[iamitp]

Sorry, if this the wrong thread for my question. I did go through some older relevant threads but couldn't come to a conclusion.

Is there a proven benefit for non-super cars from fuelling with premium grade petrol? I am talking about petrol with additives such as BPCL's Speed, IOCL's Xtrapremium and HPCL's Power? Has anyone conducted a scientific road test that can be referred to?

[Jeroen]

Originally Posted by iamitp

Is there a proven benefit for non-super cars from fuelling with premium grade petrol? I am talking about petrol with additives such as BPCL's Speed, IOCL's Xtrapremium and HPCL's Power? Has anyone conducted a scientific road test that can be referred to?

The simple short answer is no. You don’t need to conduct scientific road test because the basics are down to simple chemistry and thermodynamics.

All types of car petrol fuels have an almost identical specific energy. So in theory how much energy can be extracted from a high or a low octane fuel is the same.

But a high octane fuel allows the engine designer to use a higher compression ratio. It is the higher compression ratio that ensures that the air/fuel mixture reaches higher pressure and temperature. It is these higher pressure and temperature that create a better thermodynamic efficiency. In other words a larger percentage of the fuels (heat) energy gets converted into motive power. That could materialise as more power/torque and or fuel efficiency.

In an ideal world you would like to see the highest compression ratio possible (one of the reason diesel are more fuel efficient, they have higher compression ratio than fuel engines).

However, fuel when injected into the compressed and hot temperature will start to self ignite (like diesel) if the temperature is too high.It is commonly referred to as knocking. Small pockets of the fuel/air mixture start to prematurely ignite. This reduces fuel efficiency and power. More importantly it will actually damage the engineSo what the fuel companies do, they essentially raise the self ignition temperature of the fuel. In essence that is what the Octane number refers too.

Engines can adjust the air/fuel mixture as well as the ignition timing. So to some extend the engine designer can also control at what exact moment a spark is introduced to get the most efficient combustion. Many modern engines have knock sensors. So they are able to measure, per cilinder, knocking effects and adjust the timing a bit to minimise any effects.

So the most important aspect is the compression ratio of an engine. That determines to a large extend the thermodynamic efficiency of an engine. Engines get produced with a given/fixed compression ratio. It can not be changed. (Exceptions are a few very special engines and of course Octane test comparison engines).

So if an engine is designed for a fuel with for instance Octane number 93, putting Octane 100 in it is unlikely to produce any substantial advantages. Because due to its fixed compression ratio the temperature in the cilinder does not change at all. In order to get the potential advantages of the Octane 100 you need a higher compression ratio, which gives you the higher temperature, which gives you the higher thermodynamic efficiency.

Conversely, if an engine was to be designed for Octane 100 to start with and you would run it on Octane 93, you are likely to have problems. Due to its high compression and low octane fuel knocking is likely to occur.

Within a certain bandwith the ECU might be able to adjust, but this will differ largely from engine to engine.

You will find hundreds if not thousands of test on YouTube and in car magazines on this very topic. The outcome is by and large the same. Either there is very little effect or none at all. In most cases when you put premium fuel in an engine that was designed to run on regular you will see very little difference. Or the the differences are so small that it really does not warrant to pay a premium over regular fuel.

So high octane fuels are only meant for high compression engine, specifically designed for these fuels.

You will see some variations as car dealers need to cater for different fuels around the world. With sometimes different rating systems for the Octane number as well. And of course, they will try to do so, with minimum adjustments on each car.

To summarise: Putting high Octane fuel in regular cars (i.e. cars that are specified for regular fuel) is unlikely to produce any meaningful effects. It doesn’t harm the engine, only your wallet. Lots of people out on the net claiming it does, but that is just ego boosting. If you pay a premium you will want to see a difference and they will claim so.

On a car designed specifically for high Octane fuel, you should not put low Octane fuel in under any circumstance. Performance will degrade, more importantly you are likely to cause engine damage due to knocking.

Hope this helps.

Jeroen

[dealer]

Is there a way to find out what exact outlets sell xp100? I run power99+2 bottles of proctane currently due to my car running a tune and 11:1 compression ratio. (it's excessive i know but i get knocks and timing corrections even when solely using power99)

I would like to fill up 10 liters to see how it performs with the 95 RON and 98 RON maps available. Curious to see the price in Jaipur since delhi is Rs.160/litre

[iamitp]

Originally Posted by Jeroen

The simple short answer is no. You don’t need to conduct scientific road test because the basics are down to simple chemistry and thermodynamics.

Thanks for the definitive explanation, Jeroen

[SnS_12]

The biggest problem of filling high octane fuel is not the cost but the availability. You can’t mix high octane fuel with regular fuel as it would be a complete waste of money, but unless you only ride/drive between two pumps which sell these fuels the chances are you will have no option but to top up the tank with regular fuel.

Also, a good video to understand the difference between regular and high octane fuel and what actually pushes up the cost

https://youtu.be/1omRpYdEgGo

[saikarthik]

OK, It is good to read about all the technical details and miniscule improvement in the performance or reliability. But in my humble opinion,

1. Even if you own a supercar and it is tuned to produce more with higher octane fuel. Think about this - are you a competitive race driver who are at the limit of your supercar abilities and even after milking every ounce of the performance you feel you need more? if no - then better to enjoy the fun on tracks and try to improve the driving skills than impulsively buying a higher price fuel for no use. and for reliability, good maintenance and listening to your car's needs might be more productive.
* - applicable for mass market supercars (mass market -, I am gonna be trolled), not applicable for a Ferrari FXX or other track only cars.

2. For regular car users - fill good unadulterated fuel and maintain it well, in my 10 years of driving (stating humbly), I have not been affected by knocking! I don't know if it varies with temperature of the place you stay. You can very well save money to but a better car with this pricing (pun intended, but true too), or drive almost twice the distance - increases budget to accommodate longer trips and comfortable stays.

[Jeroen]

Just to add some more insights into the myths of high octane fuel. It should bring much better fuel efficiency.

As I mentioned earlier higher compression by definition gives you higher overall thermo dynamic efficiency. Have a look at this graph: This is a theoretical best approach.



Most cars/engines which are aimed/designed for Octane number 95 (regular fuel) are somewhere in the neighbourhood of a compression ratio of 10 (give or take).

Some high performance cars like maybe certain Porsches and some Ferrari’s might be at 12, max 14.

You can see that the curve really flattens out at a compression ratio of 10.

But to my earlier post; your engine has a fixed compression ratio anyway, higher octane does not affect compression ratio. In order to get the advantages you need to start with an engine with higher compression ratio. On existing cars and engine, that means enter the realms of the engine tuner.

Jeroen

[ZenMaster]

A video I recently came across, that explains why premium fuel is usually a waste of money unless the manufacturer explicitly advices against using normal 87-95 octane fuel.

https://youtu.be/28_a4mmsQ8Y

[Stribog]

Originally Posted by iliketurtles

Be right back. I’d rather smoke rubber than whatever special stuff these guys are on a steady diet of.

Given that the target market are the super luxury car owners (I mean if I want to fill it in my 20l beater, that is on me), and am guessing we are talking cars in the bracket of 60-70L upwards, is price of fuel even a factor for this 0.001% group?

[Stribog]

Originally Posted by Jeroen

To summarise: Putting high Octane fuel in regular cars (i.e. cars that are specified for regular fuel) is unlikely to produce any meaningful effects. It doesn’t harm the engine, only your wallet. Lots of people out on the net claiming it does, but that is just ego boosting. If you pay a premium you will want to see a difference and they will claim so.

Hope this helps.

Jeroen

Neat explanation - how about the additive extra 'special' diesels that the likes of Shell Power sell, any value in these?

I have a tuning box in my car, and so many mixed / confusing articles on the internet on this subject. Some say, for cars with tuning boxes, diesels with additives are good because of something to do with Soot, and some say it won't make a difference and some say there will be negative impact.

What is the scientific verdict?

[Jeroen]

Originally Posted by Stribog

Neat explanation - how about the additive extra 'special' diesels that the likes of Shell Power sell, any value in these?

Just to be clear; Every single fuel out there, be it petrol or diesel, has multiple additives. The differences between the various brands are minimal in my opinion.

We used to have a very large fleet of company cars. Leasing companies have better data on actual mileage and fuel usage than anybody else. Whenever we were discussing the fuel part of our contracts, they always said go for the cheapest fuel from the main brands. They could not find any advantages, be it in fuel usage, or car/engine maintenance, related to specific brand. Obviously, you need to get the correct type of fuel, (e.g. unleaded, a certain octane number etc) but the brand here in Europe doesn’t make the slightest bit of difference.

Originally Posted by Stribog

I have a tuning box in my car, and so many mixed / confusing articles on the internet on this subject. Some say, for cars with tuning boxes, diesels with additives are good because of something to do with Soot, and some say it won't make a difference and some say there will be negative impact.

As far as I am concerned all bets are off when you start tuning an engine. There are very capable engine tuners out there, but few have the means to actually measure long term impact of a tune up on an engine.

It really does depend on the engine and the tune up too. There are some engines out there, that are basically sold in different variants and all it is, is a software/parameter change. E.g. VW. If you buy the cheap version and get it tuned to the uprated version by a tuner, it is all still completely within normal specifications. So I would not see the need to change anything to the fuel.

To put it differently; I would think you would need to tune way outside the normal specification before the needs for a different fuel / additive arises.

Any tuning that produces additional soot, I would frown upon, irrespective. Something is not right.

Jeroen

[iliketurtles]

Originally Posted by Stribog

Given that the target market are the super luxury car owners (I mean if I want to fill it in my 20l beater, that is on me), and am guessing we are talking cars in the bracket of 60-70L upwards, is price of fuel even a factor for this 0.001% group?

Absolutely not, that's more for us mango people. But there is a bit of diminishing marginal utility at play here for sure, outside of the pure price consideration.

Assuming that 99 Octane is about 96 RON, and you're aiming for a minimum of 98 RON, why not pair up something like a bottle of Proctane your tankup of 99 Octane (about ₹102 a litre in Delhi ). Even if you do two bottles of Proctane at ₹600 apiece with a 50 liter tankup, it's a whole lot cheaper than getting a tankful of 100 Octane.

The economics simply don't add up, and even outside of that, when there's no noticeable difference in RON value after boosting up 97/99 with additives, how can anyone make an argument to go with 100 octane? This new-fangled fuel will struggle to make a case for itself.

I don't pretend to speak for those with supercars/sportscars, but I do fill 97/99 in my 328i, and this is just how I see it. Fill up 97/99, and top it up with an additive if I'm going to really be driving hard on the weekend with buddies or otherwise. 100 octane is a big, big step up in price, and I genuinely am stumped as to why it costs so much more.

[Stribog]

Originally Posted by Jeroen

It really does depend on the engine and the tune up too. There are some engines out there, that are basically sold in different variants and all it is, is a software/parameter change. E.g. VW. If you buy the cheap version and get it tuned to the uprated version by a tuner, it is all still completely within normal specifications. So I would not see the need to change anything to the fuel.

To put it differently; I would think you would need to tune way outside the normal specification before the needs for a different fuel / additive arises.

Any tuning that produces additional soot, I would frown upon, irrespective. Something is not right.

Jeroen

For academic interest, then is there any value to fuels like Shell Power Diesel etc? Or is it just marketing gimmicks?

[Jeroen]

Originally Posted by Stribog

For academic interest, then is there any value to fuels like Shell Power Diesel etc? Or is it just marketing gimmicks?

Primarily marketing gimmick. I mean if you are selling diesel fuel, what is your elevator pitch? You have to come up with something. There might be some truth in it, but in reality it is so small that it is negligible and other factors have a far bigger impact.

All fuel brands continuously update their various fuels. So you might see some very small difference between different brands from time to time as well.

I have come across various diesel fuel efficiencies comparison test by various car magazines. And they always come to the same overal conclussion; A certain brand of diesel fuel might give a slightly better fuel consumption, but it is never worth paying the extra amount for.

But today Shell might give you that minute advantage, tomorrow it could be another brand.

When it comes to diesel there really is no case at all for fuel efficiency one brand over the other. On maintenance, contamination, soot deposit etc? In all honesty I don’t know. I can’t recall ever coming across a good comparison test. I see the remarks of some people who claim to see “unbelievable” results when they took their engine apart.

My thought: as with fuel efficiency, the extend of contamination of your engine is mostly due to proper (or lack of) maintenance and your right foot. Those are the big levers that move the needle over time. Everything else is going to be very minor in comparison. Regardless.

If you drive your diesel mostly on long drives, good speeds, your engine is going to look cleaner at 50.000 km then a diesel that did 50.000 km in only short city hops. No matter what brand of fuel you would have put into the tank.

Jeroen

[aghate]

Originally Posted by Stribog

For academic interest, then is there any value to fuels like Shell Power Diesel etc? Or is it just marketing gimmicks?

From personal experience, I have used Shell V-Power Diesel and the normal diesel in my Mondeo. Initially I was getting 50 MPG on normal diesel. Once I started using V-Power the MPG jumped to 53. There was a noticeable difference in the amount of black smoke on harder accelerations.

It should be noted that majority of my driving is on Highways and hence I could sense more difference with high mileage trips over 2+ years. There is some advantage over the longer term for premium fuel if not over a few weeks. Hope this helps.