how much compression is too much?

It depends on your blend. Can holds 32 ounces.

105 octane would be 5.33 gallons per can. That equates to $41.85 for 5.33 gallons of 105 octane fuel. $7.85/gallon
101 octane would be 8 gallons per can. That equates to $48.96 for 8 gallons of 101 octane fuel. $6.12/gallon.

ETC....

If you buy it by the case on the website they give you free shipping.