Introduction: How to Save Petrol, Save Money and Save the World!

Petrol is getting really rediculously expensive these days and scientists say that if we don't do something to reduce carbon emissions within 5 years,permanent climatic change would have taken place.If i had my way i'd buy an electric car tomorrow but unfortunatly im still a student.

Here are some methods i use to get 50% more fuel efficiency out of my 2 litre diesel toyota.It sounds impossible to get 50 whole more percent but the internal combustion engine and the way we deliver the power to the wheels is extremely inefficient process, but it is easily achievable.

Before i started driving more efficiently i used to get about 10miles to the litre and now i get about 15 to 16miles per litre.It sounds like nothing extra but do the maths.

previous fuel consumtion at 10m/l = 200miles per 20 litres
new fuel consumption at 15m/l = 300miles per 20litres

so i get another 100miles "from nothing"!

Only about 20% of all the energy in petrol or diesel is converted to motion, the rest is wasted in heat, vibration, noise, which i think is just not good enough and thats why i think that the internal combustion engine is an old technology in need of retirement or at least semi retirement and used in hybrids.

There are 5 steps to increasing fuel effiency:

Drivers Attitude
Velocity or speed

Step 1: Resistance

Resistance on a motor vehicle is broken down into two different forms:Roling resistance and air resistance..

To reduce rolling resistance:

I always fill my tires to their maximum inflation pressure or maybe about 2 psi under,the higher the pressure the less surface area in contact with the road and therefore the less resistance therefore the less energy required to move the car along.The negative side to this is to fill the tyres with too much air,and the life of the tyre will be reduced because it will wear out in the middle of the tread so you need a good balance(usually about 2 psi under the max pressure printed on the tyre)This will probably increase overall efficiency by about 5-10 percent.

To reduce air resistance:

There isn't really much you can do to affect this one because as we all know the vehicle is a fixed shape and we cannot change it.But if say you have roof racks on the car,this can effect the resistance a surprising amount so take them off when not in use.Also a shark fin low profile type aerial is more efficient than a stalk aerial.Taking these off will increase overall efficiency by probably 5%.

Step 2: Momentum

This one takes a while to get used to,you basically have to change the whole way you drive.It basically involves using your breaks as little as possible and keeping the car moving.It also makes you a much more careful driver because you have to plan ahead.Slowing down with your gears helps amazingly, because apparently modern IC engines use NO fuel when doing this.This saves quite a bit of petrol.

Step 3: Acceleration

Most people just race off from a traffic light or from a stop without giving it much thought at all.But the slower you accelerate the less fuel you burn, whats the rush anyway, you'll probably only get to your destination a few minutes earlier and more dangerously anyway.a=(v-u)/t so if u spend a longer time climbing to a speed versus a shorter time your acceleration will be less and fuel consumption is greatly reduced.Once i discovered this i started saving petrol like you cannot believe.

Step 4: Weight

This one is pretty obvious.Take all the excess shit out your car that you don't need.less weight,less energy for the engine to have to put into the car to make it move, simple as tomato paste on bread.

Step 5: Driving Attitude

This is definatly THE most influential factor when saving fuel.The mood you're in greatly influences how you drive.Drive slower and allow more time for your journey (get up 5 minutes earlier)accelerate slower break less and use your gears to slow down you'll be amazed how much fuel you can save.

Step 6: Velocity

Velocity or speed is the final factor.

Did you know that if you double your speed, you quadruple your drag due to air resistance, yes, its go slower.I travel at a maximum of 40 mph(or the lowest speed you can go in the highest gear you have)40mph might be a bit rediculous for some but even reducing your speed 10 or 20 mph can drastically save fuel.anything over 60mph basically just wastes fuel.


tinkerist (author)2011-04-02

best thing you can do to your vehicle to save fuel: adjust the nut behind the wheel!

sharlston (author)2009-08-12

my dad uses a fuel magnet it increased his mpg my 17 mpg before it was 30 mpg now its around 40 to 50

oilsaver45 (author)2008-07-28

If you save 50% with all those tips you must have been driving like a lunatic before you used them. Normally you will save around 24%.

aku (author)2008-06-14

I am using automatic transmission car...though my car fuel consumption is significantly low,I want to reduced it further...are your tips aplicable for my car as well or it just for manual transmission cars only....

johnmccollim (author)2008-02-29

I have always took it easy on the car, like letting my foot off the gas and coasting to stop signs. Plus i own a motorcycle which really saves on alot on gas in the summer months. But doing 40 mph is quite hard living around a city trying to get home on the freeway, heck you'll get run over. Driving a hybrid car would be a better option.

ichipoodle (author)2007-07-05

Sheesh, peeps, get a friggin hybrid! It may increase smug levels, and you can't help loving the smell of your own farts, but it's worth it (if you watch south park, you'll know what i mean) but don't be gay and get a Priass, get a camry hybrid (unless you're a mpg fanatic, then buy a Prius. Yes.)

HAL 9000 (author)ichipoodle2008-01-14

Hybrids? What? I drive a 1991 Honda CR-X I got for $2000, and i get 45 mpg roughly following the steps above, better than many hybrids get. Cheap and fun to drive, too. There are lots of older cars that get great gas mileage, I actually don't know why new cars get such terrible mileage, but if you just research and look around you can find a good, reliable, affordable car for about one tenth what a new hybrid costs.

uberchoob (author)ichipoodle2007-12-06

not all of us have tens of thousands of dollars to put into a friggin hybrid! On top of that, hybrids only use the electric motor up to about 20 mph. This will only affect the initial acceleration. This does help alot, but how long do you have to drive a car like that to get enough benefit to make up for the thousands of dollar spent on a hybrid compared to the gasoline model??

ichipoodle (author)uberchoob2007-12-07

ah, touche, uberchoob. not all of us have a boatload of $$$ to spend, and i think the ev mode kicks into gasoline at 42 mph. about your bit on how long it'd take to offset the cash spent; it's kinda like a solar powered house..if you want to be cool 'n casual when you drive (driving like a normal gas car) it might take longer, but if you want to hypermile (constantly using ev mode and pissing ppl off in the process, and maybe, just maybe, getting shot for being a stick in the mud), then it will definitely be less of a wait. i hope to try hydrogen fuel cell or biodiesel cars when they come out, as i already know how to make biodiesel. and totally_screwed is right, nitrogen improves fuel efficiency because it lasts longer, and it doesn't change with the weather (shrinking when the weather is cold, expanding in heat, so it's less wear and tear on the tires AND your wallet) sorry if this was too long of a response, but i was answering your question properly and trying not to type like a drunken 4th grade rockstar. Arrivederci!

uberchoob (author)ichipoodle2007-12-07

Where do you live? Your English is interesting =)

Camster911 (author)2006-11-11

Shut up you hippies

ichipoodle (author)Camster9112007-12-07

shut up you.....uhh...................camster! yeah! take that man....and stuff....=P jk dudeo

totally_screwed (author)2007-09-15

Inflating tyres with nitrogen improves fuel efficiency.
Here are a number of tips to save money.

If you drive a manual, make sure you accelerate in the appropriate gear, not too low a gear. Gasoline engines tend to be happiest at ~2000 rpm, whereas diesels prefer lower revs, RTFM!

AirmanPower (author)2007-07-20

Underinflation does not increase traction. Tires are designed for maximum traction at an optimum tire pressure. If the tires performed better at a lower pressure that would be the pressure listed on the side of the tire.

askantik (author)2007-07-09

Can't help but wonder why you aren't using used vegetable oil if you have a diesel... You can even use 50% cleaned oil straight into the mix without a conversion kit if it's warm enough outside. Do a Google seach for "Greasecar" and check out their conversion kits. The car starts on diesel in order to warm up the vegetable oil (if it's too cold outside) then you switch to veg. oil. No pollution, smells good, and same or better performance as conventional diesel fuel has been reported. Plus the fuel is free-- most restaurants PAY to have their oil hauled off and would be highly inclined to let you have it free. It is very easy to purify the used oil at home, especially with a kit.

trebuchet03 (author)2006-10-21

"But the slower you accelerate the less fuel you burn,... "

Careful... not 100% accurate - but its easier for the masses to understand. Vehicles that have adaptive control will keep the same a/f ratio while in closed loop (where fuel trim is directly adjusted based on sensor feedback). Certain events will cause the computer to go into open loop (events such has a preset throttle %, detected sensor failure, warm up enrichment programs).

On my last car, this happened at around 80% throttle. I discovered this with a signal monitor attached to my O2 sensor. If you have the money, or know someone with a fancy OBD2 interface (if your car is OBD2 compliant) - you can find out actual numbers and get stored trends out of the box :)

I'm not sure what my current car does - it uses a wideband O2 sensor - so the 0-1v voltage comparator won't work on it :P

Something to add to resistance... Internal resistance plays a HUGE role too. Keep up with oil changes. 3K miles is a little early in my opinion (disturbs oil films too often). But keep oil at the max correct level and use a quality oil. What's a quality oil? Can't say - you'll have to do oil analysis on used oil to see how your motor handles it (this testing costs $20). Also DO NOT overfill. You'd be amazed at the viscous losses you'll have if your crank (or counterweights) is in contact with your oil.

CameronSS (author)trebuchet032007-02-14

One way to learn to drive more efficiently is to get a car that is not overpowered...The car companies want you to think that you need a 350 hp, turbo-ultra-super-dupercharged V-8 that requires 95 octane fuel to haul you to the grocery store at 35 mph. I drive an old (1980) electric truck around town, with a 20 hp GE motor. No power brakes mean that you learn to slow down earlier, and lower power means you learn that accelerating to the red light at the top of the hill doesn't always work out...On the other hand, that time I popped the clutch into first and kicked that Camaro's butt was pretty cool.

trebuchet03 (author)CameronSS2007-02-15

"Overpowered" and "lower thermal efficiency" are not synonymous terms. However, fuel economy would be related to a small vehicle with an large powertrain. This is why engine management is very important to keep that stoi. a/f ratio -- keeping in mind that it takes the same amount of energy to accelerate a given mass.

trebuchet03 (author)trebuchet032006-10-21

Oh... I also forgot to mention another thing...

LOWER RPM does not mean HIGHER fuel economy. However, LOWER LOAD is related ;)

I found that in a high gear under heavy load (say final gear at 25mph) - my fuel consumption goes up significantly (and into open loop). Your car's computer takes into consideration engine load (which is measured based on a variety of inputs including throttle %, engine speed, etc.).

Otherwise, you make very good points... weight is a big one, saves a lot while accelerating. Weight is not as big a factor once you're at momentum (that would be due to wind resistance) - but if there's a significant amount of excess weight, rolling resistance may become a significant factor ;)

Also, Mitsubishi published a technical paper on vortex generators several years ago... Apparently, they actually do reduce cD by .006 (for those that don't know, that is in the realm if significant) -- but a damn ugly in my opinion :P

I meant highest gear possible at lowest speed,within reason.My car struggles in 5th gear at 35mph and that will obviously eat petrol.At about 38mph it becomes pretty easy for it in 5th gear so i just go a minimum of 40 in 5th,i basically try not to let the car go lower that 2500rpm otherwise it struggles and not much higher than 3000rpm.Also i have been told that all toyota diesel engines apparently turn into air compressors when coasting in gear, i was skeptical of this,but when i used to coast in neutral i did burn quite a bit more diesel and also obviously its not as safe to coast down a massive hill with no gears if your breaks fail.Also tapping the breaks for short periods of time increases wear rather than pushing them hard for a long period...

Many modern petrol engines do the same fuel cutback while in gear at 0% throttle (related to my comments on load ;) ). My old car did this, and the VW community has determined my current car does the same. The drawback is emissions. Too much "cold" air will bring the catalyst below optimum (not to mention engine internals) and the computer will loose feedback from the O2 sensor if it gets too cold (some computers may kick the heater element back on). To get around this, the mfr's can allow (and probably do) a small amount of fuel to keep temperature up.

T, that was a fascinating pdf, thou not strictly applicable, I might make up a bunch of delta VG's and see what putting them along the back of the roof line of my truck does, other than make people laugh.

Yeah... not applicable in cetrain situations (trucks, hatchback with steep cutoff, etc.)... but because it actually did something at all is amazing (I was skeptical at best until I came across that).

spinach_dip (author)trebuchet032006-10-21

Diesels are different. There's no throttle on a diesel, no choke either. The air/fuel ratio is not a constant. When a diesel is at idle, it's only injecting enough fuel to overcome it's internal resistance. When it's at full load and there's more fuel than oxygen being injected, the diesel smokes. Many diesels are limited not by the amount of air and fuel they can inject, but by the thermal limit. My injection pump is detuned, and I could turn it up, but it's recommended to install a pyrometer to make sure the exaust gasses arn't getting too hot. Crank up the injection pump and go extra heavy on the stupid petal, towing something heavy up a tall hill and you might just melt the tops of your pistons. I know you are down in florida, but have you ever seen those snap on cloth things that cover a truck's radator? They use things like that on diesels because in extreme cold, there's a lot less waste heat from an idling diesel engine than a gas one. It also follows that the same engine that's detuned for a truck can produce a lot more horsepower when installed on a boat. A boat in the water has near unlimited cooling capacity.

spinach_dip (author)spinach_dip2006-10-22

[quote] There's no throttle on a diesel [/quote] err, i mean throttle plate

lemonie (author)2007-01-21

Give your car that ground-hugging, low suspension look, by putting a dozen paving slabs in the boot/trunk and a couple of bags of building sand in the footwells... A point worth making on this subject would be "use a vehicle that can do at least 35 miles to the gallon". While fuel prices have been high for years in the UK (due to heavy taxation. And european cars tend to have high fuel efficiencies because of this) it make me laugh when Americans whinge about a price-hike, like cheap gas is written into the constitution...

tomtom (author)2006-12-05

I have had a VW Golf with a diesel engine for almost three years now an I would never go back to petrol. I get about 30% better consumption than for equivalent petrol. The tip I would give is to try and get a car with a consumption monitor. This helps you to learn economic driving so much easier as you can se the immediatel effect of your driving on consumption. The VW onboard computer monitors instantaneous/average and cumulative consumption.

0.775volts (author)2006-10-23

You make some good points, Esp. your philosopy of driving (I think that is by far the most pertinent suggestion, not to mention that your car will last MUCH longer if you don't drive the hell out of it). But, a 5% Fuel efficency increase for changing your ANTENNA? come off it, man, that's crazy talk.

the african does not talk crazy (author)2006-11-14

dear african andy, if you are actually african, what if the driver is fat? does that make any difference to your theory? and if you do do 40 everywhere, do people want to beat you with a large stick for going so slow?

SurferGeek (author)2006-10-23

Cheaper to replace brake pads/rotors than it is to replace/repair your transmission!

trebuchet03 (author)SurferGeek2006-10-27

that's what I thought for a long time too... I always said "use the brakes, hey! its even got the name." But I live in S. Florida -- no hills. In areas with steep grades or long downhill runs - engine braking is necessary for safety reasons. There's a reason the skyway has signs about this (well they used to) and about letting your brakes cool.... Yes, transmission is more expensive to repair. Yes, your safety is worth more than your transmission ;)

Zaneblade (author)2006-10-22

one thing that has not been mentioned if the differences in fuel that is used when you have your clutch up/down when you are in/out of gear many people when driving put there clutch down and take the car out of gear when they are going to have to choose a gear they are about to go in but arnt sure at the time... this infact uses 2x the normal amount of petrol that would normally be used if you are in gear... also if you are in gear and have you clutch down you dont actually use any fuel... so if your going down hill its always nice to put your clutch down and coast down the hill... this has a slight effect on your clutch and will means it wear away quicker.,... but if you do it at the correct time it will save you alot more than the $50-$100 it costs to get you clutch replaced once in a blue moon

trebuchet03 (author)Zaneblade2006-10-22

when you say clutch down... do you mean out/disengaged?

1. Coasting out of gear (especially down hill) is VERY dangerous.
2. Keeping the clutch disengaged puts extra wear on the throw out bearing
3. While in gear with 0% throttle -- just about every car nowadays will cut back on fuel... Less than fuel required to idle.

Replacing a clutch and getting a clutch replaced are two very different things. If you can DIY - $50-$200 is about the cost of materials (depending on make/model, type, brand etc.). If you are getting it done... expect that to be much higher. My last car cost $400, my current car costs $700-$800 using an aftermarket OE replacement.

Tool Using Animal (author)2006-10-22

I've got an F150 (love that truck more than my wife) anyways, I've tried comparing tailgate up tailgate down tailgate off, regular driving, driving the speed limit and driving just as fast as i think i could get away with. Not one made a damned bit of difference in economy (I consider the .1mpg difference within the error range). However that said driving the speed limit did help with my stress level because it irritated other drivers SOOO VERY MUCH, ha ha. Now maintaining the engine made a huge difference, i had a leak in the vac system, replacing a cracked hose brought the milage up 2mpg

aquax (author)2006-10-21

"use your gears to slow down you'll be amazed how much fuel you can save"

Actually, all you'll be saving is your brakes.

By downshifting, and using the engine's drag to slow you down, all you're doing is increasing RPM, which increases the amount of fuel you use. Granted, your fuel injectors will be working at a minimum duty cycle already because you've got your foot off the gas, but minimum duty cycle * 1500rpm is less fuel than minimum duty cycle * 2500rpm.

Your best bet, if you have a manual transmission is to take the car out of gear (which will drop it to idle speed RPM), and coast, and apply brakes as needed.

Granted, this is a tiny bit of fuel savings, but if you do a lot of driving down hills, it could save some gasoline (err petrol).

spinach_dip (author)aquax2006-10-21

some diesel engines (in consumer cars) specificly shut off the flow of fuel and turn into air compressers on the long downhill runs. But yea, "Jake Brakes" on the large trucks are used mostly because it makes the mecanical brakes last longer.

aquax (author)2006-10-21

"The negative side to this is to fill the tyres with too much air,and the life of the tyre will be reduced because it will wear out in the middle of the tread so you need a good balance" Not to mention safety is compromised. With less tire touching the ground, braking is less effective. If you had to do a panic stop, your car would not stop as quickly as one with properly inflated tires. This could be the difference between avoiding an accident, and being in one. It's one thing to save fuel, but it's another thing to sacrifice basic safety tenants.

theRIAA (author)2006-10-21

i wish my car ran on petrol, we only have crappy american gas...

trebuchet03 (author)theRIAA2006-10-21

I really hope that was a joke... pretty funny - I just can't tell :P

Ushanka (author)2006-10-21

Hooray for physics! Stuff like this makes me happy.

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