Saving on Petrol Usage

eddiem74

Got this via email (kind of a chain email), is it truth or myth, most ideas seem to make sense and some are obvious really.

I don't know what you guys are paying for gasoline.... but here in California we are paying up to $3.75 to $4.10 per gallon.(UK price in March 2011 is over £6.00 gallon or about $10.00!!!!!!) My line of work is in petroleum for about 31 years now, so here are some tricks to get more of your money's worth for every gallon: Here at the Kinder Morgan Pipeline where I work in San Jose , CA we deliver about 4 million gallons in a 24-hour period thru the pipeline. One day is diesel the next day is jet fuel, and gasoline, regular and premium grades. We have 34-storage tanks here with a total capacity of 16,800,000 gallons.

• Only buy or fill up your car or truck in the early morning when the ground temperature is still cold. Remember that all service stations have their storage tanks buried below ground. The colder the ground the more dense the gasoline, when it gets warmer gasoline expands, so buying in the afternoon or in the evening....your gallon is not exactly a gallon. In the petroleum business, the specific gravity and the temperature of the gasoline, diesel and jet fuel, ethanol and other petroleum products plays an important role. A 1-degree rise in temperature is a big deal for this business. But the service stations do not have temperature compensation at the pumps.
• When you're filling up do not squeeze the trigger of the nozzle to a fast mode If you look you will see that the trigger has three (3) stages: low, middle, and high. You should be pumping on low mode, thereby minimizing the vapors that are created while you are pumping. All hoses at the pump have a vapor return. If you are pumping on the fast rate, some of the liquid that goes to your tank becomes vapor. Those vapors are being sucked up and back into the underground storage tank so you're getting less worth for your money.
• One of the most important tips is to fill up when your gas tank is HALF FULL. The reason for this is the more gas you have in your tank the less air occupying its empty space. Gasoline evaporates faster than you can imagine. Gasoline storage tanks have an internal floating roof. This roof serves as zero clearance between the gas and the atmosphere, so it minimizes the evaporation. Unlike service stations, here where I work, every truck that we load is temperature compensated so that every gallon is actually the exact amount.
• Another reminder, if there is a gasoline truck pumping into the storage tanks when you stop to buy gas, DO NOT fill up; most likely the gasoline is being stirred up as the gas is being delivered, and you might pick up some of the dirt that normally settles on the bottom.

Anan1

I'm no expert, but my common sense is telling me that the first three are nonsense anyway.

robertxxx

For the first one this is taken into account by the pump, heard guy on AA talking about that.

shedweller

Total myth.

Maintain your car properly, dont accelerate so hard, don't get up to silly speeds and you'll save fuel.
Drive intelligently up to red traffic lights, which means lifting off the throttle and engine braking (not that thing trucks do!) in whatever gear you are in. Time it so you come to a stop at the lights. Zero fuel used while engine braking. If thats your thing.
If you're flush with cash then keep the boot down!:D

fasttalkerchat

First 3 are negligible for normal amounts of fuel. Last one is possible if the fuel isn't filtered before it goes through the hose.

cruizer101

1. Pretty sure pumps here compensate for temperature

2. & 3

Did some quick calculations to see how much you could potentisally lose.
While since did chemistry but think I'm right.

Technical bit
Lets say you have an 80l fuel tank full of vapor, if we treat it as an ideal gas, 22.4l of gas per mole, thats goint to be about 4 moles of petrol. 4 moles of petrol is about 600ml(liquid). (molar mass 0.114kg/mol, density 0.714kg/l gives 150ml/mol)

So if you have a fuel tank full of petrol vapor as it will be when empty and all that gets displaced to outside the tank as you fill up, there is potentially half a litre of petrol there. Which is more than I thought anyway.

dr.fuzzenstein

Just make sure your tires are up to or over recommended pressure, I keep mine at 35 psi.
Underinflation could cost you up to 5% more fuel usage per psi!

pajo1981

The bit about colder liquid being denser is bollocks anyway- just ask any junior cert science student. FFS.

shedweller

dr.fuzzenstein wrote: »

Just make sure your tires are up to or over recommended pressure, I keep mine at 35 psi.
Underinflation could cost you up to 5% more fuel usage per psi!

Just be aware that people will say grip is compromised. They won't provide facts and figures, just scaremongering.
On balance though, the fuel saving is small from going above the recommended pressure. Whats really saved here is not replacing tyres as often. And given the cost of tyres these days, thats not bad.
Also, higher pressures will show up worn shocks earlier, due to the tyre transferring a little more movement to the shock absorber.

I suppose the low recommended pressure allows for all sorts of numptys on the road. But if you know what you are doing then you'll be fine.

dr.fuzzenstein

shedweller wrote: »

Just be aware that people will say grip is compromised. They won't provide facts and figures, just scaremongering.
On balance though, the fuel saving is small from going above the recommended pressure. Whats really saved here is not replacing tyres as often. And given the cost of tyres these days, thats not bad.
Also, higher pressures will show up worn shocks earlier, due to the tyre transferring a little more movement to the shock absorber.

I suppose the low recommended pressure allows for all sorts of numptys on the road. But if you know what you are doing then you'll be fine.

+1
Been driving at higher pressure for since I can remember, never had a problem, I also hate that "spongy" feeling of underinflated tires.

Blazer

shedweller wrote: »

Just be aware that people will say grip is compromised. They won't provide facts and figures, just scaremongering.
On balance though, the fuel saving is small from going above the recommended pressure. Whats really saved here is not replacing tyres as often. And given the cost of tyres these days, thats not bad.
Also, higher pressures will show up worn shocks earlier, due to the tyre transferring a little more movement to the shock absorber.

I suppose the low recommended pressure allows for all sorts of numptys on the road. But if you know what you are doing then you'll be fine.

so pray tell...share your scientific knowledge and facts to prove it..

shedweller

so pray tell...share your scientific knowledge and facts to prove it..

I'm no scientist and don't have the resources to properly and scientifically test it. But i did test it anyway. Stops very well in wet and dry. Even a sceptic co-carpooler was surprised by how good the stopping force was. So, thats good enough for me.

Now you have to prove me wrong, with numbers, to show me how wrong i am!

Go on, i dare you!

C4Kid

Regarding Point 1 :

I've heard that from numerous sources so there may perhaps be some truth to it. Theres a station near me that has a "@ 15 degrees" sticker next to the quantity in litres screen. Probably indicating that the quantity readout may not be exact and vary slightly depending on temp.

pajo1981

C4Kid wrote: »

Regarding Point 1 :

I've heard that from numerous sources so there may perhaps be some truth to it. Theres a station near me that has a "@ 15 degrees" sticker next to the quantity in litres screen. Probably indicating that the quantity readout may not be exact and vary slightly depending on temp.

'tis parts in a 1000. But I suppose on a big temp swing it could be 10 or so cent on a fill.

questionquick

shedweller wrote: »

Just be aware that people will say grip is compromised.

Whats really saved here is not replacing tyres as often.

Also, higher pressures will show up worn shocks earlier, due to the tyre transferring a little more movement to the shock absorber.

Just to make sure i get what your saying?

So if you have pressure a bit higher tyres will last longer.... and they will inform you that you need new shocks earlier than they normally would?

And people say you get less grip if you choose a higher pressure??

Never knew any of this.

Are you supposed to go by the recommended psi on the tyre or the manual for the vehicle?

T-Maxx

Now this is some funny sh!t.

dr.fuzzenstein

questionquick wrote: »

Just to make sure i get what your saying?

So if you have pressure a bit higher tyres will last longer.... and they will inform you that you need new shocks earlier than they normally would?

And people say you get less grip if you choose a higher pressure??

Never knew any of this.

Are you supposed to go by the recommended psi on the tyre or the manual for the vehicle?

My guesses (just to jump in here):
Last longer: higher pressure means less give in the tire, less deformation of same, lower temperature, possibly contribute to longer life. Just a guess, may be bollocks.
Need more shocks: Higher pressure, less give in tire, more force transmitted to shocks, shocks have to work harder.
Less grip: Higher pressure, less surface of the tire in contact of the road, offroaders sometimes let tires down to increase the surface in contact with the road to increase grip.
This could all be marginal stuff, i.e. it won't affect any of the above to any great degree, but sounds fairly logical to me.
Can't be arsed looking it up at the moment, but that's pretty much the info I have heard over the years.

shedweller

questionquick wrote: »

Just to make sure i get what your saying?

So if you have pressure a bit higher tyres will last longer.... and they will inform you that you need new shocks earlier than they normally would?

Yes, your tyres will last longer. No, they won't inform you about premature shock wear. Do harder tyres cause premature shock wear? Maybe. Cost/Benefit? Who knows!

questionquick wrote: »

And people say you get less grip if you choose a higher pressure??

Yes, they do. Do they back it up with anything other than ridicule? No.

questionquick wrote: »

Never knew any of this.

Are you supposed to go by the recommended psi on the tyre or the manual for the vehicle?

On the manual for the vehicle.
For what it's worth, my last car retired with 100,000km on a set of tyres that i put on it. They went to the scrapyard with 4mm even tread depth on them. They spent their life at 44 psi. and i had no ill effects. No shock absorbers failed either.
But i doubt any of that will wash here. I also doubt anyone will show me how grip varies with tyre pressure.

shedweller

T-Maxx wrote: »

Now this is some funny sh!t.

Why's that?

kirving

Grip does vary with pressure. Even on a bicycle, when my tires are pumped fully, the bike will skid faster in the rain. I pump up the tyres slightly in the summer because I don't need the little bit extra grip, and prefer the easier cycle.

http://www.eng-tips.com/viewthread.cfm?qid=102250

Interesting read. Kind of related. 44 psi would be about 1.5 times the recommended pressure, not a good idea really. Ever had a blowout? The savings would be marginal, and I'd expect there'd be more centre wear on the tyre? Pressure acts normal to the surface wall, so the middle will be pushed out more. Depends on the tyre I suppose though. Very noticable on a bicycle, but I like the two ends of the spectrum.


On point one, many of the most simple instruments I've used in college have temperature compensation. It's really not a big deal to incorporate it on a petrol pump which already has very precise and accurate gauges, which in turn are calibrated frequently enough.

dr.fuzzenstein

shedweller wrote: »

. I also doubt anyone will show me how grip varies with tyre pressure.

I found some things, mostly related to off-roading and racing:

http://www.4x4tirereview.com/airdown.html

http://www.btinternet.com/~ricardo.nunnini/TirePressure.html

http://www.autocross.us/forums/lofiversion/index.php?t46.html

I don't think grip will be hugely affected in normal road use, I certainly never had any issues with 35psi, over 40 might be overkill.
It's all to do with the size of your contact patch with the road, which will be bigger with lower pressure.

shedweller

Kevin Irving wrote: »

Grip does vary with pressure. Even on a bicycle, when my tires are pumped fully, the bike will skid faster in the rain. I pump up the tyres slightly in the summer because I don't need the little bit extra grip, and prefer the easier cycle.

http://www.eng-tips.com/viewthread.cfm?qid=102250

Interesting read. Kind of related. 44 psi would be about 1.5 times the recommended pressure, not a good idea really. Ever had a blowout? The savings would be marginal, and I'd expect there'd be more centre wear on the tyre? Pressure acts normal to the surface wall, so the middle will be pushed out more. Depends on the tyre I suppose though. Very noticable on a bicycle, but I like the two ends of the spectrum.


On point one, many of the most simple instruments I've used in college have temperature compensation. It's really not a big deal to incorporate it on a petrol pump which already has very precise and accurate gauges, which in turn are calibrated frequently enough.

No, I've never had a blowout.
They are caused by underinflation. The sidewalls flex too much and wear out prematurely.
Your bike analogy is interesting, but i don't see the same with car tyres.
Your link also refers to racing tyres, which use a "sticky" compound. In this case, more footprint=more grip.
Normal road tyres dont "adhere":) to the same rules afaik.

Look, i'm not trying to change the world here or anything.
Just giving my 2 cent and from my experience, i have had no ill effects from elevated tyre pressures.

full_irish

When you're next driving... take a sharp left into closest tree/wall/polar bear etc...

"SIMPLES" (in alexander the meerkat voice)

savagecabbages

shedweller wrote: »

I also doubt anyone will show me how grip varies with tyre pressure.

How about you prove that it doesn't?
Other than a 'for what its worth' anecdote...

I could give you 10 anecdotes about higher than recommended pressure being dangerous...

shedweller

savagecabbages wrote: »

shedweller wrote: »

I also doubt anyone will show me how grip varies with tyre pressure.

How about you prove that it doesn't?
Other than a 'for what its worth' anecdote...

I could give you 10 anecdotes about higher than recommended pressure being dangerous...

Well, this could go round in circles! Apart from me actually driving on 40 psi tyres for the past number of years, there is an NHTSA report on this very subject. I haven't got it to hand at this time but it did show how grip varied with pressure. But not the way you'd think.
Anyway, we'll have to agree to disagree on this. I've seen this argument rage for a long time without any resolution. All i can add to it is that i can brake as hard as i like in the dry without the abs going and only slightly going in the wet. I can take corners as hard as i dare without sliding. Seems to me that grip doesn't drop off at elevated pressures.

maidhc

shedweller wrote: »

Just be aware that people will say grip is compromised. They won't provide facts and figures, just scaremongering.
On balance though, the fuel saving is small from going above the recommended pressure. Whats really saved here is not replacing tyres as often. And given the cost of tyres these days, thats not bad.
Also, higher pressures will show up worn shocks earlier, due to the tyre transferring a little more movement to the shock absorber.

I suppose the low recommended pressure allows for all sorts of numptys on the road. But if you know what you are doing then you'll be fine.

Nonsense. I once pumped up the tyres on my Capri to about 40psi and it was almost undrivable. Now the Capri wouldn't be famous for its finely balanced chassis and has a natural instinct to go backwards into a ditch, but it does go to show. It was scarily giddy with higher pressures though.

A bit extra in a modern car probably is no harm, I used to put 38psi in the front tyres of my focus diesel and never noticed any side effects, but it was a heavy old engine.

shedweller

For all the data that can be found, there's precious little on this subject. It could be said that "it should be obvious" etc. but there is plenty of stating the obvious elsewhere, why should grip vs tyre pressure be any different?

Anyway, i don't expect any answers or data on this. I've seen this same argument on a scientific forum where practically anything could be calculated to the nth degree, with graphs and tables to back it up. But on the subject of grip vs tyre pressure there was only insults and childish rants!!

I'll continue doing what i do and you continue doing what you do.

dudara

The biggest influencers in my car are by far and away the following

(a) air-conditioning - turn it off if not required
(b) Smooth steady driving - don't accelerate harshly or have erratic speeds. Use cruise control where possible.

Never mind vapours escaping a tank or pump. Most of the factors that control petrol consumption are linked to how heavy your foot is.

alias no.9

dudara wrote: »

The biggest influencers in my car are by far and away the following

(a) air-conditioning - turn it off if not required
(b) Smooth steady driving - don't accelerate harshly or have erratic speeds. Use cruise control where possible.

Never mind vapours escaping a tank or pump. Most of the factors that control petrol consumption are linked to how heavy your foot is.

Bigger than that are unnecessary journeys and peak time journeys that could just as easily be taken off peak.

dr.fuzzenstein

shedweller wrote: »

For all the data that can be found, there's precious little on this subject. It could be said that "it should be obvious" etc. but there is plenty of stating the obvious elsewhere, why should grip vs tyre pressure be any different?

Anyway, i don't expect any answers or data on this. I've seen this same argument on a scientific forum where practically anything could be calculated to the nth degree, with graphs and tables to back it up. But on the subject of grip vs tyre pressure there was only insults and childish rants!!

I'll continue doing what i do and you continue doing what you do.

Not arguing with what you're doing.
What is being said is that higher tire pressure=smaller contact patch.
Smaller contact patch=less grip.
Now, the difference might be minuscule, maybe not even noticeable.
How do I prove that smaller contact patch=less grip?
If you refuse to believe that is the case, then go an fit 155 tires on your car, since by your logic they will provide the same amount of grip as 205 tires.
Since you have ignored all my posts on the matter, I don't know why I bother even posting this.

dr.fuzzenstein

alias no.9 wrote: »

Bigger than that are unnecessary journeys and peak time journeys that could just as easily be taken off peak.

Makes sense, but bit of a non starter when commuting daily.

Other tips:
Take off any roof rack
Don't drive anything around that doesn't need to be in the car
Tire pressure (again)
Have it serviced on the button
Clean air filter
Aircon (Not sure, never seems to make much difference to mine)
Keep windows closed enroute
If you drive carefully, you can achieve better MPG if NOT using cruise control
If diesel, DON'T buy chaep, sh*tty diesel at "bargain" cowboy garage.
On motorways, keep constant speed and slow down by 10 km/h, you will see a difference between 120 and 110 km/h.
Remove any aftermarket spoilers, they are meant to create downforce and therefore induce drag.
Make sure cars bodywork is in order and no panels are loose, sticking out.

alias no.9

dr.fuzzenstein wrote: »

Makes sense, but bit of a non starter when commuting daily.

You'd be surprised at how many people get back into the car after they get home from work to go to the supermarket, off-licence, gym or other such journies when they could have stopped on their way home. Might only be a short journey but if the engine has cooled down, it'll be a pig on fuel.

dr.fuzzenstein

alias no.9 wrote: »

You'd be surprised at how many people get back into the car after they get home from work to go to the supermarket, off-licence, gym or other such journies when they could have stopped on their way home. Might only be a short journey but if the engine has cooled down, it'll be a pig on fuel.

+1!
I do all my shopping enroute back from work and avoid all uneccesary journeys.

NinjaK

Does braking use much petrol? Would engine breaking use less petrol?

Discodog

The right driving technique can make a huge difference. I remember watching a program where one driver achieved way better economy just by moderating their technique. The key to it is anticipation.

Advanced driving teaches people to focus their sight much further ahead that with a typical driver. So if you see a hill coming up you gradually accelerate before the hill so that you carry more momentum. On downhills you take your foot off the throttle. You keep in the highest gear without straining the engine & change gear asap. The best guide was to imagine that you had a raw egg between your foot & the throttle pedal.

Another factor is minimising breaking. Again look well ahead & try to synchronise your speed to avoid having to slow down & then use fuel building up speed again.

If you practise the technique it doesn't affect your journey times. Your average speed stays the same but you avoid the acceleration/brake cycle.

C.D.

NinjaK wrote: »

Does braking use much petrol? Would engine breaking use less petrol?

When you brake you're turning kinetic energy (read: burnt petrol) into heat. It's basically wasting petrol, better to reducing braking as much as possible by reading the road.

shedweller

NinjaK wrote: »

Does braking use much petrol? Would engine breaking use less petrol?

The engine uses ZERO petrol!!

C.D. wrote: »

When you brake you're turning kinetic energy (read: burnt petrol) into heat. It's basically wasting petrol, better to reducing braking as much as possible by reading the road.

Correct. Lifting off the throttle results in the ecu telling the injectors to stop firing.
Think of it like you were pedalling a bike. Would you redline it up to a red light? Would you gun it only to jump on the brakes in the next few seconds? But thats how loads of lads drive. Numpties!:pac:

shedweller

dr.fuzzenstein wrote: »

I found some things, mostly related to off-roading and racing:

http://www.4x4tirereview.com/airdown.html

http://www.btinternet.com/~ricardo.nunnini/TirePressure.html

http://www.autocross.us/forums/lofiversion/index.php?t46.html

I don't think grip will be hugely affected in normal road use, I certainly never had any issues with 35psi, over 40 might be overkill.
It's all to do with the size of your contact patch with the road, which will be bigger with lower pressure.

Sorry Dr. fuzz, didn't ignore you. Busy day.

Those links you provided are informative, but they either refer to off road tyres or racing tyres, both of which subscribe to different rules.
In the case of off road tyres, it really is a case of more contact patch= more grip. This being because the ground surface is so soft and crumbly that it is more a case of getting "teeth" into the ground than tyre compound. Thus: more tread=more grip.

Racing tyres become sticky when up to temp. It's this stickiness that provides grip. Thus: more contact patch= more grip.

Road tyres are different. They don't become sticky and they don't "claw" into the ground like off road tyres do.

Look, all i can say is that if i go down the road and absoloutely and completely lash the brake pedal out of it, i will stop. And without ABS.
In the wet, i will experience only a little ABS.

Make of that what you will.

Jambo221

Back when I had a car, I used to keep my spare tire and tools in a mate's garage and vice versa. Had a can of that puncture repair foam on hand and if necessary I could just call my mate and have him bring the spare. Not having the extra weight in the car made a noticeable difference.

Also kept a foot pump in the car, every so often I'd top up the air to keep things running smooth, very handy.

Jimmy Garlic

pajo1981 wrote: »

The bit about colder liquid being denser is bollocks anyway- just ask any junior cert science student. FFS.

Did you ever store vodka in a freezer?. When you pour it it is noticeably denser.

dr.fuzzenstein

shedweller wrote: »

Sorry Dr. fuzz, didn't ignore you. Busy day.

Those links you provided are informative, but they either refer to off road tyres or racing tyres, both of which subscribe to different rules.
In the case of off road tyres, it really is a case of more contact patch= more grip. This being because the ground surface is so soft and crumbly that it is more a case of getting "teeth" into the ground than tyre compound. Thus: more tread=more grip.

Racing tyres become sticky when up to temp. It's this stickiness that provides grip. Thus: more contact patch= more grip.

Road tyres are different. They don't become sticky and they don't "claw" into the ground like off road tyres do.

Look, all i can say is that if i go down the road and absoloutely and completely lash the brake pedal out of it, i will stop. And without ABS.
In the wet, i will experience only a little ABS.

Make of that what you will.

You may even be on to something.
Found some interesting research here:
http://autospeed.com.au/cms/title_Tyres-Grip-and-All-That/A_108915/article.html

pajo1981

pajo1981 wrote: »

The bit about colder liquid being denser is bollocks anyway- just ask any junior cert science student. FFS.

Jimmy Garlic wrote: »

Did you ever store vodka in a freezer?. When you pour it it is noticeably denser.

Temperature does indeed have an effect on the density of liquids, cool water down to 4 deg cel and the density increases, keep cooling it to below 4 deg cel and it will decrease in density again. At about 4 degwater begins to change state. Generally the cooler a liquid gets the more dense it gets.

Jimmy Garlic

RoverJames wrote: »

Temperature does indeed have an effect on the density of liquids, cool water down to 4 deg cel and the density increases, keep cooling it to below 4 deg cel and it will decrease in density again. At about 4 degwater begins to change state. Generally the cooler a liquid gets the more dense it gets.

The gel point of diesel is about -10c. That is why in Norway, Sweden etc they add kerosene I think? to make it less viscous in cold temps.

dr.fuzzenstein

RoverJames wrote: »

Temperature does indeed have an effect on the density of liquids, cool water down to 4 deg cel and the density increases, keep cooling it to below 4 deg cel and it will decrease in density again. At about 4 degwater begins to change state. Generally the cooler a liquid gets the more dense it gets.

There must be something to it, in the 80's F1 used to refuel with frozen fuel.
It was banned in 1985.
http://www.4mula1.ro/history/article/article10.html

Ronnie Beck

Roughly there is a 0.8 litre difference between 30 litres delivered at 0 deg. and the same delivered at 28 deg. In theory you get more fuel in winter than in summer. Knowing fuel companies they probably adjust their prices to compensate anyway. Daily the difference would be FA between morning and evening in this country where temperature ranges are alot smaller than in california.

Discodog

Fuel is in underground tanks & given the huge volume, I bet that it's temperature hardly varies.

Pkiernan

Pump up the tyres to 55 psi.

Jimmy Garlic

Pkiernan wrote: »

Pump up the tyres to 55 psi.

That would be insanity.