There is a big difference between the over-the-counter products and the professional products used by Quick Change. The strength and chemical composition is a completely different formula. The over-the-counter products are primarily for maintaining the system as opposed to the professional ones that will actually remove deposit buildup and restore original performance sometimes increasing gas mileage by 10 to 15% depending on the condition of the injectors. When you consider the price of gas these days, the cost of having the fuel system cleaned will pay for itself in gas savings. Check the coupons page on our web site for our coupons.