Is it worth using high octane petty?

[pat_6_4]

I've been wondering if it's worth spending the extra pence (and giving Mr Brown more of my dollar) buying 97 or 99 octane fuel for my van rather than the bog standard 95.

Is there any difference in performance and fuel economy (which is my main concern at the moment)

I'm running a 2.0 litre Aircooled

Thanks for the input and advice

Cheers

[eatcustard]

Stay with the standard petrol
Only the 2.1 needs the 97 ron

[CovKid]

Yep, bear in mind that the bug engine ran on 3 star and the 2.0 Aircooled is only a minor step up from that.

[toomanytoys]

Not worth it.. IIRC the timing is set for 92 RON which we never got so is actually retarded for 95...

Correct to which engine needs 98 RON.. its the 2.1 "DJ" engines.. unless timing is retarded to 5 deg BTDC then you can use 95.. 2.1 "MV" engines are also set up to run on 92...

[72BUG]

I filled up on "posh petrol" the other day by accident. Should have looked at the pump more closely. 7p a litre extra and I didn't see any difference in either economy or performance. I'm also running a 2ltr Aircooled. I would say buy the cheapest stuff possible. I'm thinking on having mine converted to steam so I can run it off the treas in my back garden.

[pat_6_4]

Muchos gracias guys for the informative answers and will stick to the non-posh petty.

Not really understanding the retardation bit though.

cheers

p.s. does filling up on 97 ron affect retardation thingy?

[eatcustard]

Retarded ignition timing causes the ignition spark to occur later in an engine's cycle.
That has to be done manualy.
97 Petrol will not alter the timing.

[toomanytoys]

Using a higher quality grade (we'll call it "quality" as it simplifies it ) of fuel in an engine designed and set up for lower quality fuel, offers no advantage at all..

Here is a simplified explenation...

Basically the numbers (RON, used in Europe / MON, used in the USA) relate to a scale of "knock" ressistance ("pinking" in old money), the higher the number the better ressistance..
"Knock/pinking" is when the fuel ignites very quickly (too quickly), and/or prior to the spark igniting it, by the compression in the cylinder.. pinking eats away at pistons and heads and will destroy an engine pretty quickly.

High compression engines (eg "2.1 DJ") require a higher knock ressitance for the ignition timing they use, to get the power (2.1 DJ is rated at 112bhp) and to prevent engine damage from pinking. (hence a lot of high performance jap spec cars require the Tesco 99 fuel)

Oh LPG has a RON of around 110.. so thats why high performance engines work well on it..

I could go into the theory of prolonged use of a higher grade fuel causing damage to an engine, but thats another story..

[eatcustard]

I could go into the theory of prolonged use of a higher grade fuel causing damage to an engine, but thats another story..

Oh please do

Pulls up a chair and falls asleep

[horns]

My other car requires fancy petrol, and its a pain sometimes to have to drive around looking for a garage with some in the tanks. Consequently, I find the camper's love of the ubiquitous diesel an absolute pleasure by comparison.

[CovKid]

And the vw heritage in being able to start on the smell of an oily rag. With the exception of the 2.1 and diesel obviously, these engines will run on a lower octane than that being supplied at pumps. Unfortunately its no longer made.

[tezza]

not worth thinking about unless some bugger stuck a bmw m5 inthe back when you werent looking!!!

[Epiphone]

Hi, ive got the 2.1l SS (92 bhp), so should I be putting in 98 ocotane then? Ive mostly been putting in 92, and then recently, not sure if due to,

• only running it a few miles to the gym 3/4 times a week
  cold weather
  92 octane petrol
  

but the engine was really sounding like a tractor on low revs, meaning when changing gear too.

also was getting the tappets sound more, I guess due to the short trips, so went for a 30 mins drive last night, to get it going.

[quagmire]

i run my 2.1 on kittens tears or a mix of both normal and special petty and it runs well with loads of grunt.

[Red Westie]

Busting the BIG mith....high octane does not mean high power!

So why then (I here you ask) is it used in performance engines....easy!
High performance engines generally run hotter so are pre-disposed to pinking ie: (the heat in the cylinder causing the petrol to ignite before the spark occurs)

Remedy....
To use a higher octane petrol that RESISTS burning so basically can wait until the spark to ignite.

Simplezzzzz.
Martin