is it worth using 95 octane?

[gnutz2]

It totally depends on your setup.

ECU, turbo, intercooler, compression ratio?

I would not dream of using it on my 500+hp setup but a standard car on motronic would be fine.

[A80Avant]

setup is not relevant if you can tune the car on all aspects.

of course, you will ask why build a 500hp setup and only run 300hp?

well if you have the option and you don race the car, but use it everyday, since you dont have a diesel hangin by, you could.

[LSG]

sure i agree, but with vems i can still run 95 without problems, and if i dont go 2bar all the time, it should still be happy at 1.4

do all of you run your cars full beans everyday?

we build lots of big hp bikes and we use race fuel only but we always tell the lads running smaller hp to run 98 ron.I think you pay your money you no the rest.As to your full beans everday,no i don,t think we do but you,d be so peed of if you wanted to go for it and couldn,t cos of 8p.maybe chop it in for a 16 valve. no hp to get worried aboutSorry to anyone who run a 16v Also it,s only going to get worse

[Billman]

I have switchable maps and the one is low boost-timing for 95! Its cheaper and when I have others im the car with me i don't thrash it anyway. The 350+ hp are more than enough for the motorway at cruising speeds and enough when you must overtake. So you travel cheap but also safe (custom map for cheap fuel).

If I had here E85 I wound do one for gasoline and one for E85.

[johne]

I've done 140K miles on my ABY on 95 RON with no noticable difference except in very hot weather. If you've got over 250hp you're not going to notice 10 less when on 95 in normal driving.

Read what Paul N has written about how Motronics controls boost to maintain output across a wide range of temperatures then at ambients of 10 degress C or so or lower and there's no point in using 98 RON as Motronics is already stopping you from getting the most from your engine.

and the extra mpg from 98 RON doesn't happen so 98 doesn't save you money that way either. I've done back to back checks over several tankfuls to prove it.

John

[A80Avant]

thanks for the answers lads,

it is really interesting getting so many answers that are in favour of the 98 octane fuel and realising that almost everyone is driving their car at full boost most of the times.

i have mapped my car to run 2.1bar and to be honest, i rarely have to use it, as the car is so fast even at 1.4bar. Sure its super exciting when i am going WOT but i dont need to do that cause a 3076 turbo is big enough to thrill you at 1.4 bar anyway.

Since this is not a weekend car for me but an everyday car, i cannot imagine myself going to Morrisons for shopping using handbrake turns(which doesnt work on the rs2 anyway) and being at full boost for the full 2.5miles i have to drive to, although its a 2 lane road to there.

I have done about 100K kms in 2.5 years mostly on trips around the UK and europe and i am trying to realise that when im on cruise doing anything from 60 to 90mph, on a full loaded car or just me and my wife, whether it makes a huge difference if i use 98 octane or 95 or even a mix of those 2, since most of the time im in no boost circomstances. Sure on 6th gear if you have to boost the load is higher and if you have a high boost car and low octane fuel you may end up in trouble, but i can compensate for that with lowering the boost and tailing off advance on a safer map, enough to keep giving me some thrill during my trip, be safe and not overdo it.

i recently mapped a friend's rs2 completelly for 95 octane fuel, made it go only up to 1.6bar on a 3071R turbo and fully stock engine and compression (ADU) and i made it extra safe on timing. we didnt hear it knock once on inlet temps of 26-36C and the car accelerated nicely and wasnt at all a slow car.


So i may need to rephrase the question a bit and say: if you were using the car everyday and had no replacement, + had the option to use a fast and a slower map version, would you use the lower octane fuel to save some money? OR do you think that the amount saved ie in a year is not worth the hassle?

as i said, if you like to put the best fuel in your car,and choose something like BP/Total/etc, then the price difference is 118.7 for unleaded and 139.9 for S unleaded from my usual BP station i use. So thats not 8p!!! that is a total of 21+ p per litre!!!



and dont tell me that you are using morrisons/tescos or asda's 98 octane rating fuel and you are doing the right thing as well, cause i do have my doubts about 98 fuel costing only 1.21 p litre and actually being proper 98 octane. I would certainly NOT use that fuel on my high powered map...

[newsh]

You will actualy make slightly more power (or more milage) on 95 than on 99 up to the point when it knocks. If you're driving on part throttle on the motorway and not going WOT then 95 makes loads of sense.

If you think about it it makes sense, the anti knock additives are there to slow the burn down, if its harder to burn the fuel then you get slightly less energy but the higher octane allows you to run more advance which is more efficient. Motronic can't measure the octane on 95 it just gives you the best timing it can till you get knock and then it will pull back.

[s2driveruk]

odd, when Ciaran and I were driving round europe in the summer, we filled up with some German 100Ron and the cars cruised for miles more than on standard 95 or 98 and I mean well in excess of the normal range. and to clarify we were not sticking to a Uk speed limit either Therefore I'd originally concluded that the higher wuality the fuel, the better burn and the less fuel was required for it.

[EspenW]

Still no E85 available in the UK? Cost here is approx. 0.80 a litre. You need approx 30% more, so that equals approx 1.04 a litre.
115+ octane and gives 5-20% more power/torque at the same boost/timing (more when tuned).

[A80Avant]

this is true, that with 95 you do get less miles to the gallon, i just need to see how much less.

also the other thing to test would be to see if those cheap 98 oct. are worth it as well.

im not aware of any 100oct rating though. all around europe i see 98 octane, and those adv, as 100 are actually 98.

anything above 100 is either race or E85

[A80Avant]

unfortunatelly not where im at Espen. I would try it out if it was more readily available, and it would be worth using the second config in vems

[newsh]

If you can get high octane with good burn speed then you will have the best of both worlds, at that point you may get more milage, lower octane usually has a higher burn speed but this possibly depends on the brand.. Its not just a question of octane

Here is an interesting article by Marc at Factory Pro. http://www.factorypro.com/tech/tech_..._vs_power.html

[Billman]

in Greece we have 99+ or BP-100 but if they are better than 98 is not known.

No E85 over here either!

[A80Avant]

they are all 98 Bill. just advertising that calls them 100

[Billman]

actually not as has test in magazines prove that cars with 200-300 hp seem to make repitedly 3-5 hp more on them than on the "normal" 98 but the question remails is the combustion difference (are they more safe?) so big? Do 2-3 RON number make such difference.