odurandina

the money saved goes in a tin can labeled table dance.




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Fintro11

91 octane

UltimatE157

Yup, two main rating systems (MON and RON) ... and the US/Canada and a few other countries use the AKI or sometimes called PON system. AKI = (MON + RON)/2. Now you can see why octane ratings can become confusing quick.

This is why you can have one car running 3 different octane ratings, and they will all be the same Octane, just different scale. Same thing as saying 32*F = 0*C.

My 87 N/A says AKI rating of 86 minimum under gas lid. Therefore 87 Octane (in the USA) is just fine to use.

ETA: Sweet jesus that picture above. Drool.

Jrboulder

I used 85 in the summer and 87 in the winter in my N/A. In Colorado summers you can get a density altitude of 8000+ so there is really no point in running 87 unless it knocks, which it never did for me.

TexasRider

I just go with the premium. Not for the 006/1,000,000 parts iso-octane, but for the additive packages that are in the companies premium blends.

The additives are expensive of course, but I believe there is a higher level of quality control during the blending. While I am an oil and gas engineer, I am not a refining engineer , nor to I pretend to be. But I have distilled this down so to say from buddies of mine who are in refining and formulating.

The addition of ethanol only increases my idea of the additives, although ethanol is one of the additives of course, and does add to the anti knock properties of the gas.

Many of the "base" gas is the same - or can be different. Shell can have Conoco base gas. Chevron may have Shell. They just swap and sell it to each other based on demand and logistics. What makes the gas different is additive packages.

What you can do , if you want to really get the best from the gasolines and additives is to switch around to get the best from the respective deposit removal additives. I for instance use Shell and Chevron. Maybe a few months with one then the other.

And older engines might need a bit more octane too - especially when they are under higher loads - like a 951 might be at times.

TexasRider

I dont see any table?

Fara

I think it would be wise to point out I'm in Au, so I've got a Euro engine in my '83.
It's got a higher compression rating and recommends 95Ron. I run 98 as the fuel is cleaner in general and the seat of my pants dyno seems to suggest more torque at lower RPM's.

sweetskillsrk

For the four years of owning my 944 I've used premium every time I fill up. I only used midgrade one time and my DME went kaput while still on that tank of gas, obviously it's completely unrelated, but I've always used premium. Now that gas, especially premium is getting so freakin expensive, I've contemplated just straight going regular, but never actually done it. My 44 gets pretty crappy gas mileage, about 22mpg my last informal calculation, so buying premium sucks. My 44 currently needs a new head gasket but she's my daily driver so there's no way I can down her long enough to fix it. Would running a lower grade fuel have any effect on the worsening head gasket? (Right now it's only a small leak so I just change my oil every two months or so to keep the coolant out of the oil).

bordin34

On the sticker it says 91 RON which equals 87 AKI or US octane rating.

Butters944

Oh! Thanks bordin.

I normally get 22 city mpg, and up to 30 highway...

pcarfan944

Premium.

I tried 87 oct once and the car didn't idle nearly as smooth, and it lacked noticeable pull throughout the rev band.

VirginiaF1

Shell V-power with Nitrogen 93 only... it is a "TopTier" gas. I also now use Shell's Rotella.
www.toptiergas.com

With the 10.2:1 Compression bump of the '88 MY, I clearly find an improvement in power, mileage and idling with 93 vs 87 or even a mid-grade (89 or 91).

My 240,000 mile original engine probably has an even higher compression bump with the volume-robbing carbon within the CC... and as 93 AKI burns both cooler and more thouroughly than lower AKI rating gas I find the added expense well worth the investment.

PS: My owner's manual calls for at least 90 AKI (U.S. Rating System)

River

Interesting. I have an 88 too.

I've run premium and regular. Didn't really notice any difference (power and mileage). Idles perfectly, averaged 18 mpg on a trip with my foot in it the whole time (380 mile trip). And this was before rebuilding my injectors.

Na=regular
turbo/s/s2=premium

although, I might try a tank maybe with the injectors. And mine is an automatic too and get that mileage.

83 944

i use what octane gas to the compression ratio like you should. simple as that. under 9.5:1 87 to 89 is fine on most engines.

V2Rocket

whatever 87 octane is cheapest...E85 soon.