<VV>Octane

[Padgett]

>was the regular gas in 1964 a higher octane than now?

Not necessarily but it is measured differently. There are two different 
measuring schemes: the Motor method which is a lower number but a better 
measure of how an engine behaves under load and the Research method.

Back in the day, the Research number is what was posted on gas pumps since 
it was a higher number and better for advertising. Originally the "66" in 
Philips 66" was the octane number (and good in the 30's).

Once the FEA took over after the first gas crisis, the fed in its infinite 
wisdom decided to change the pump number, not to the Motor number but to 
something called "PON" (Pump Octane Number) which is an average of the 
research and the motor method. *In general* the PON is 4-5 points lower 
than the Research method.

Now in 1966 when the General said "Regular", it meant 94 octane. "Premium" 
was 98 and "Super Premium" as in Sunoco 260 was about 100. Even being 
charitable 94 octane back then translates to 89 PON and a good premium 
today (93) is close to the 98 of premium then.

For GM, 1971 was the year the octane requirement across the board dropped 
to 91 (~87 PON) and is where today's Regular comes from.

So in sooth, an engine designed for Regular in 1966 really needs 89 today 
and not 87 though with retarded timing and richer jets (GM had specs for 
operation in countries with poor gas) it may work.

However, the Corvair (like nearly all GM engines in 1966 since Corvette 
dropped the FI after '65) is really crudely controlled with a distributor 
and carburetors approximately feeding an oversquare engine. Back then, 20 
mpg was "enough" to be an economy car and Premium was just another 20 cents 
per tank.

Today small cars have carefully designed combustion chambers, computer 
feedback control, knock sensors, O2 sensors, and digital ignition & fuel 
injection. This permits an engine a little over half the size of a Corvair 
to produce the same power (actually more since now measured in NET rather 
than SAE gross)  and 10:1 compression on 87 PON.

So back to the original question, does "Regular" in a 66 owner's manual 
mean 87 PON and the answer is No, but 89 is pretty close.

Padgett

ps octane number requirements are liable to go down at higher elevations. 
The gas you buy in Denver will not be the same as in Orlando.