Not more than a 50/50 mix, but less
antifreeze is better. Water (distilled) is more efficient at removing heat. I noticed that you live in the North. If your Cobra is exposed to temputatures below 32 degrees, you should check the ratio to be sure you are protected during very cold weather. Most Cobras are stored inside during winter months and do not need a lot of
antifreeze to protect them. Too much
antifreeze makes a Cobra run hot. We know this from experience.
Dwight