In hot climates like UAE, the fluid will evaporate through the hole faster than consumption. I suggested putting a balloon over the hole to deal with expansion but it's a little more complicated as you would want a way to let air in when you use the sprayer. Prob just putting the balloon on when it's 70f at night would be enough.

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E53 / M54 2001 3.0i gas LHD (pair of them: his & her)