Pelican Parts: 914 Fuel Octane?

Question: I realize that the car is 23 years old, and manufactured when fuel standards were very different from today. What type of gas should I burn in my car today?

Answer:
     When the 914 was originally manufactured, the gasoline was leaded in order to allow for additional engine and valve lubrication. Today's gasoline, in particular the California reformulated gasoline, is generally harder on today's cars. As a rule, in any older car, you should run the highest octane fuel available at the pump. This is because the car will run cooler, and the engine will undoubtedly last longer. The later cars (75 & 76) were tuned to run hotter and release less emissions. As a result, the engines generally did not last as long. Running higher octane fuel in the car could increase the life of your engine.
     The early cars (70-71) were rated to run at 98 octane with leaded fuel. Later cars were rated to run at 91 octane. These are the numbers from available literature.
     The higher octane gasoline you use, the slower the fuel will burn, and the cooler your car will run. The increased octane represents a fuel that has already been 'burned' slightly, and thus will ignite with less speed. The quick ignition of the fuel leads to a hotter engine and less life out of your heads.

Dave Darling adds:
"I would like to point out one omission. You mention that the octane ratings for the early cars are 98, and for the later cars are 91. What you omit is that these are in ROZ or RON, Research Octane Number. Most fuel pumps that I've seen (that would be only in the US, and mostly in California) are labeled in an average between RON and MON (Motor Octane Number, a different test). The CA stickers outright say "(R+M)/2". There is, as a rule of thumb, around 8-10 points difference between the two ratings for the same gasoline--MON is almost always 8-10 points lower. Therefore, 91 RON octane is roughly equal to 87 pump octane. This, happily enough, is plain old regular unleaded gasoline, at least where I live. For the early cars (original Sixes and all 1.7s except 73 California emissions models), the 98 RON works out to 93-94 pump octane. That would be the Super-grade gasoline, and you might have to look for a little while to find one rated that high.

You also don't address the issue of leaded vs. unleaded fuels, which is implied in the question. The answer is that unleaded fuels are fine. It is only in the very oldest of VWs and Porsches that there were ever any worries about not having leaded fuel. The 914 is simply not that old. The problems with modern fuels and 914s appear to have more to do with some of the additives now in common use--particularly Methanol and MTBE. And the best way to deal with those are to regularly change out your rubber fuel system parts, every year or two."

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Pelican Parts: 914 Questions & Answers...