V2Rocket

Yep, taped the labels when got my car painted in 2011. Not the best tape, but whatever.

My car is a very late 85/1, with some of the 85/2 features already installed. Don't know what HG came off when I rebuilt the engine, but the one that went back on was the standard kit with the "turbo" HG. Head got shaved .015 or so IIRC too, never had a problem on 87 octane, ever. Pistons were standard 9.5:1 units.

Car was originally bought in CA, it lived in TX for a while and then came back to CA where I bought it in 2005. Could very well be that somebody in Neckarsulm threw on a 924 gas sticker by accident, but again, I've never had any knocking or fuel issues, and my car pulls better than any other NA I've ever come across, "confirmed" over the course of several stop lights

Extra power from running on the ragged edge of detonation, I reckon

16valver

Don't forget that RON doesn't mean octane in the US. You have to do some math to get things from Euro measurements to US measurements. RON = research octane number, MON = motor octane number. AKI = anti knock index which is the numbers you see on pumps in the US.

As Rocket's sticker states, AKI is an average of RON and MON numbers. Basically RON and MON have something to do with burnability and behavior under load (hence the average).

Just food for thought incase anyone overlooked that.

use2windsurf

I dont have a sticker on my fuel cap any more, but the users guide for the 87 NA calls for a minimum of 91 RON which is the same as 87 octane (AKI) as sold in the US. So all indications are that the 87 octane should be fine.

1987 Red 944 N/A *** NOTE- I probably posted from my iPad, please excuse any typos, bad punctuation or odd grammar, if it is unreadable, it probably was posted from my iPhone.

PerceptionProblem

Sorry for missing most of this convo, I was dealing with some balance shaft woes. (All is right and good in the world now:-) )

I use 87. I steer clear of Arco and Valero as their gas seems crappy in my daily, so I'm not gonna put it in my p-car.

That being said, every few months I'll run some 91 chevron premium. Maybe it's foolish to really believe that they have additives that help clean valves etc, but it's never done me wrong.

ZR8ED

I checked a friends Canadian owners manual (I don't have one) and it specified 87 octane for my 86 8 valve non turbo.

John_AZ

I agree with V2Rocket/Spencer on use of only "regular" gas in base 150HP 944/924S cars.

I have never had any problems in the 150HP '87 924S with regular gas.
Fuel door Min Octan 86:


The '88 924S 160HP fuel door does say Min Octan 91


J_AZ

konakat

91 RON corresponds to 86-87 octane with the US (R+M)/2 octane rating. RON is used in Europe.

Van

I'm amazed at this variation.

Here are the fuel door for my '84 chumpcar, '86 race car, and an '87 924S.

V2Rocket

But as was said before, 91 RON = ~87 on the US gas octane scale.

944Ross

From the '86 Owner's Manual. I've never run anything but Regular, no issues.

curtisr

That's nothin'! You should smell your pee after eating a pound or two of asparagus!!! Wait...am I off topic here? Sorry 'bout that...

dave1192

There is confusion between RON ratings and US CLC/AKI Octane ratings. This is from the 86 944 NA owners manual:

944: Minimum octane rating is 91 RON (87 CLC or AKI rating on US fuel pumps).
944 S / 944 Turbo: Minimum octane rating is 95 RON (90 CLC or AKI rating on US fuel pumps).

I've never put anything but US Octane 87 in my 86 NA and found no problems using this fuel.

william_b_noble

if you actually want to understand octane ratings, the SAE automotive handbook has an excellent few pages explaining it and how it is measured. you may also wish to refer to this http://www.astm.org/Standards/D2699.htm

Significance and Use



5.1 Research O.N. correlates with commercial automotive spark-ignition engine antiknock performance under mild conditions of operation.


5.2 Research O.N. is used by engine manufacturers, petroleum refiners and marketers, and in commerce as a primary specification measurement related to the matching of fuels and engines.


5.2.1 Empirical correlations that permit calculation of automotive antiknock performance are based on the general equation:

Equation D2699-13A_1


Values of k1, k2, and k3 vary with vehicles and vehicle populations and are based on road-O.N. determinations.


5.2.2 Research O.N., in conjunction with Motor O.N., defines the antiknock index of automotive spark-ignition engine fuels, in accordance with Specification D4814. The antiknock index of a fuel approximates the Road octane ratings for many vehicles, is posted on retail dispensing pumps in the U.S., and is referred to in vehicle manuals.

Equation D2699-13A_2


This is more commonly presented as:

Equation D2699-13A_3



5.2.3 Research O.N. is also used either alone or in conjunction with other factors to define the Road O.N. capabilities of spark-ignition engine fuels for vehicles operating in areas of the world other than the United States.


5.3 Research O.N. is used for measuring the antiknock performance of spark-ignition engine fuels that contain oxygenates.


5.4 Research O.N. is important in relation to the specifications for spark-ignition engine fuels used in stationary and other nonautomotive engine applications.



1. Scope



1.1 This laboratory test method covers the quantitative determination of the knock rating of liquid spark-ignition engine fuel in terms of Research O.N., including fuels that contain up to 25 % v/v of ethanol. However, this test method may not be applicable to fuel and fuel components that are primarily oxygenates.2 The sample fuel is tested using a standardized single cylinder, four-stroke cycle, variable compression ratio, carbureted, CFR engine run in accordance with a defined set of operating conditions. The O.N. scale is defined by the volumetric composition of PRF blends. The sample fuel knock intensity is compared to that of one or more PRF blends. The O.N. of the PRF blend that matches the K.I. of the sample fuel establishes the Research O.N.


1.2 The O.N. scale covers the range from 0 to 120 octane number but this test method has a working range from 40 to 120 Research O.N. Typical commercial fuels produced for spark-ignition engines rate in the 88 to 101 Research O.N. range. Testing of gasoline blend stocks or other process stream materials can produce ratings at various levels throughout the Research O.N. range.


1.3 The values of operating conditions are stated in SI units and are considered standard. The values in parentheses are the historical inch-pound units. The standardized CFR engine measurements continue to be in inch-pound units only because of the extensive and expensive tooling that has been created for this equipment.


1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific warning statements, see Section 8, 13.4.1, 14.5.1, 15.6.1, Annex A1, A2.2.3.1, A2.2.3.3 (6) and (9), A2.3.5, X3.3.7, X4.2.3.1, X4.3.4.1, X4.3.9.3, X4.3.11.4, and X4.5.1.8.



2. Referenced Documents (purchase separately)

ASTM Standards

D1193 Specification for Reagent Water

D2268 Test Method for Analysis of High-Purity n-Heptane and Isooctane by Capillary Gas Chromatography

D2360 Test Method for Trace Impurities in Monocyclic Aromatic Hydrocarbons by Gas Chromatography

D2700 Test Method for Motor Octane Number of Spark-Ignition Engine Fuel

D2885 Test Method for Determination of Octane Number of Spark-Ignition Engine Fuels by On-Line Direct Comparison Technique

D3703 Test Method for Hydroperoxide Number of Aviation Turbine Fuels, Gasoline and Diesel Fuels

D4057 Practice for Manual Sampling of Petroleum and Petroleum Products

D4175 Terminology Relating to Petroleum, Petroleum Products, and Lubricants

D4177 Practice for Automatic Sampling of Petroleum and Petroleum Products

D4814 Specification for Automotive Spark-Ignition Engine Fuel

D5842 Practice for Sampling and Handling of Fuels for Volatility Measurement

D6304 Test Method for Determination of Water in Petroleum Products, Lubricating Oils, and Additives by Coulometric Karl Fischer Titration

E344 Terminology Relating to Thermometry and Hydrometry

E456 Terminology Relating to Quality and Statistics

E542 Practice for Calibration of Laboratory Volumetric Apparatus

E1064 Test Method for Water in Organic Liquids by Coulometric Karl Fischer Titration

ANSI Standard
C-39.1 Requirements for Electrical Analog Indicating Instruments

John_AZ

This is a lot of technical/research info to say ....
"most commercial blends of gas have a typical O.N.-Octane Number between 88 and 101."
See reference Scope ---1.2

J_AZ

Van

So, filling up today, it looks like my part of the US does use the same octane rating system...