[Kodak]

Can you really feel any difference in power between a 91 octane or 93 octane ?

[ik999]

I can't feel any difference in power between shell91 and sunoco94

but shell91 somehow runs smoother?

I don't know

[phozenstone]

i can't feel any difference, i don't even look to see what octane it is anymore, i just pick whatevers most expensive. Some gas stations have 91 as "supreme" while others have 93

[Kodak]

Originally Posted by phozenstone

i can't feel any difference, i don't even look to see what octane it is anymore, i just pick whatevers most expensive. Some gas stations have 91 as "supreme" while others have 93

I used to just use the 93 octane until i read in the manual that for a 2006 325xi that the recommended octane is 91 octane, so I've been using Sunoco 91 octane ever since, especially since the 'gas crisis' .

[purplewidow]

93 is better 91 is just the minimum. you will get more power out of these cars with higher octane maybe not a 1980's station wagon but a modern bmw for sure.. more octane means more power and cleaner burning. 110oct has to be kept in a static free drum it is so flammable..if you leave the top off it will evaporate super fast.

[rob2010]

u prob wont feel much of a difference in terms of power but you should be able to get more millage per tank.

[camaross305]

you wont feel much more power maybe 3-4hp (which you wont feel) from 91 to 93. Now once you turn up the boost with a tuner thats when 93 yields more power

[ska325xi]

the difference I can feel is the $0.30 I save every gallon

[BavarianBullet]

IMO you probably won't feel any seat of the pants difference and even a dyno would barely show a power difference between 91 and 93 octane.

What I can tell you from racing a lot on pump gas years ago (with 5.0 mustangs) was that there are differences between various fuels at the same octane rating.

How I know this is from experience is this: Back in the 90s mustangs were the first model of sports car to go fast in large numbers and they had no timing retard knock sensors. One of the key tricks to make them faster near stock was to swing the timing (by moving the distributor a few degrees) from 10 degrees to about 14-18' before TDC.

This invariably lead to audible detonation as people would try to make their cars as fast as possible for less $.

One things we learned pretty quickly was that certain fuels behaved better and had much less audible pinging or knocking than others. Shell was complete crap and pinged horribly whereas mobil and amoco tended the opposite and were favored.

It's been 10-15 years since those days and things may have changed but it's a fact that the R/M2 method to derive a published octane number is just an average. It's an average of a fuel's research and motor octane values / 2 and some engines seem to like more of one vs another.

You'll never know what the breakdown is unless you get tech specs of the fuel (from the internet, not likely from the gas station) and test and see which one your engine likes more.

my 2c.

[camaross305]

Im not sure about 15 years ago but now shell actually has really good gas. Ive seen analysis tests showing that chevron and shell on avergae are some of the cleanest fuels.

[Lassaxi]

Originally Posted by ska

the difference I can feel is the $0.30 I save every gallon

+1

[Kodak]

Originally Posted by Lassaxi

+1

You are so right

[jpsimon]

on the dyno you will see pretty decent differences when you're looking at a modded car with 91 vs 93. I'll post up a thread that some of you might not have seen... of the comparison of my car with 93 vs 100 octane.... i think you'll like the results

[AllydNYC]

I put 93 in because it's only like 4 cents more then 91 where I am.

[sapperelite]

I agree with what was said about better mileage from experience. I was driving the car in Spain and went from Madrid down to Cadiz. I filled up with Premuim before I left Madrid and got great mileage down to Cadiz. I filled up in Cadiz with the lower octane premium, don't know what octane because they use a different rating system in Europe, and got horrible mileage. If I remember correctly, I got about 40 miles more off the premium that the lower grade. I also get the highest octane possible in the US because I can hear an audible difference in the engine sound with good vs premium.

[smartys]

Actually I've been wondering about this issue also. I JUST (finally) stepped into my e93 convertible, which I imported from the USA. when I picked up the car, it was filled with a tank of US premium gas, I presume 93. it was a monster, but smooth and silky. I filled up with Canadian 91, and the next morning I noticed the engine was not as smooth, and I actually feel a little less kick to it....still fast, but it seems like there's something missing.......

[exidisjon]

Originally Posted by AllydNYC

I put 93 in because it's only like 4 cents more then 91 where I am.

Same at sunoco. Its only llike 5~10 cent difference and i heard higher octanes are better for the car??
At least feels a bit better putting in better gas.

[Mooreski]

Originally Posted by ska

the difference I can feel is the $0.30 I save every gallon

There's a $0.30 difference between 91 and 93? That's crazy!! What's the diff between 87 and 93?!?!

[ShereKhan]

If there is one thing that made me smile

The fuel maybe cheaper in the US than the UK

But at least we get Ferrai engineered fuel all over the UK

I run mine on Shell V Power 99 Octane and my company pays for it too!

You guys over the pond need to get 99 Octane.....The standard in the UK is 95 Octane minimum

[Lassaxi]

Originally Posted by ShereKhan

If there is one thing that made me smile

The fuel maybe cheaper in the US than the UK

But at least we get Ferrai engineered fuel all over the UK

I run mine on Shell V Power 99 Octane and my company pays for it too!

You guys over the pond need to get 99 Octane.....The standard in the UK is 95 Octane minimum

Haven't we beaten this to death yet? I think most everyone here knows that European 95 octane is RON, and US octane ratings are AKI. Your 99 RON octane is equivalent to our U.S. 94 AKI octane.

Even wikipedia knows this:

"Different countries have some variation in what RON (Research Octane Number) is standard for gasoline, or petrol. In the UK, ordinary regular unleaded petrol is 91 RON (not commonly available), premium unleaded petrol is always 95 RON, and super unleaded is usually 97-98 RON. However both Shell and BP produce fuel at 102 RON for cars with hi-performance engines, and the supermarket chain Tesco began in 2006 to sell super unleaded petrol rated at 99 RON. In the US, octane ratings in unleaded fuels can vary between 86-87 AKI (91-92 RON) for regular, through 89-90 AKI (94-95 RON) for mid-grade (European Premium), up to 90-94 AKI (95-99 RON) for premium (European Super)."