Fuel expansion with temp = less m.p.g.?.

It depends upon a lot of factors.

Higher temperature fuel will mean less energy per unit fuel volume (negative factor).

Higher temperature air will mean lower air viscosity and lower drag (positive factor).

Higher tyre temperature will mean higher tyre pressure and less rubber on the road (positive factor).

Higher road temperature will mean more grip (negative factor).

Higher tyre temperature will mean softer rubber and more grip (negative factor).

Higher temperature air will mean higher engine temperatures and lower thermodynamic efficiency (negative factor).

Higher engine temperature will mean lower lubricant viscosity (positive factor).

Etc., etc.....

Everything PW said is correct, but that said, with all things being equal and the only change is the temp. of the fuel, yes, you will get a slightly better mpg.

All things being equal, you would get less MPG with higher temperature fuel, as it is less dense. Fuel pumps measure volume and are calibrated at a set temperature (15C where I live), so if the temperature is above that you are getting less mass of fuel than you have paid for. Conversly, when the temp is below 15C you get more mass of fuel than you have paid for!

I don't think it makes much difference what time of day you buy the fuel, as it is usually stored in underground tanks, so the day to day temperature change is minimal.

Now if the question is for a given mass of fuel, will you get more MPG if it is hotter, that I cannot answer!

Have a good one

IPG

The energy content of gasoline is determined by its mass. So if you buy by volume, you get more energy per dollar if the gasoline is cool rather than warm.

Thanks for the answers Blokes- by my interpretation then I(or anyone), should, if calculating m.p.g.- Precisely WEIGH the fuel!.

I think CR4 and other users must insist on cool petrol.

Imagine the ads "the coolest petrol in the world".

Using cooled petrol will not be viable.

They will have to increase the price to maintain profit levels and for additional costs for cooling.

Each car would also require a cooler. At 35°C the tank will soon overflow.

The best advice would be to calculate a factor for consumption for example at 5°C.

That would impress the listners.

Higher temperature fuel will give better gas mileage because the gas will be more volitized and uniformly distributed. Henry "Smokey" yunick of NASCAR fame designed, built, and patented a Hot Air engine which heated the air/fuel charge to over 400 degrees F before igniting it using waste heat from the coolant and exhaust, and a modified turbocharger to act as a one way valve to keep expanding gas and air going towards the cylinders. He tested it in a pontiac fiero 2.5L "Iron Duke" 4 cyl engine and achived nearly 300 HP and 100 MPG. This car was actually featured in a number of automotive magazines back in the mid 1980's. The real trick is maintaining the constant volume of air/fuel going to your cylinders and adjusting your timing to prevent detonation. There have been a number of other people who have experimented with it over the years and I'm sure if you do a google search for "Hot-Air" or "Adiabatic" engine you'll find some results. Its interesting to note that by recycling waste heat to help vaporize the fuel, you're improving engine thermodynamic efficiency, and by pressurizing the air/fuel charge, you increase volumetric efficiency. Smokeys Fiero was so efficient, he was able to remove the radiator completely. The only drawback to his engine, and the reason it inst more widely employed today, was it emitted high numbers of NO_x emissions due to the higher temps.

But beyond this tangent, anything you can do to improve fuel volitillity will improve gas mileage. Belive it or not, not all of your fuel actually burns in the cylinders. If you or a friend is into cars, someday look at an engine running with open exhaust headers. You'll see flames shooting out as you increase the RPMs. If all the fuel and oxygen were consumed in the cylinders to produce power, you wouldnt see flames shooting out the exhaust.

There are those who thought of Smokey Yunick as something other than a cheater, but many who considered his numerous racing violations to be just plain cheating. For example, he would remove the ring gear from a flywheel to drill radial lightening holes into it, and then reinstall the ring gear, so the holes would be undetectable. Lightened flywheels were specifically prohibited. He even built a 7/8 scale car to race as if it were full scale! That others cheated too, is no excuse. NASCAR evolved out of moonshining. To expect honesty from early NASCAR racers would be a stretch.

Although he called his turbocharger a "homogenizer" to mislead people into thinking it was something new, his patent makes it clear that it is simply a turbocharger, and the patent cites boosts of 10 psi and 21 psi -- and the power outputs quoted in the patent are in line with those boost pressures. If an intercooler were used (instead of an interheater) the outputs would have been higher. The power figures quoted in the patent are lower than those of the highly reliable ordinary production engines of today: the patent claims 190 hp from 2.0 liters, whereas a Saab 2.0 liter gets 210hp with very high reliability. (The disparity is probably far greater than that, because the Saab figures are net, while Smokey's figures are no doubt gross.)

His Fiero was simply badly turbocharged and suffered from detonation, as would be expected from using a heater where an intercooler should be used. Even a good turbocharger installation does not improve the specific efficiency (mass of fuel used per horsepower-hour produced) of a spark ignition engine -- it simply causes the engine to produce more power, while using more fuel. (BSFC remains the same, or even drops slightly with turbocharging.) (Thus, if you compare the fuel mileage of a turbocharged Volvo s60 and a the (normally aspirated) BMW 330, you'll find them nearly the same.) Therefore, his claim of 100 mpg is ludicrous. 25% is typical spark ignition efficiency. To increase the Fiero's fuel efficiency by a factor of 4 (from the stock 25 mpg) would require 100% efficiency. Nothing suggests that such efficiency is possible in a spark ignition engine, and Smokey's claims for 100 mph efficiency were never verified by independent testing. Heating the intake charge lowers efficiency; it does not improve it. It degrades both volumetric and thermodynamic efficiency.

Only fuel vapor burns. Therefore if you see flames coming out of an exhaust header you are seeing fuel vapor burning, not liquid fuel. Such flames are an indication of engine inefficiency, but have nothing to do with the degree of vaporization, and can be seen on engines running on gasses, such as natural gas.

In an ordinary, modern engine with O2 sensor, 99% of the fuel is completely burned within the cylinder, leaving just enough unburned to keep the catalytic converter working. If we weren't worried about emissions, 100% could be burned within the cylinder -- its simply a matter of reprogramming the injection so that there is always a little excess O2 at the sensor.

Odd: The graphic I though I pasted above was a system diagram of the Yunick turbocharging system. Ill try this:

And while Smokey Yunick was running his car on hot fuel, the dragsters running fuel through 'cool cans' were winning the races! Go figure.

I remember Jeremy Clarkson doing an episode where he drove an Audi A8 diesel from London to Edinburgh and back again, on one tank of fuel. This is 800 miles and he made it just. He said to fill up very early on a cold morning would give you more fuel in the tank as it had shrunk a bit.

Funny as the car did about 30something miles with the computer telling him he could not go any further.

From the standpoint that an automobile, or other piece of equipment requires a given amount of energy (ie: fuel) to operate effectively, I would expect not. Perhaps increasing the temperature of the fuel will increase it's vapor pressure and distrubution within the cylinder (which might improve fuel efficiency), but major differences in I wouldnt expect.

Unfortunately, fuel is sold by volume (gal), while energy production capability is rated in weight (lbs). Since density is the weight/unit volume, it plays a part in the equation. Inceasing the temperature of a fuel reduces its density which results in less energy being delivered/ unit volume. Hence more volume of fuel is required.

thanks for answers Guys- my situation is I want to know whether the electrolizer I have used for the past 90,000 km is actually giving me 7% mpg extra- which every test confirms(such as disconnect)- or I am being fooled by expansion of fuel!. I must state that I put a measured amount of fuel into tank & run car till stops- then odometer reading is recorded- I also run over the same destinations, at the same speed/load- obviously ambient temp/conditions are beyond my control- I buy the fuel at the same outlet, same brand, about the same time(midday). My point is that if my fuel pump inlet can,t find fuel, the car stops(& yes, I do make sure the levels are the same at stop-ie flat level). I do remember Smokey who seemed to know it all (was it Popular Mechanics?)- reminds me of the tale my father told me of indigenous australians who, if car stopped(out of fuel) would urinate into tank- the water raised the remaining fuel to where the pump could pick it up!.

Here is a blog re the "hot gas" issue, which was in the press a few months ago.

I agree with the blogger, that with underground tanks, the fuel temp is too consistent (55 f, typically) to have an affect. The coefficient of expansion is .069% per degree f, so if the gasoline is 10 degrees hotter than the calibration temp (which is 60f) then it will have .7% more volume. So when you buy $3.00 dollars worth of 70 degree gas, you are getting $2.98 worth of energy. However, in the winter, the situation is reversed, so it all cancels out. It would be very rare (right after tank filling from a hot truck) that gasoline temp could reach 70f. (Although I think Dennis Kucinich has some good ideas, this alarmist study is not his best work. 90 degree gasoline??? Where?)

In a diesel, you can improve performance by adding propane or hydrogen to the intake air stream. A 7% improvement would be larger than expected, even if the gas came from a source that did not consume engine power. Given that hydrogen is generated at a net loss, the extra alternator load on the engine would exceed the btu value of the generated hydrogen, particularly because automotive alternators are very inefficient (60-65%) as compared with many other motors and generators. Electrolysis is rarely more than 75% efficient, even in expensive commercial electrolyzers, so the best you could hope for would be 49% as many hp from the H2/O2 mix as you use to drive the alternator. However, there can be a catalysing effect in diesels that can compensate for this loss.

You'd need to run through about 30 tanks with the thing connected, and 30 tanks with it disconnected (alternating, so engine wear, weather effects, driving conditions would even out) to get an idea of overall efficiency. But to really know, the test would have to be done on a dynamometer, with accurate fuel flow instrumentation. A 7% difference (the difference between 14 mpg and 15 mpg) is too close to reliably measure with road tests.

Thanks for answer Ken- 2 days ago I ran an experiment to measure expansion of petrol- I put 300ml of petrol in a glass bottle(mt beer stubby!)- measured temp with internal probe= 16'C- put bottle in open electric kettle in water & heated up monitoring temp in petrol- at 39'C removed bottle & measured volume= 305ml= 1.66% expansion. The next day(Sunday), having the previous day set up, I drove the car using a 1litre container of petrol pumped to the carby by an electric fuel pump until the car stopped- container & float chamber mt. Results; start from cold, electroliser off= 10km. #2- car warmed- electroliser off= 13.8km. #3- electroliser on- pulling 4.6A(electrolyte cold)= 13.1km. #4- electrolyte warm- pulling 10A= 10.4km. # 5- electroliser disconnected-= 15.2km. # 6- GRABBED ELECTROLISER & THREW TO THE S----HSE!!!> I think that I was fooled by running the tank to mt & assuming that was mt- but obviously, a large flat tank depending on the angle, as determined by the road slope, can have fuel away from the pump pick-up- I realise this now- & am sorry for my earlier endorsement of electrolisers- they are utter CRAP & COST POWER!!!. At least my device was home-made so cost me nothing- unlike the devices on sale!.

Thanks for relaying your story, Neil. That you took the initiative and made the effort to install the electrolyser in the first place is impressive, and then to follow through with the experiment is doubly impressive. As Edison said: "I have not failed. I've just found 10,000 ways that do not work."

The fuel economy world has been hard to navigate for many years. In the US, the EPA tests many add-on devices and has yet to find one that works as advertised. I find it especially troublesome when major periodicals support people whole-heartedly who, given just a reasonable review (let alone a serious, skeptical, scientific one) would have to be seen a frauds. Fast Company magazine (for entrepreneurs) just ran a large cover story article on a guy who claims to be able to make your Hummer (!!!???) get 100 mpg. The big gain, ostensibly, comes from converting from gasoline engines to a Duramax diesel. The article fails entirely to note the fact that many Hummers were sold as diesels (all the early ones were) and some of the late ones had turbocharged Duramax diesels very similar to the promoter's engine. They all get rotten mileage, not even remotely close to 20 mpg. An additional gain, the promoter claims, comes from adding hydrogen to the intake air. (Reasonably, this could be expected to improve fuel efficiency to perhaps 15 mpg from 14 -- at a ratio where the additional cost of the hydrogen doesn't outweigh the gain in mileage. Obviously, if you add enough hydrogen you can say you're not using any diesel fuel at all -- you are simply running the diesel on a horribly expensive, hard to handle, gas.) The article shows no effort at all in asking "Does a 100mpg Hummer seem plausible, or reasonable?" So the people who sell electrolysers now have a friend in Fast Company magazine. They can say "If this guy is getting 100 mpg in a Hummer, imagine what you can get in your Chevy Malibu: 200? You could save enough in a couple months to pay for the reasonable $200 cost." (of our $10 worth of hardware.)

Fortunately, the world has people like you who are willing to ask the questions and do the testing. Thanks.