Gas/Petrol Octane
 

Just an observation, but looking through posts on here it looks like a lot of you US guys are stuck with 91 and 93 RON unleaded.

Totally bizarre. Over here in the UK basic bargain supermarket petrol from the likes of Tesco's or Asda(Walmart) is 95 RON.

BP Ultimate 97 is what I've settled on as it's easily available locally.

Tesco's do "Tesco 99" and Shell do V-Power Nitro 99. I'm not sure I would trust Tesco 99 and there are no shell stations in my area.

BP also do Ultimate 102, but I haven't seen it yet.

The petrol filler has a sticker on it in the UK says something like "98 RON Unleaded only!"

I understand the engine will adjust the timing of course, but with higher octane fuel you apparently get more ignition advance and slightly more power and/or better economy.

Downside, of course, is over here BP Ultimate 97 costs $2.34 a litre, crica $8.86 a US gallon. An average fill up costs me about $90-100.

I hear 93 octane is readily available in the eastern parts of the US but out here in California I never see anything higher than 91 :cry:

All true. 91 octane is the highest around here, and according to pure-gas.org there are 14 ethanol-free stations in the entire state (38 million people)

I fixed that problem by running E85. Now my bone-stock twin feels like it has S2000-levels or pull towards redline, except with a less peaky powerband.

US Octane is in AKI units
 

In the US, the octane rating is listed in AKI units whereas in the UK it in in RON units. They differ by about 4 to 5 points according to Wikipedia. So an octane of 93 in the US is basically 97-98 RON.

In my area you could get 93octane for $4 us gal, there isn't E85 at least that I know, but I found in the commute to work Sunoco 100 at the pump and yes sir! The car will run better, don't know if could track down the s2000 with the gas only, but if you have mods (FI) and retune expect from 30 to 50 whp more that whatever was the base.
Ej. SC kit could get you to 250 whp, with the gas and tune maybe you could hit the 300 whp. At $10.50 us gal

I an 93 nonethanol until I moved now I run 92 nonethanol

No, our gas is rated in AKI.

http://en.wikipedia.org/wiki/Octane_...ndex_.28AKI.29

Ah, that makes more sense.

just a random thought, Does weather affect the fuel. I mean in US mostly California, we have warm weather through out the year. I think that might help fuel to ignite or evaporate better than in cold weather!

Cold air is more dense and contains more O2. (think intercooler) I think slightly damp air is even better.

In Ireland I swear you notice it on cold mornings.

Warm climates may encourage evaporation of the more volatile compounds, but surely for hot countries they have additives for that or fuel would have a much shorter shelf life or need to be stored in unvented tanks.

Here in France we get either 98 RON, 95 RON or 95E10 RON 10% Ethanol.

I've tested 95E10 and 98 and both seem to work the same....

Correct!

Actually, cold temps increase performance, but warm weather increases MPG.

Weather doesn't really effect "fuel", but it does effect the density of the A/F charge. Cold air is more dense, so lower ambient temps actually increases the amount of A/F into the engine. And you not only get a bigger A/F charge, yoou get an increase in the effective CR...its like free FI.

You get more fuel if you fill on a cold day.

That's a myth. Fuel of course is stored in underground tanks, and the tank temps are essentially constant.

" Filling Up When It's Cold Outside

Get your gas in the evening or early morning - the fuel is cold, and therefore denser. The truth about this myth is that you can barely register a temperature difference, since gas is stored in cool underground tanks, so fill up when you want. There are no savings to be had by waiting until it's cool out."

http://www.investopedia.com/financia...ally-work.aspx

Where I used to live in California we had VP Racing and they had 95 AKI and 102 AKI fuels on separate pumps. 95 was $4.99 and 102 was pushing $8/gal I believe...That was 2008 when I last paid attention to that stuff though, when I had my S/C'd GTO (Vauxhall Monaro for you Brits :) ).

I should have added a smiley. It was part "tongue in cheek".

We are talking about few cubic inches a gallon for 20F degree shift.

Winter and summer, you might be able to measure it in some regions, but it's not going to make an impact on your fuel bill unless you can buy your summer fuel in winter and store it.

The gas industry apparently defines a gallon, a gallon at 60F.

In aviation when filling an airliner, you get your fuel in Kilos or Lbs because that matters and makes load sheets easy. Instruments are usually in Lbs per hour or Kilo per hour, because weight matters more than how full the wings are. However, the density and temperature of the fuel are noted when ordering and if beyond limits the fuel load adjusted. The fuel may get pretty damn cold at 40,000ft.

Do warm climate areas (Cali and FL) switch to the winter blend fuels? Just curious.

I just paid $3.55 a gallon for 93 octane (Pilot) here in Virginia. Shell is always about $.10 to $.20 more a gallon than most of the others so Shell is $3.75 now for 93 octane.

Yes we do.

Right now 91 oct is $4.39/gallon @ my local shell station.