Given that your chemical expenditures are around 6-7% of your gross, it is an important factor of production. What every operator should be looking for at each stage of the wash cycle is using the best possible solution at the lowest possible cost.
Obviously, having only one supplier places the responsibility for how your customers vehicles come out squarely on their shoulders. It also gives you a continuity and synergy of prodcuts assuming that each product plays well with the others.
However, in my 36 years in the business, I've never found that one company has all the best products all the way down the line and for the most reasonable price. Currently we use our own pre-soak that we have made for the past 25 years. We also make our own foaming prep solution from 50# bags of a product called Witconate Flake. We also use this for our first foam arch after the pre-soak. The CTA, Polish, Rain-X, drying agent and tire shine are all Ecolab products. They've got a helluva line of very competitive products and the service is great too.
Do beware however if you do experiment to try only one new product at a time. Remember that a cheaper drum does not necessarily save you money, just as a more expensive drum doesn't necessarily cost you money. It depends completley on the cost per application vs. the amount applied per application - that is, the number of cars per drum. In my book, you do not change solutions for the sake of change. It has to be demonstrated that quality of the cars coming out of the tunnel not only has to be better that what you are currently using but also at a significant savings. Otherwise, why change at all?
Most importantly, if you do experiment remember that it takes time and your on-site evaluation of the prooduct. That is, are the cars cleaner, shinier, dryer, etc.?.
