<VV> Kind of gas for 62 Monza 110

[Rad Davis]

All true.  A little more detail:

Octane  ratings come in three flavors: Research, Motor, and Pump, which is the government-mandated average of Research and Motor and is displayed on gas pumps in the US.  Research octane numbers are usually a few points higher than Motor numbers for the same fuel.

You care about this because the rating system GM used to put the number in the owner's manual back in the '60s was Research octane.  What this means is that a 90 pump octane gasoline you buy today likely has a research octane number of 91-92 and a motor octane number in the high 80s.

Air cooled engines have high octane sensitivity relative to head and oil temperature.  You'll likely find that a deflashing, careful clearance adjustment of the fan, and, if it's hot, removal of the bottom shrouds is worth 2-4 octane points in knock sensitivity.  Likewise, changing to a folded fin oil cooler can help if you work the engine hard (FCs).



On Wed, Jul 27, 2022, at 2:18 PM, Bryan Blackwell via VirtualVairs wrote:
> Hi AJ,
>
> IMHO, octane is far more important than ethanol-free.  While 93 is 
> best, 92 generally is ok too.  I've never tried 91, I would guess you'd 
> want to back the timing off a degree or two if that's all you could 
> find.  If you're concerned about alcohol content, try one of the fuel 
> stabilizers for alcohol blended fuels.  I'm assuming the 110 came out 
> of a later Corvair, you might mention what year exactly (if you know) 
> for any questions that require specific answers, as there are minor 
> differences in the carbs and ignition over the various years that can 
> affect certain settings.
>
> --Bryan
>
>> On Jul 27, 2022, at 12:37 PM, A.J. Stone via VirtualVairs <virtualvairs at corvair.org> wrote:
>> 
>> Would appreciate guidance on what kind of gas is best for a 62 Monza 110.
>> The owner’s manual calls for premium, which I am assuming is 93 or better octane.
>> I can only find 87 octane ethanol free gas, but no premium ethanol free gas.
>> Would it be better to use the lower grade ethanol free gas or should I use the premium gas with the ethanol additive??
>> Thanks 
>> AJ 
>
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