to do with the fuel trim tables in most cars (visible through SGIIx). When you change brands of gas it can cause your trim tables to go through a bit of re-programming. This can have a small (or large) hit on MPG. The idea is to reduce the variance in the fuel going through your engine as much as possible. Using the same brand gets you most of the way there, but filling at the same station cinches the deal. Certain metro areas (like Houston) require special blends of gas. If someone was to fill up at a shell in Bryan, TX they would get totally different gas than filling up at a shell in Houston. Sticking to the same station (and same pump if your wacky) reduces the probability of variance in your fuel mixture as much as possible, hence mitigating the reprogramming of trim tables to a minimum. As a side note I'd say that high dollar brand names are more consistent than bargain gas. One other bonus with using the same station is that you might actually get lucky and hit the same batch in two consecutive tanks. The station has huge underground tanks. If you fill on Monday and Friday (pick any two days) you might actually catch them before they get their next shipment of gas. Also when they add a batch, that change is blended throughout the whole station's reservoir, reducing the change per gallon. On the "numbers game" side, using the same pump will reduce the variance from tank to tank since each pump is calibrated independently.

I've been doing this since November and it has a HUGE impact on my Ford. Not so much on my Toyota. I'd say changing stations reduces my tank numbers by 15% no the Mercury. Takes about 3 tanks for the trim tables to settle down and ease back in to the consistent 30+ range.

If I can only give 3 tips to someone it's:
1) Tire maintenance (air, rotation, balance, align). <= On the list.
2) Drive your car like you'd ride a bike. <= On the list.
3) Always fill from the same brand, station, and pump.

Originally Posted by thebrad

I know I'm probably an exception here, but I generally fill up at the cheapest place in town (Costco) and now that prices are on the rise they are generally subject to 15 minute or more lines. Anyway, I shut off the engine and wait for all cars in front of me to fill up and then I push my car up to the spot and proceed to fill.

Nice... Try finding the station that is consistently cheapest (or in the bottom 3). Pick a pump there and commit to filling your next 5 tanks there. Make sure to try this the month AFTER they switch to the Summer gas. You should see an improvement and save money over the long haul.

Originally Posted by Doofus McFancypants

I had not thought about backing into spots. Sometimes when i get to work later than usual, the good Pull out spots are taken and i had wondered what the best alternate was. Now i know - back into a spot with a warm engine to allow pull out with a cold engine.

I've never interpreted "face-out parking" as backing into a slot if it means you need to burn gas to do it. What you do is find a slot on a hill. Then you coast (engine off) up the hill just past (10 feet) the slot. Then like a pendulum, you'll stop and start rolling back. Cut the wheel and your face-out parked on the top of a hill. Perfect. Only really makes sense if you can do it while in an engine-off coast using the kinetic energy you already have invested in your mass (car).

PS... Absolutely fantastic list Don't change a thing... Well other than my suggestion and the "printable version" thing

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[Dan.]

Opps. Found another one two, although some get pretty touchy on this one being just plain nutty.

Fill up with cold gas - Most non-gaseous liquids have very little thermal expansion. But.... petrol has more thermal expansion than say... water. It's not much, but it is some. So the theory goes, if you pump 25 gallons of gas at 6pm (when the sun has been beating on the station all day) the petrol you pump will be a few degrees hotter than if you fill at say 4am in the morning. The petrol expands when its hot so 25 gallons of cold gas may equal 25.001 gallons of hot gas. If theres a chemist out there they can give better figures. Perhaps it's 25.000g vs 25.100g. 12 oz of gas is a lot to me .

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[MetroMPG]

Originally Posted by Dan.

Always fill up at the same station - And no, it's not a numbers game. Has to do with the fuel trim tables in most cars

Thanks, Dan - I'll add it. I presume the effect could go the either way though: if you happen to switch to a fuel brand with a lower energy density (from a previous high energy density fill), you'll have "lean burn" advantage until the O2 sensor finishes adjusting the fuel trim.

I wonder about the cold gas tip though. Not questioning the physics, of course. But is it more of an economics issue than an efficiency issue? The difficulty is how do you choose to buy cold fuel vs. warm? (My reading on the lateday vs. early morning fill timing is that underground tanks are mostly unaffected by atmosperic temp fluctuations.)

I love these tips that split hairs. Their impact may be somewhere between nil and tiny, but the fact that people are interested enough to consider them is very, very cool!

They're also the kinds of tips that cause those who are anti-hypermiling inclined to yell and pull out their hair.

[Dan.]

Originally Posted by MetroMPG

Thanks, Dan - I'll add it.

Very Cool. The digg count is going through the roof on your tip list. My google alerts on hypermiling is getting hyper too. Great job!

Originally Posted by MetroMPG

I wonder about the cold gas tip though. Not questioning the physics, of course. But is it more of an economics issue than an efficiency issue? The difficulty is how do you choose to buy cold fuel vs. warm? (My reading on the late day vs. early morning fill timing is that underground tanks are mostly unaffected by atmospheric temp fluctuations.)

Your right on target. The "tip" doesn't reduce your tail pipe emissions, but it does reduce the amount of money you spend on gas each month. Think of it as cold gas costing less than warm gas. The tip can be summarized into Always fill up in the morning, never in the afternoon. Now as far as "what is the temp delta in an underground tank", depends. In Houston, the tanks aren't really underground, but rather in-ground. Think of a back yard swimming pool with a tarp over it. That tarp is made of concrete and has pumps on it. Drill 6 inches through the concrete and your in the stations storage tank. So yes, sun hitting the concrete all day will heat the "roof" of the stations storage tanks, and through convection, the gas itself.

The brainchild of this tip was a law passed in Canada (I believe) a while ago. Basically gas trucks were getting short changed in the winter. They'd fill their trucks to make their deliveries. They would fill 9000 gallons at the distribution center, but only sell 8950 gallons returning the truck bone dry. What was happening was that the gas would cool during the deliveries. So the solution was that tankers sell by the pound. Consumers buy by the gallon. Doesn't matter if the gas in a 9000 gallon (sealed) tanker is warm or cold. It's weight never changes. The fact that the tanker drivers had to push this law through got us thinking that it must be a big enough volume change to warrant all that effort.

Here's a source (the state of Utah): http://geology.utah.gov/sep/energy_e...leage_tips.htm

Google keyword list {gas density morning}: http://www.google.com/search?q=gas%20density%20morning

Here's a counter-source that claims that all US pumps use temperature compensating volumetric flow meters.
I can't confirm this claim: http://www.omega.com/techref/flowmetertutorial.html

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[guitarterry]

the point of orbit is the highest mpg, not the least fuel used. or in laymens terms. cuting off your nose to spite your face.

[Dan.]

Originally Posted by guitarterry

the point of orbit is the highest mpg, not the least fuel used. or in laymens terms. cuting off your nose to spite your face.

Orbit can be used productively. One example would be timing your exit so your lane is clear. Without the orbit, you have to take a hard stop killing (and regaining) all your velocity. With a well timed orbit you can exit the parking lot with about 50% of the velocity you started your orbit with. I've done this (maybe twice) in the last year or so. Nice to have in the grab bag for the one time in a blue moon that you could use it.

DISCLAIMER: The obvious stuff about not orbiting in a crowded parking lot and not around people trying to cross all applies of course. People come first... MPG comes 42nd.

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[guitarterry]

I was talking about not parking till your done coasting, even if the spot you want is open. then maybe even coming back around and parking in that same spot. I cant even figure out what timing your exit is talking about. Sounds like your talking about leaving the parking lot, not parking. It does sound good though. Make sure your lane is empty before you exit your parking spot.

[ihatejoefitz]

I really enjoyed the list! Awesome job. Especially 12.

12) Leave early and don't rush

The enemy of efficient driving is finding yourself in a rush. Leave for your destination a little early so you don't feel pressure to drive faster, brake later and otherwise fall back into bad habits.

Driving efficiently can be much more relaxing than the typical person's driving style, but you need to allow a bit of extra time.

Ideas for consideration...

-Use lighter weight oil.
-Make aerodynamic modifications. You touched on this with the roof rack removal tip, but there are lots of easy and effective mods.

Also, I feel like #14 needs some qualification. I haven't tested, but my guess would be that IRL the cons would outweigh the pros.

14) The 'corridor effect'

All else being equal, traveling at a constant speed on a freeway within a flow of traffic (in the same direction) is more efficient than going the same speed in isolation. The reason is aerodynamic: a flow of traffic generates a localized wind current in the direction of travel. You will benefit from this artificial breeze.