Petroleum 101

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Stuart
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Petroleum 101

Post by Stuart »

Okay, so I'm just going to put my noobishness on display for the world to see here, but none of the regulars will be really surprised anyway.

Someone please explain to me the difference between 93 and 95 unleaded petrol. How do you decide which one you should use? Does it really make a difference?

I mean, I just stopped to fill up the H1 and they asked 93 or 95 and I had to act all intelligent and given answer. (I asked for 95 in the end, but without any compelling reason to do so.)

I'm not any smarter than a fifth grader, so let's keep thing lower grade here, shall we?
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Re: Petroleum 101

Post by Stuart »

*awaits the obligatory flood of Wikipedia links that I could have just turned to myself anyway*
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Re: Petroleum 101

Post by CapNemo »

It has to do with the compression ration at which the petrol auto ignites and as far as I know it doesn't really make a difference here at altitude so buy the cheaper one down by the beach it is apparently better to buy the 95 one. How ever that is the theoretical answer so I'll bet someone will enlighten us with empirical results soon enough
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Re: Petroleum 101

Post by capanno »

The simplest explanation is that its a different octane level, meaning 95 packs more punch per spoon full. Im not sure if the higher power increases efficiency though. In everyday cars the difference will be minimal, but when it comes to serious performance cars you could gain a small herd of horses, or lose them, depending on the octane level.
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Re: Petroleum 101

Post by CapNemo »

It's not a measure of energy it is the percentage of the pressure where it ignites compared to the pressure where octane ignites
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Re: Petroleum 101

Post by capanno »

I stand corrected then :P
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Re: Petroleum 101

Post by CapNemo »

:lol: well you can design the engines for higher compression ratios that make them more efficient soooo....
That is about as far as my memory go on the thermos for those processes
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Re: Petroleum 101

Post by Stuart »

So in a transport vehicle like an H1 it really doesn't matter which one we use?

Good enough for me. Thanks.
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Re: Petroleum 101

Post by Ron2K »

Besides, we only have 95 down at the coast - it's all you inland people that try to make life complicated. ;)
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Re: Petroleum 101

Post by Stuart »

Capetonians use 95? See, now that makes me think that 93 is better.
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Re: Petroleum 101

Post by senile »

I get 30 km more per tank on 93 than on a tank of 95. No prize for guessing which one I fill up with more often then
Stuart wrote:So in a transport vehicle like an H1 it really doesn't matter which one we use?

Good enough for me. Thanks.
Hummer H1? Would make a difference of 2l/km vs 2,2l/km I guess :D
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Re: Petroleum 101

Post by garp »

Well up in the highveld here I used to use 95 in my lil 1.3 Bantam... Maybe it was in my head but 95 gave it slightly better performance than 93, which on the 1.3 you needed all you could get!
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Re: Petroleum 101

Post by Tribble »

I am with garp - I have tried both and recorded the results. I get between 50 and 80 extra kms if I use 95. (On average tank needs filling at 570kms with 93 and 650 with 95) It could be that I have a French car and it is designed for it.
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Re: Petroleum 101

Post by RuadRauFlessa »

Ok the 95/93 does refer to the octane level which brings us to this link

Please direct your attention towards the below quote from Wiki.
Higher octane ratings correlate to higher activation energies: This being the amount of applied energy required to initiate combustion. Since higher octane fuels have higher activation energy requirements, it is less likely that a given compression will cause uncontrolled ignition, otherwise known as autoignition or detonation.
So one can with certain accuracy say that with a higher octane a couple of things will happen.

1) Better fuel consumption. Less fuel wasted is more fuel in the tank.

2) Increased performance.

3) Longer life to an engine. Autoignition is also causes an effect known as pinging. Due to the fuel igniting the oil on the inside of the barrel is burned away and then causes extra friction and heat when the piston does have to travel. This causes extra strain on the connecting rods and the crank shaft (which in turn also lowers performance).

It is worth noting that even in vehicles considered as low performance the difference between 93 and 95 will be noted. Better fuel economy and increased performance.

Personally I fill up with 95 at least once out of the four times I fill up in a month. I Never ever ever ever as in really never let my fuel gauge go into reserve (couple of reasons for a different conversation). I found that this is about the optimum for my little 1.4l Vivo. One reason why I don't let her fuel tank run empty is worth noting here though, with some left in the tank the 95 and 93 mix and as such you never have a clean mixture of the one or the other in the tank. Trust me it makes a difference. Through a normal week's driving 95 I can get about 70/80km more before I fill her up. Much the same as the stats Tribble gets.
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Re: Petroleum 101

Post by SykomantiS »

Well, I'n going with Cap and RRF on this one.
I do have a tiny issue though:
It is worth noting that even in vehicles considered as low performance the difference between 93 and 95 will be noted. Better fuel economy and increased performance.
I'd like proof of this. :| I have on occasion filled up my litrebike with 93 since I had no other option or other garage in range. I've seen ZERO difference- admittedly, I've never tried to find a difference. Also, 95 does NOT give higher performance IF your vehicle can use 93 WITHOUT autoginition/detonation/pinging.

We had a lengthy discussion one day on a breakfast run when a buddy of mine who plays guinea pig for a dyno shop told me his Suzuki puts out higher numbers on 93 octane than on 95. Naturally I called BS. Turns out I was dead wrong. A high performance/high compression motor stands to gain more from 95 if pinging does occur when using 93.

That being said, I agree that if you are unsure, go for 95. Though I honestly don't think you will notice the difference.
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Re: Petroleum 101

Post by RuadRauFlessa »

Well Syko.. agreed that some engines would be more than happy to run on 93. My Vivo's engine has a compression ration of 10.5:1 seeing as I have done the economy test numerous times over a period of 18 months I get a significant difference in fuel economy. I have to note that 10.5 is rather high as compared to most vehicles running at around 9.5. Then again I could also only comment from my experiences and my experience has shown me what I have stated in my previous post.

If Stuart can let us know as to what vehicle he is driving then we might be able to make a more accurate summation as to his individual vehicle's behavior.
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Re: Petroleum 101

Post by RuadRauFlessa »

Oh wait he is referring to the Hyunday H1... quick search indicates from the Hyunday website

2.4 MPI = 10.5
2.5 TCI = 21.0
2.5 CRDI = 17.6

If we follow our train of thought it would stand to reckon that he would in fact get a a benefit from higher octane fuel
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Re: Petroleum 101

Post by SykomantiS »

He said Huyndai H1 iirc.
Also, 10.5:1 is pretty much a standard CR for a car nowadays, cars running 9.5 or lower are generally of the forced induction type- comparing apples and oranges again, my bikes has a CR of 12.5:1 :wink:
So you can guess my surprise when I heard that the K9 Suzuki (with an even higher CR) made better numbers on 93.

I think I will do a little test of my own- I wil in the next 2 to 3 weeks fill up with both and note the difference- I recently started using fuelly to keep track, since I now commmute between joburg and pta daily.

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(I have to note that is equal to a certain other forumite's diesel fiesta) :P
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Re: Petroleum 101

Post by Kennyisalive »

SykomantiS wrote:
(I have to note that is equal to a certain other forumite's diesel fiesta) :P
You Talking about me... :P

Here is my Fuelly Stats... Reminds me I need to Add 1 in...
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Re: Petroleum 101

Post by RuadRauFlessa »

2 to 3 weeks will not give you consistent indications. It could however give you a glimpse. Like I said I have kept records on my 1.4l Vivo for 18 months and the stats all suggest that I get better consumption with 95 compared to 93. On 95 I can basically do one more round trip a week to work. That 80Km odd is not something to shy away from.
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Re: Petroleum 101

Post by SykomantiS »

Agreed, but I'll settle for a glimpse right now. If you get better consumption on a 95 then by all means- that's what it is there for. I'm just saying that this isn't always the case.
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Re: Petroleum 101

Post by RuadRauFlessa »

Agreed it isn't always the case. But the theory and the science would indicate that 95 should be the better option regardless... But then again real world rarely coagulates with theory.
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Re: Petroleum 101

Post by IcePick88 »

Ron2K wrote:Besides, we only have 95 down at the coast - it's all you inland people that try to make life complicated. ;)
:lol: :lol:

Yeah the valies really complicate things. I guess it's all that insufficient oxygen in the atmosphere there at altitude. :lol: :lol:
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Re: Petroleum 101

Post by Stuart »

senile wrote: Hummer H1? Would make a difference of 2l/km vs 2,2l/km I guess :D
:lol:

Yes, the Hummer is my economic vehicle. I use the Lear Jet when I'm not concerned with economy.

No, that would be a Hyundai H1 (kombi-type vehicle).
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Re: Petroleum 101

Post by WiK1d »

You all are yammering on about 93 vs. 95 when Stuart didn't even use the correct term. Petroleum != Petrol
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