Which petrol do you prefer?

[johnny74]

Just wondering what people's thoughts are on fuel. I have an 85 2 litre coupe that seems to be quite fussy. So far I've figured that it hates standard unleaded and seems to hate BP Ultimate, but goes quite well with V-power and Total Excellium. The fuel cap says min. 98 RON which seems quite picky.

Any thoughts?

[scotty33]

My 20v has 95 RON recommended, with a minimum of 91 RON. In theory, there is no performance advantage in me using 97+ RON. I posted my thoughts in this thread:http://www.vwaudiforum.co.uk/forum/showthread.php?p=68451#post68451

I used to have an 87 Audi 80 1.8. It too used 98 RON fuel, but you could adjust the timing for unleaded if required. They tell you doing this only loses you a couple of hp, they don't mention that it makes the car less responsive and thirstier!

[johnny74]

Cheers for pointing that thread out!

I'm quite happy using V-power as I don't do that many miles and I reckon I get an increase in mpg out of it that offsets that cost of the petrol. I just wish there were more Shell garages in Leicester - BP seem to outnumber Shell by 3 to 1.

Any idea why the older cars are supposed to be run on higher octane fuels? I mean 98 is hard to get at many petrol stations and I would have guessed it was rarer in 1985 than it is now.

[MalcQV]

Cheers for pointing that thread out!

Any idea why the older cars are supposed to be run on higher octane fuels? I mean 98 is hard to get at many petrol stations and I would have guessed it was rarer in 1985 than it is now.

In 1985 we still had leaded fuel, all petrol stations had it. 4 star and I think 3 star? going back a bit further you got 5 star which was 100 Octane I think.

I think with older cars is was due to the compression ratio, or I thought it was.

[onzarob]

4 star was 98 ron, when unleaded came out they dropped the octane to 91-95 ron!!!
5 star petrol was dropped in the 70's I think.

Super unleaded was brought in the 90's at 98ron then taxwd by the government more!!!! even though you can get more MPG for it..crazy.

It died out for a while now the new ultimate range on petrol are coming back but are more expensive due to tax!!!

[scotty33]

I'm with MalcQV, the compression ratio and the amount of ignition advance are related to octane requirement. This is why the timing can be retarded a few degrees (on some older cars), to allow use of 95 RON. Maybe yours is running slightly too much advance, or the piston crowns are coked up, which boosts compression, and can cause hot spots that can cause pre-ignition. Either way, if it's happy running on V-power, maybe try the Tesco 99? I will be:D

[MalcQV]

Might try the Tesco 99RON in my Passat as it is only 95.1p litre :beerchug: