Which fuel ?

[jberks]

Hi all,
probably opening a hornets nest, but ...
For the last few months I have been using texaco for my twice weekly fill ups. Recently I've found performance to be sporadic, sometimes ok and sometimes a bit asthmatic. By chance last week I filled up at BP and felt there was a noticible difference. I went back to texaco (nearer) and it seemed to deteriorate. Filled up at BP again last night and it seemed smoother and more responsive this morning. My overactive imagination ?

 

[Myros]

fuel

I find that sometimes Asda premium unleaded feels as though it outperforms Sainsbury's Super unleaded, my normal choice. It depends on whether I have a price reduction voucher on which I choose. I was running Super + on the contintent and found it to be yet another level of performance we don't get here.

 

[mlc]

different fuels

Im always interested in these sort of comments.

My understanding is that all Petrol has to be to a minimum standard, and that all cars are designed to use fuel of that standard, therefore if the oil company provides "better" fuel then it will not provide an advantage. This means that putting the higher grade unleaded fuel in your car should make no difference.

Clearly additives that clean the system, help injectors etc. could improve the efficency of the engine, but this just means the engine is running correctly rather than that the fuel is producing more power.

Bottom line - I think people are getting conned.

Mark

 

[sbeatti]

Hmm. I think you are right about the hornets nest!
I'll be following this thread with interest. Having just bought my sports coupe I was asking my husband this very same question about fuel. Last car was a Clio so obviously it just got the bog standard unleaded. Other car is a diesel. I am looking to keep my coupe for some time so I wonder if it would be worth filling up with the more expensive stuff?
Sue

 

[dirtydiesel]

I run my merc on dirty red diesel @ £5 for 5 gallons dont know what the miles to the gallon i am getting all i do know the car goes like f**k when you see the customs & excise in sight. But i must admit it nice and cheap to run.

 

[500sl]

I run my merc on dirty red diesel @ £5 for 5 gallons dont know what the miles to the gallon i am getting all i do know the car goes like f**k when you see the customs & excise in sight. But i must admit it nice and cheap to run.

Ther's nothing wrong with red diesel ;some of the most expensive engines in the world run on it.. It is top quality diesel with a dye added. It works out at 30p a litre.

 

[jberks]

Not sure about that SL, i saw what it did to your Eclass. Powerful stuff !

 

[500sl]

Not sure about that SL, i saw what it did to your Eclass. Powerful stuff !

My eclass is petrol.It was just a minor weld problem....

 

[CoventGardenCabrio]

This has been much written about on this board. The octane rating of petrol indisputably has an effect on the car's performance and fuel economy (basically, the higher the octane rating, the better your performance and fuel economy).

BP Ultimate guarantee 97 RON and Shell Optimax is the only petrol in the UK to guarantee at least 98 RON. I use Optimax and definitely see a difference when I occasionally use other petrol. No such problem on the Continent where every forecourt sells 98+ RON petrol (as well as the standard 95 RON).

 

[jberks]

I have been testing out with BP 97 octane. It seems a little livelier (subjective) but I haven't seen any change in fuel consumption. Maybe I am taking advantage of the extra power !

 

[Caj]

I've been using Shell Optimax in my Sports Coupe for some time now. I used to use anything in the past but took the view that the car has cost me a lot of money and i'd rather run it on better quality fuel. It took about three tanks of Optimax to see the different. The throttle response is better and its much smoother and more lively. From people in the know, apparently Esso Super is the next best if you can't find a Shell garage.
I have tried BP Ultimate but found no difference.

My dad has even changed over and he's notice better fuel economy in his C-class. But he drives more conservatively than me!

 

[calum]

Having just sold my TVR - sniff - I can say that Shell Optimax seems to be the fuel of choice in that fraternity

 

[sgregory124]

Shell Optimax without a shadow of a doubt. Wouldn't touch the supermarket crap.

The car not only seems to run smoother but as someone pointed out, it also exhibits better throttle response (and low end grunt for that matter).

Plus it also appears to be much cleaner, I notice a distinct lack of soot on the exhaust tips on my car, certainly after a long run.

Simon

1997 C36 AMG

 

[GaryC]

I normally use Esso Super unleaded, but sometime, if no choce and low in tank, will go for Shell Optimax, I found both of them are very good.

Let talk aboiut Octane rating... Octane rating is an index to indicate how DIFFICULT the fuel be ignite by itself.

Sound complicated, but easy to explain, the higher the Octane rating, the harder the fuel to ignite by itself. The Octane number is the reverse of teh Cetane number in the Diesel. Diesel engine rely on High pressure and temperature diffusion burning, self ignition, so it require high Cetane number to effective burn the fuel.

For Petrol, the fuel is ignite by the spark, so we don't want it to ignite by itself before the spark, or the top dead centre (or nearly), so we need higher Octrane number. Low octane number (about 80 RON) fuel will ignite itself when the piston not reach the top dead centre. ie, if your car running on 10:1 compression ratio, with 80 Ron fuel, it will pre-ignite.

One of the factor affect the Power and Efficiency of an engine is the: 'Speed of flame', this mean how fast the flame goes, how fast the fuel particle be totally ignite, the faster, the better.

When a spark ignite the fuel particle, the flame will promote the burning to the other un-burn fuel particle, if the fuel with high octane number like 98 Ron, it will help to let the flame burn faster, as it could prevent the fuel be ignite by itself for a few micro second before the spark, (it will happen, but not quite noticible). So it could give you better throttle respond by increase the 'mean effect pressure'.

You could actually fine tune your engine ignition a bit later if you use 98 Ron fuel, so the compression ratio could be a bit higher, then, more power and better throttle respond.

 

[Notneb]

Which fuel?

I conducted a brief test as my Honda was not providing the usual MPG. Using BP/Shell fuel all was good. Using supermarket fuel with the exception of ASDA the MPG suffered dramatically to a point where the difference in price was such that the lower MPG did not make it cost effective. Hence now only use BP/Shell/ASDA but I am careful to note the price per litre.