It makes sense to me. How does the product know to target the deposits and not the seals? Chemically, there's not a whole lot of difference between deposits and seals. If you soften one, you'll probably soften the other. Plus, some of the deposits can sometimes act as a seal. It's walking a thin line when you use mechanic-in-a-bottle products, and knowing how to use them without getting too aggressive with the product.

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95 E320 Cabriolet, 169K