What is the maximum safe octane rating to use in pre-war cars?

[Stude Light]

14 minutes ago, jp1gt said:

has anyone had problems with the alcohol eating up the carburetors?  I use aviation fuel for my small engines. High octane and no alcohol.

The biggest issue with ethanol is that it will attack elastomers that were not designed with ethanol in mind. So, fuel lines, “rubber” fuel pump diaphragms and seals, shellac coated cork floats all used before the introduction of ethanol will gradually fail unless they are upgraded to ethanol compatible materials. Ethanol may also tend to oxidize some metals, especially when there is some water in the fuel which ethanol will hold in solution.

 

Although a bit too high an octane I use AvGas in any equipment that sits for a while as it has at least a 7 year life and never varnishes.

[jp1gt]

The experience that I have had with ethanol is when you open the carb up it is full of white powdery stuff that blocks off the passages. Anybody have this problem with an old car?

[Marty Roth]

The Octane rating we see on a pump :

The octane number is actually the simple average of two different octane rating methods—

motor octane rating (MOR) and research octane rating (RON).

 

How do these numbers relate to the Octane numbers we saw in the 1950s / 1960s, etc?

[ply33]

6 minutes ago, Marty Roth said:

The Octane rating we see on a pump :

The octane number is actually the simple average of two different octane rating methods—

motor octane rating (MOR) and research octane rating (RON).

 

How do these numbers relate to the Octane numbers we saw in the 1950s / 1960s, etc?

Not sure when they standardized but I think the usual number posted in the old days was the research octane number as it was higher so it sounded more impressive in the gasoline company advertising.

[Marty Roth]

1 hour ago, ply33 said:

Not sure when they standardized but I think the usual number posted in the old days was the research octane number as it was higher so it sounded more impressive in the gasoline company advertising.

@ply33,

 

Thanks. That is what I assumed as well. I believe the current numbers displayed on the pump is the average of the Motor and the Research Octane Ratings,

as in (MOTOR + RESEARCH), that total divided by 2