36 replies to this topic

[gsms]

So is the conclusion to use regular 95ron in an spi?

Guy.

[Jake Blues]

That's why it's not such a great idea on road cars, you want to be able to use any fuel if you really need to (like if you get to the only station for 50 miles and they're out of Optimax) and you want a smooth drive.

So what are you saying? Don't use Optimax etc on road cars? Why is it sold in garages then?

[Grayedout]

No I think he was saying don't get your engine tuned to rely on Optimax or equivalent in case you can't get it and have to use 95 RON. :grin:

[neil_g]

or buy a jerry can.

[Jake Blues]

No I think he was saying don't get your engine tuned to rely on Optimax or equivalent in case you can't get it and have to use 95 RON. :grin:

But we didn't do anything to the engine anyway.....just started putting it in :saywhat:
This seems to be contrary to what everyone else is asying about using better quality fuel.

[Grayedout]

Whoa !!!!

To summarise !! :tongue:

1. Yes Optimax etc WILL give you smoother running and better fuel economy no matter what state of tune your engine is in, due to the additves !

2. IF you want to take advantage of the higher Octane then you need to get your engine tuned to suit.....ie it will allow you to run more advanced timing without the risk of detonation and this will give you more power !!!!

So higher quality fuel WILL give smoother running and better economy. It can also give you more power but ONLY if you tune the engine to suit !!!!

If you want it explaining more then get me a beer at the Thong Run !!! :wink:

:grin: :grin: :grin:

[Dan]

Right, I'll try to be a bit clearer.

Yes, Optimax is a better quality fuel than generic unleaded. It has a higher octane number meaning it can be compressed further and get hotter before it starts to detonate. So if you tune your engine to get the very best performance possible out of Optimax it will always have to run on Optimax. This is why performance tuning centres say it isn't worth re-tuning an engine in a road car to get the best from high octane fuels as it's impracticle. The fuel isn't available everywhere and is kept in smaller quantities than other fuels and therefore runs out quicker so you may be forced to put in lower octane fuel at some point. If you put lower RON fuel in it it will start to detonate and could damage itself.
If you are building an out and ou ttrack car you can always control the exact type of fuel you use for the race, it's not the same environment as a road car. This will enable you to run the engine getting the absolute maximum potential out of it.
However as you get closer to the maximum tuning of the Optimax fuel it will start to behave more like the lower octane fuel does in a car designed to work with that fuel.
So if you are running Optimax in an SPi which as I said before has it's tuning fixed for 95 RON fuel you will feel that the engine is running much more smoothly and better as it's not running on the edge of it's performance envelope.
So if you like the way your car drives on Optimax and can afford it then use it but if you re-tune for it then while you will see another slight increase in performance remember you can't put in anything else.
It's like putting 4 star in a 2 star fuelled engine, it will run better.
Simple and none of that is at odds with what everyone else is saying.

[kada1980]

Found this on the Cupra website, quite interesting:

"I work with petrol companies, so i'll let you into some lesser known secrets.

Super unleaded is a fine fuel, but only if purchased from reputable dealers. Esso SUPER, like BP are about the best you can buy. Supermarket stuff is just 4 star without the valve addictive, which itself is just 95 unleaded that has been octane boosted. AVOID AT ALL COSTS. Supermarket petrol is a very dirty fuel. Any engineer of their pumps will confirm that.
I have seen the results of their filters and you get everything from feathers to god knows what flowing through supermarket fuels. EVEN SAND.

All Super by law has to be 97 ron, but where its stable enough to hold higher octane, stations are able to advertise its octane as being higher sometimes.

Optimax has a variable octane rating, due to its structure its less stable, but leaves the refinery at 101 octiane.
Thats the equivalent to the old 5 star for those old enough to remember it.
By the time you buy it, its closer to around 97.
This is why its octane isnt always stated.

Normal 95 or 97 fuels wont lose octane, whereas optimax does, but used fresh, its the highest octane fuel you can buy.

All supermarket fuels come from either the Matex or Purfleit refineries for the south east. These only take oil from the eastern block. They are most definately NOT the same fuels as ESSO and such like.
They also remix contaminations for other companies then sell the fuel on via supermarkets as well.
On average, each 50 litres brought from a supermarket will have 8% contaminates, and 9 grams of grit.
I have got 2 test tubes sitting on my desk at work of both ESSO and Tesco regular 95 for simple comparisons when arguing these points with supermarket buyers.
There is a bead in both which on the Tesco tube floats in mid suspension due to the grittiness of its petrol.
The ESSO falls straight to the bottom.
These are random samples taken every few weeks, and the results are always the same.

Texaco is a subsidary of ESSO and both use the same petrol.

There are basically 3 companies which supply fuel to the UK. ESSO, BP, AND SHELL.

Each sells to all the other names you find.

JET, FINA, Q8 and a few other smaller outlets all use SHELL.

TEXACO and TOTAL use ESSO,

Supermarkets use Eastern Block fuels, which are primarily designed for the 91 Ron continent market.
These are upgraded in the UK to UK specs by using Butane gas.
Hence to avoid.

BP Ultimate is just its old Super grade cleaned up a bit.
IE. It goes through another filter at the refinery.
Not a bad fuel though, second only to ESSO in quality.
Its Diesel is the best in the world for all you Diesel owners.

OPTICRAP. Need i say more. All grades supplied by Shell.
Might as well fill from your local FINA station and pop a bottle of Halfarts octane super duper booster plus in.

ESSO 95 and 97 = If you want every pennies worth in quality petrol, look no further.
Get it at your local TOTAL, TEXACO or ESSO now

[kada1980]

Some more interesting reading

[Jake Blues]

Right, I'll try to be a bit clearer.

So if you like the way your car drives on Optimax and can afford it then use it but if you re-tune for it then while you will see another slight increase in performance remember you can't put in anything else.

Simple and none of that is at odds with what everyone else is saying.

With all the talk on re-tuning....no one has said how to retune an engine with electronic ignition...so how do you?


(PS. On my Astra I got an increase in mpg from 33 on Tesco fuel to 42 on BP Ultimate which obviously works out to be cheaper in the long run per tank full)

[Grayedout]

no one has said how to retune an engine with electronic ignition

If its still got a distributer then the timing can be set the same as any other. If its a full distrubuter-less system then basically it can't without getting a modifed ECU unit !!!

[AlexM]

very interesting, its gonna be Esso from now on its 88.9 for regular at the mo which is only a touch more than Adsa or Morrisons, whats the Esso version of optimax called?

[Jammy]

Its Esso Energy I think?

[silvermini]

so we have now established that better petrol gives a smoother running more effecient car? mailny through additives and not the octane rating unless you have a highly tuned/ tuned specifically for one type of petrol

Have a browse clickedy click

[Jake Blues]

Blowed if I know now thanks to all the "clear things up" posts

That's the wonder of forum experts but bottom line is this....do my family's minis (Spi and carb) run better, faster, smoother and more economically on Ultimate or Optimax than ordinary or supermarket petrol?

Answer, without any science is yes!

Why? Additives, octane, burning rate, RON, tuning? Don't know and now don't care either
KISS....keep it simple stupid! :tongue: