99 Octane Fuel

[claypole1360 6]

I have been avoiding putting the 99 in the 206 gti because of the cost . I have just put a second consecutive tank in and am pretty pleased that after 250 miles, the range was still reading 70 miles. Normally the fuel light is on at 250 miles.

 

On top of that, the engine is running great with soooooo much more power , I am sort of gutted that it is a bit wasted on my wife who potters to work and back in it whilst I negotiate the town in an auto diesel Passat.

 

Does it have the same effect on the 205?

 

Calvin

[welshpug 1,657]

only if you alter the ignition timing to suit.

[MiniGibbo 142]

I'd never run it in a car unless it's mapped for 98..

 

Pointless, anyone who argues is simple deluded.

[allye 530 3 Cars]

I'd never run it in a car unless it's mapped for 98..

 

Pointless, anyone who argues is simple deluded.

 

Not quite a cut and dry as that though, don't new cars actually change about ignition and all that depending on what fuel it is using?

[d7ve_b 44 1 Cars]

 

Not quite a cut and dry as that though, don't new cars actually change about ignition and all that depending on what fuel it is using?

 

Yes, modern engines designed or after-market mapped for above 95ron fuel will retard ignition timing for lower octane fuel, I can see this if I log my Audi on different fuels.

[welshpug 1,657]

even older stuff from the early 90's will self learn as they do have knock sensors, but most will need a re-set as they wont sense the fuel, only bring the ignition back and hold it.

[Hheppy 9 1 Cars]

I have heard that the higher octane fuel is better than standard unleaded if you have the car stored for a while, is that true or another urban myth?

 

something to do with a lower ethanol content?

 

cheers

[MiniGibbo 142]

I ran super diesel for a couple of tanks in my t5.. No extra miles, no stick me in the seat speed.

 

Not for me..

[Ryan 99]

I have heard that the higher octane fuel is better than standard unleaded if you have the car stored for a while, is that true or another urban myth?

 

something to do with a lower ethanol content?

 

cheers

 

That's backwards. Higher octane fuel usually has more ethanol.

[welshpug 1,657]

I ran super diesel for a couple of tanks in my t5.. No extra miles, no stick me in the seat speed.

 

Not for me..

 

 

we're not talking about diesel here.

[jackherer 543]

The higher octane is achieved with additives that are volatile so if you leave super in your tank for long enough it'll revert to normal unleaded.

[Batfink 201]

I ran super diesel for a couple of tanks in my t5.. No extra miles, no stick me in the seat speed.

 

Not for me..

 

My BMW 325 loved the stuff. Was not quite enough increase in MPG to warrant the extremely high cost though. That was Shell though - not tried others.

[johniban 59 1 Cars]

its usually used for engines with higher compression, ron as far as i know is todo with the burning rate of the fuel, in other words if you have a high compression engine you want a higher ron so the fuel doesn't ignite before the piston has reached tdc otherwise it will be trying to push the piston back down when its still trying to come up..

 

Correct me if im wrong but thats what i always thought.

 

as for cars learning what fuel is in the car, ive never heard that, i know injectors are always learning on newer cars thats why you get the little injector knock somethimes on start up and pulling away quickly, and on the diesel new cars they used to smoke a little when the injectors were learning.

i know that the citroen ds3 never learnt what fuel it had as it would bring the engine light on if you used under 98 ron and put random missfire fault codes in

[welshpug 1,657]

injectors don't learn anything, they are but a simple valve to let fuel into the engine, the ecu does the learning, using a thing called a knock sensor.

[johniban 59 1 Cars]

you are correct, the injectors dont 'learn' anything but they are 'learnt' (if thats a word? :s ) by means of the engine control unit and as you say the knock sensor

[Simes 248 2 Cars]

I haven't used 98 since my 8v. The almost standard mi-16 (with knock sensor) didn't run as well.

[jackherer 543]

you are correct, the injectors dont 'learn' anything but they are 'learnt' (if thats a word? :s ) by means of the engine control unit and as you say the knock sensor

When the knock sensor detects pre-ignition the ECU retards the ignition timing until there is no more knocking, this will indirectly affect the fuelling but the ECU doesn't alter fuelling in response to knocking. This is the same effect as manually retarding the ignition timing on an 8v by rotating the distributor to adjust for different octane fuel.

 

Edit: I think the word you are looking for is 'taught'

[johniban 59 1 Cars]

im only going on what i was taught,

[ScoobyJawa 23]

Our new (to us) mk5 gti specifies it on the fuel cap, but will run lower octane with reduced power.

 

One things for sure, it's cheaper to fill up and does more miles than our old 1.8T Cupra.

[petert 586]

Just work out the mileage as cents/km. That's the only way to compare fuels. It cuts straight through pub talk.

 

My first Mi16 (DFW) used 10km/L on 91 and 11.5km/L on 98. At the time, fuel was 75c/L for 91 and 80c/L for 98. Which would you use?

[jackherer 543]

I like the way you've converted that to distance/volume just because we're used to quoting it the wrong way round in the UK

[GLPoomobile 958]

Just work out the mileage as cents/km. That's the only way to compare fuels. It cuts straight through pub talk.

 

My first Mi16 (DFW) used 10km/L on 91 and 11.5km/L on 98. At the time, fuel was 75c/L for 91 and 80c/L for 98. Which would you use?

 

I agree. If you are using higher octane fuel for the better economy then you really need to do the maths and see if it's any cheaper in reality. If you have to use higher octane, or choose to for performance reasons then that's a different matter.

 

I've just put my first ever tank full of Shell V-Power in my Volvo as that lot on VPCUK always go on about how much better it is. I'd already done the maths and figured I'd need to be getting a good 3+ mpg more on average for my type of driving. Am I seeing any improvement? Not yet, but it's early days, and to be fair I'd need to run a few tank fulls as it'll be diluted by normal UL at the moment. Psychologically I can't live with the pain at every fill up of paying 10p per litre more for Vpower than normal supermarket UL so I don't think I'll be using it for long.

[petert 586]

I like the way you've converted that to distance/volume just because we're used to quoting it the wrong way round in the UK

 

I've always struggled with L/100Km and when working with cents/Km, it's much easier.

 

ie

.......10km/L on 91 and 11.5km/L on 98. At the time, fuel was 75c/L for 91 and 80c/L for 98.

 

75/10 = 7.5 cents/Km

80/11.5 = 6.95 cents/Km

[Sandy 191]

You claw a little back if you have a Shell card, they give double points on V-power and you can claim it in fuel vouchers. It's still debatable if it's worth it, but my 330 definitely tinkles less and feels crisper on V-Power. We find that's the best fuel in almost all cases on the engine dyno too, race fuels only really temper the behaviour of edgy overly high CR engines; or a little power through the dodgy low down areas where dynamic compression is a problem. Over the top, V-power always seems better.