[anupmathur]

Originally Posted by SS-Traveller

1. Do premium fuels give up to 5% better FE or performance? If yes, why - i.e. by what mechanical/chemical/miraculous mechanism? If no, then why charge premium prices on these fuels?

I can think of one reason why premium fuel might give better FE: If an engine has a high compression ratio lower octane fuels would cause pre-mature detonation and that is wasteful. Obviously the FE will suffer, because the engine is unable to derive and correctly deploy the full energy from the fuel.

However, I am keen to know whether premium fuels are richer in calorific value.

[alpha1]

This is with respect to ppl suspecting if Oil companies are adding MMT and other additives to increase the Octane number.

I don't know from the oil distribution side, but from the refinery side, producing higher octane gas is pretty simple. You don't really need to add any additive.

There are many processes and units in refinery that produce gasoline.
And each one produces a characteristic product that has its own properties.
Finally each component is blended to meet the specifications.

Now the different "gasolines" from a refinery are:
1. Straight run - comes from distillation of crude. Most useless form. Has octane no around 60-70. Used primarily as fuel to gas turbines and as feedstock to petrochemicals and fertilizer plants. Most ppl know this as naphtha.

2. cracked naptha - comes from FCC and OHC plants. This has octane number in orders of 85-90. All refineries in India have one of these units. Hence everyone is so comfortable producing till 89-91 RON gasoline.

3. isomerate - comes from ISOM plant. This isomerizes light fractions of straight run naptha. Produces 90-95 octane gasoline. Most refineries in India are putting up plants. And by 2010 they will be up and running.

4. Reformate - comes from reformer plant, wherein heavy fractions of straight run naptha changes its structure and produces aromatics (like toluene, benzene, xylene etc). Usually benzene is removed (its carcinogenic, as well as it is a valuable feed to aromatic petrochemicals like LAB). This gasoline is 95-97 RON. Many of Indian refineries already have this units. Few are setting up new ones (again by 2010)

Now by blending all these different components - you can get the desired RON gasoline for selling. I don't see why anyone should add some other chemical to it.

Originally Posted by Bubby

The exmaples are :::

In my AVEO when I use normal Petrol I get a FE of 11kmpl, whereas with premium I get 12.5-13kmpl.

In my PALIO when I use normal Diesel I get a FE of 18kmpl, whereas with premium I get 21kmpl.

All figures are from my daily commute from home-work-home, 66kms a day, the start times ( the traffic scene ) are the same in all cases.

That might be because your engine is able to take loads at lower revs when its guzzling higher octane fuel compared to lower ocatane fuel.
As a result of which, you are able to shift to higher gears quicker.

[anupmathur]

Gosh, this is an amazing thread! Ask a simple question and have a ton of industry jargon thrown at you!
Are there no simplified answers that a layman could begin to understand?
Or is the situation best handled by confusing the issue to a point where no questions should be asked?

Does premium fuel, as sold to us at our bunks, have more calorific value than regular?
Does calorific value play a part in determining FE? Or is it of no consequence?

[jayakumarkp]

Hi Alpha,
That makes sense to me now. My uncle owns and runs two petrol pumps back in Kerala. He recommends normal petrol for the WagonR that we have at home. The reason he quotes is that nowadays these so called premium fuels are nothing but normal petrol + additives. These additives he said are added at the depot in proportions of one small bucket full to the tanker. As per him the premium fuel as of now is not really worth the extra one/two or more rupees/litre. He also said that before long these premium fuels used to be processed straight from the refineries(As pointed out by alpha1) but with the oil prices having gone up and most of the companies making losses they had stopped it and resorted to the additives method.

Am certainly not aware of whether they have all gone back to refinery processed premium fuel or not. (May b they have since oilprices have come down)

[Dr.Sumit Bhatti]

Originally Posted by Bubby

I always get better FE when I use premium fuels,

Originally Posted by anupmathur

How come I don't?

Originally Posted by Bubby

when I use normal Petrol I get a FE of 11kmpl, whereas with premium I get 12.5-13kmpl.

Originally Posted by getsurya

I do find the difference!

Originally Posted by SS-Traveller

Do premium fuels give up to 5% better FE or performance? If yes, why - i.e. by what mechanical/chemical/miraculous mechanism? can we have straight, short answers to these questions, We are depending on your knowledge to provide us simple answers on this forum, so please don't disappoint us.

Originally Posted by anupmathur

I can think of one reason why premium fuel might give better FE: If an engine has a high compression ratio
However, I am keen to know whether premium fuels are richer in calorific value.

Originally Posted by anupmathur

Does premium fuel, as sold to us at our bunks, have more calorific value than regular?
Does calorific value play a part in determining FE? Or is it of no consequence?

Originally Posted by jayakumarkp

That makes sense to me now. the premium fuel as of now is not really worth the extra one/two or more rupees/litre.

Originally Posted by alpha1

from the refinery side, producing higher octane gas is pretty simple. You don't really need to add any additive. each component is blended to meet the specifications.
Now by blending all these different components - you can get the desired RON gasoline for selling. I don't see why anyone should add some other chemical to it.
That might be because your engine is able to take loads at lower revs when its guzzling higher octane fuel compared to lower ocatane fuel.
As a result of which, you are able to shift to higher gears quicker.

Yes, Premium fuel can give higher calorific value. Each component of crude has different calorific value = energy content = heating value = heat of combustion. You can arrive at similar specifications with different (blends) combinations of crude component stock.
Fuel blends differ, therefore actual energy content (read: calorific value) varies from season to season and from batch to batch, by up to 4% more or less than the average, according to the US EPA.

An important point to note is that the RON specified is the minimum guaranteed ON for that batch of fuel. Earlier, only RON was specified for regular fuels, Today, MON is also specified. In the context of refining today, it is the minimum MON that is the most difficult constraint for the refiner. For example, to obtain a minimum 83 MON for a premium fuel, often RON is greater than 93, in actual practice it maybe 94 or even 95. However, declared RON values (PON) are fixed at 87, 89, 91, 93 97, 100, 102 and so on. So 91 ON premium may not be the same as 91 ON regular.(It may be higher).

Octane rating does not relate to the energy content of the fuel. It is only a measure of the fuel's tendency to burn rather than explode.

A fuel with a higher octane rating can be run at a higher compression ratio without detonating. Compression is directly related to power.

A common misconception is that power output or fuel mileage can be improved by burning higher octane fuel than a particular engine was designed for. The power output of an engine depends in part on the energy density of its fuel, but similar fuels with different octane ratings can have similar density. Since switching to a higher octane fuel does not add any more hydrocarbon content or oxygen, the engine cannot produce more power. However, FE will differ in this case due to engine tuning, the adaptability of the ECM/ECU, driving style, engine design, vehicle mass, fuel octane distribution (DON), fuel volatility, and the octane-enhancers used.

It might seem paradoxical that fuels with higher ON are used in more powerful engines, since such fuels 'detonate' less easily. An explosion in an ICE actually reduces power output, because most of the energy of combustion is absorbed as strain and heat in parts of the engine, instead of being converted to torque at the crankshaft. Consequently, an ideal 'burning' of a fuel results in maximum torque at the crankshaft and hence better FE.

CEP = Car Efficiency Parameter. Compression ratio and ignition timing determine engine performance (thermal efficiency and specific horsepower). Horsepower can be maintained by technological devices such as cylinder displacement and transmission ratios but the thermal efficiency always remains closely tied to the ON. A 6 ON increase (corresponding to an average difference between a premium fuel and a regular fuel) enables a 1 point gain in compression ratio (e.g. from 9 to 10), which results in a 6% efficiency improvement. An average 1% efficiency gain per point of ON increase is thereby obtained. For an engine with a compression ratio exactly adapted to the fuel used, the CEP represents the weight % change in consumption resulting from a 1 point change in ON. Here CEP = 1. Instead of compression ratio, if the ignition timing is advanced, CEP will be lower; between 0.5 and 1.
An increase in ON will always be an important factor for the thermal efficiency, thereby reducing the fuel consumption of motor vehicles. This fact alone justifies all the processes employed by the refiner to produce high ON fuels.

The VFM for the customer at current pricing is questionable.

(Sources: Petroleum Refining: Crude Oil, Wikipedia pages on Octane rating, Engine tuning, Heat of combustion, Heat engines )

[SS-Traveller]

Originally Posted by Dr.Sumit Bhatti

The VFM for the customer at current pricing is questionable.

Wonderfully lucid answer with a very clear single-line conclusion at the end. Thank you, Dr. Bhatti.

[anupmathur]

Originally Posted by SS-Traveller

Wonderfully lucid answer with a very clear single-line conclusion at the end. Thank you, Dr. Bhatti.

Indeed! Thank you, Dr. Bhatti, for one very clear answer!

So now, do we need to put a tiger in our tanks?!

[Dr.Sumit Bhatti]

This is with reference to an older thread http://www.team-bhp.com/forum/techni...ar-diesel.html and further discussion here:

1. Just like the blood that runs through your blood vessels, which is the same throughout your body, even though it is manufactured in various bone marrow sites across your body; the fuels that we buy in India from IndianOil Corporation Limited (IOCL), Hindustan Petroleum Corporation Limited (HPCL) and Bharat Petroleum Corporation Limited (BPCL) is the same.
2. The slight differences are from batch to batch during different production runs in the local refineries* and co-mingled product.
3. To avoid duplication in infrastructure, fuel is shared by all the PSU Oil Companies by various hospitality arrangements. This also applies to transport and pipelines.
4. For example, HPCL supplies all liquid fuels in and around Pune from it's Loni Depot which is linked by rail as well as pipeline to it's *Gandhar Oil Refinery and BPCL's Mahaul Oil Refinery in Mumbai; with HPCL's Vashi Oil Terminal / Tank Farm in between. It also supplies fuel further to Sholapur Depot. IOCL and BPCL in Pune get their supply from HPCL. Now IOCL has its own storage, while BPCL still does not. The Mumbai refineries also supply Manmad and further Indore via pipeline besides other locations by railroad. So technically all the fuel in these regions is the same. Product is also 'bridged' between depots by rail and road in supply / demand mismatch.
5. This is in line with what happens on the global scale.
6. Add to this the point that I have brought up in post # 66. All the additives are sourced from the same supplier,NewMarket Corporation and it's subsidiaries Afton Chemical Corporation (IOC) and Ethyl Corporation(BPC).
7. HPCL's source of additives is clouded in secrecy like Coca-Cola but probably is the same.
8. These additives are added just before supply.
9. So whether we buy Hi-Speed (BPC), XtraMile (IOC) or Turbojet (HPC) Diesel or Speed (BPC), XtraPremium (IOC) or Power (HPC) Petrol or for that matter even Regular Unleaded Petrol (ULP) or Low Sulphur High Speed (LSHS) Diesel from any PSU Petrol Pump, all these fuels are virtually the same as their respective counterparts!
10. So unless HPCL spring's up a surprise, there is no difference amongst these respective premium PSU 'branded fuels' !

[ask77]

slight diversion from quality of fuel question. Is it true that petrol becomes "stale" if kept for too long in the fuel tank like in a lpg or cng vehicle ? If so than to what period of time can petrol be kept ? Is there an "expiry date" for petrol ? Also what harm can be caused by stale petrol and are there any additives to control the long term stability of petrol ?

[tush]

Originally Posted by Dr.Sumit Bhatti

Since switching to a higher octane fuel does not add any more hydrocarbon content or oxygen, the engine cannot produce more power. However, FE will differ in this case due to engine tuning, the adaptability of the ECM/ECU, driving style, engine design, vehicle mass, fuel octane distribution (DON), fuel volatility, and the octane-enhancers used.

Wealth of knowledge in this thread. Thanks to all the experts to share their knowledge with all us bhpians.

Dr. Bhatti can you kindly explain me about the ECU thing that you have mentioned above. Does it mean ECM/ECU posses artificial intelligence to adapt itself to the fuel. I dont know if my question is correct but it just poped up in my mind

[Dr.Sumit Bhatti]

Originally Posted by ask77

slight diversion from quality of fuel question. Is it true that petrol becomes "stale" if kept for too long in the fuel tank like in a lpg or cng vehicle ? If so than to what period of time can petrol be kept ? Is there an "expiry date" for petrol ? Also what harm can be caused by stale petrol and are there any additives to control the long term stability of petrol ?

I think the answer is 10 days to a fortnight! Most sources say six months to two years, but let me build up this argument.

Crude Oil has been stable for up to half a billion years. Recent market pressures to increase yields like, for example, in the Reliance Petroleum Jamnagar oil refinery, which is one of the most complex refineries in the world and claims to process cheap, low-grade crude into petrol and diesel and vary output versus input as per demand with a Nelson Complexity Index of 14.

Older Petrol Dealers across the country have noticed rising handling loss from newer fuels which now contain more oxygenates, lighter fractions harvested from the same crude than earlier, and many more newer additives, ethanol and this fuel has undergone many more processes than earlier ‘straight run’ fuel. No explanation was ever given by any oil company regarding rising handling loss.

The storage life of petrol and diesel under ideal storage conditions is many years. The fuel may go ‘off-spec’ but it is still usable, better still, when mixed with fresh fuel.
Many senior BHP-ians will know about the Jerry Can.
Ideal storage conditions include:
1. Non-porous containers. (avoid plastic, use glass or aluminum).
2. Low ullage space. (Fill nine-tenth).
3. Airtight seal.
4. Avoid re-opening of containers.
5. Low temperature.
6. Low humidity.
7. Storage away of direct sunlight.
8. Extra stabilizers added, if long storage is anticipated. Also note that fuel stabilizers stabilize fuel, but cannot ‘repair’ stale fuel. Example: Sta-bil.
9. Absence of any hydrocarbon degrading bacteria.

Newer fuels seem to be more unstable, and some of the changes seen on long storage in less than ideal conditions are:
1. Loss of FEON by evaporation of lighter fractions. (Post #69 in this thread)
2. Oxidation leading to formation of gum and varnish.
3. Fractionation of Ethanol in the presence of moisture. (Please refer to post #18 in the thread http://www.team-bhp.com/forum/test-d...ernatives.html
4. Rust formation, also due to moisture, which is seen more in costal vehicles, especially those vehicles which are run on low fuel tank levels (high ullage space). Corrosion also occurs due to ethanol and due to sulphuric acid formation.
5. Darkening of color (due to oxidation and polymerization).
6. Distinct change in smell (Like solvent or paint thinner).

Such stale fuel will cause problems like:
1. Starting problems.
2. Knocking and engine damage.
3. Stalling and clogging up of filters, fuel lines and fuel injectors due to gum, varnish, rust, ethanol fractionation.
4. Excessive carbon deposits.
5. Low FE.
6. Emission norms failure.

Some of these points are incorporated in our own laws, while other interesting points come up:

According to The Motor Spirit and High Speed Diesel (Regulation of Supply and Distribution and Prevention of Malpractices) Order, 1998, Amended in 2001 and in 2005.

Section 5. Sampling of Product:

(2) Samples shall be taken in clean glass or aluminum containers. Plastic containers shall not be used for drawing samples.

(4) The authorized officer shall send the sample of the product taken under sub-clause (2) within 10 days to any of the laboratories mentioned in Schedule III


According to the Petroleum Rules, 2002 made under the Petroleum Act, 1934 (30 of 1934):
Chapter X: Testing of Petroleum:
186. Drawing of Sample. - (1) Where the sample is drawn from an original unopened receptacle containing petroleum otherwise than in bulk the opening shall be sufficient to admit of the sample being rapidly transferred from the receptacle.
(2) Two bottles, each of a capacity of 1 liter shall be filled to nine-tenths of their
capacity with the sample and corked. The corks shall be driven home and cut-off level with the neck; and melted sealing wax shall be worked into the corks and the bottles shall be efficiently sealed.


A reasonable guess is that with current ‘just-in-time’ inventory systems in refineries, fuel can be delivered within a few days to major cities and within a few weeks or up to three months for remote areas.

Average fuel life claimed by British Petroleum for ‘Ultimate’ brand petrol now is six months to one year. This might refer to an ‘expiry date’.

I think the above rule of 10 days for testing, (assuming that the laboratory tests immediately within a day) means fuel can become ‘off-spec’ rapidly. This has now gained more significance with the introduction of hybrid LPG /petrol vehicles where the petrol may lie in the tank for excessive periods of time.

The explanation given by oil companies in the past, regarding ‘off-spec’ results beyond 10 days is co-mingled product from multiple stock deliveries.

There’s probably more to this than meets the eye.

(Sources: Petroleum Act 1934, Petroleum Rules 2002, MS & HSD Control Order 1998/2001/2005, British Petroleum brochure on Ultimate Branded Petrol, The chemistry and technology of Petroleum, Sta-bil, Science Direct, Wikipedia pages on Nelson Complexity Index, Jerry Can, Petroleum, Crude Oil. )

[Dr.Sumit Bhatti]

Originally Posted by tush

Wealth of knowledge in this thread. Thanks to all the experts to share their knowledge with all us bhpians.

Dr. Bhatti can you kindly explain me about the ECU thing that you have mentioned above. Does it mean ECM/ECU posses artificial intelligence to adapt itself to the fuel. I dont know if my question is correct but it just poped up in my mind

AS you have mentioned, "Thanks to all the experts": Please refer to this excellent thread http://www.team-bhp.com/forum/techni...u-ecm-ems.html and read beginning from post #1 by dadu which rocks!

[adishell]

I would like to share from my experience On board ships.
Before refuelling we do the spot test(ie the filter paper test) and also check the quality by specific gravity of a sample of diesel, using the tables corresponding temperature of the Diesel and then match the results with the MDS(Material Data Sheet,which consists of details about the diesel supplied ie chemical composition,sulphur content, specific gravity@15Celsius,calorific value and also is a legal document) provided by the supplier.
Further a sample of the fuel is sent to the laboratory every time of refueling for more detailed test,of which we recieve the report and then only use the diesel.
Majority of the times the results of the spot test & Specific gravity Tables satisfactorily match the lab analysis.So these two methods are fairly reliable when you are refuelling 100,000L at a time

I used the same tests for the Shell Fuel Pump from where i refill my landy, the results were satisfactory. And Shell Pumps only have high speed diesel and the staff were very keen on the quality and quantity tests.

[Dr.Sumit Bhatti]

Originally Posted by adishell

I would like to share from my experience On board ships.
Before refuelling we do the spot test(ie the filter paper test) and also check the quality by specific gravity of a sample of diesel, using the tables corresponding temperature of the Diesel and then match the results with the MDS(Material Data Sheet,which consists of details about the diesel supplied ie chemical composition,sulphur content, specific gravity@15Celsius,calorific value and also is a legal document) provided by the supplier.
Further a sample of the fuel is sent to the laboratory every time of refueling for more detailed test,of which we recieve the report and then only use the diesel.
Majority of the times the results of the spot test & Specific gravity Tables satisfactorily match the lab analysis.So these two methods are fairly reliable when you are refuelling 100,000L at a time

I used the same tests for the Shell Fuel Pump from where i refill my landy, the results were satisfactory. And Shell Pumps only have high speed diesel and the staff were very keen on the quality and quantity tests.

Filter Paper Test for Petrol:

1. Select an appropriate clean Whatman No.1 or No. 2 white cellulose filter paper. Whatman filter paper is now a product of GE Healthcare. It is also available at all PSU petrol pumps on demand.

2. Clean the mouth of the nozzle to remove any stains.

3. Put a drop or two of petrol on the filter paper directly from the nozzle.

4. This petrol should evaporate in about 2 minutes without leaving a stain on the filter paper. (If the area of the filter paper where the drop of MS was put, remains pinkish, it is the colour of the petrol and not any stain)

5. If a stain is left on the filter paper, then there is a possibility of adulteration.

(Source: MOP&NG, GE Healthcare)

[mithun]

I've heard that Naphtha is mainly used in adulteration. Is that true ?