Triumph Repair: premium or regular gas, high octane fuel, fuel mileage

Question
QUESTION: I have a 1959 TR3.  This was anniversary gift from our children.  My question is what does it use for gas...regular or premium?  I thought because of the high compression engine it would be premium. Any answer would be appreciated. Thanks.

ANSWER: Hi David,
Yes, all high compression engines should run high test gas. The higher the compression the higher the octane rating is necessary and not an option. The same is true in the other direction, the lower the compression the lower the octane rating necessary.

If you run low octane fuel in a high compression engine you are in danger of preignition and detonation which are very destructive to the engine. If you run high octane fuel in a low compression engine you are in danger of a very slow burn that tends to burn the oil off of the cylinder walls and it will tend to over heat the cylinder walls. Both cases will decrease horse power and fuel mileage. The fuel must match the engine. Some people alter ignition timing to be able to use fuel that was not meant for an engine. This can be done on moderate compression engines if you know how and are careful.

Howard

---------- FOLLOW-UP ----------

QUESTION: Hi again Howard

One more question....
If low octane level fuel was used in one fill up in my 1959 TR3 Truiumph, is it necessary to siphon the gas out of the tank and refill with high octane fuel or can you mix the two until you need a fill up again?  This happened only one time.
Thank you.

Answer
You can just add high octane fuel to the tank depending on how much of each you have. If the tank is full and not much room for much high octane fuel, just get a bottle of octane booster from any autoparts store and add it. You should then warm the engine up and raise the hood and let it idle and give the throttle a few quick blips from idle to see if you get any "Pinging". If you do, temperately retard the timing until you don't get the "Pinging". Don't use that retarded timing when you refill with the higher octane. Set the timing back to specs.
Howard