“Expensive soap” and “cheap soap” mean nothing until you put a number of washes next to them. A $30 jug can end up costing you more than a $100 pail, and that's not a paradox, it's arithmetic.
A formula with just two numbers
The chemical cost of one wash works out like this:
Jug price ÷ Number of washes it gives = Cost of one wash
You know the first number. Almost nobody works out the second, and that's where the whole difference hides. The number of washes comes from two numbers as well:
Jug weight ÷ Dose per car = Number of washes
Note: weight, not volume. Concentrates are denser than water, so 5 liters weigh almost 6 kilograms. Count in liters and you'll come up about fifteen percent short on yield.
Running real numbers
Start with what we know for sure. The 1.3 gal (5 L) jug weighs 5.8 kg (12.8 lb). The recommended dose per passenger car is 50 to 100 grams (1.8 to 3.5 oz). Take the low end, 50 g: that's a clean car on a foam generator.
5,800 g ÷ 50 g = 116 washes. We round that down to “about a hundred” on the label, and for good reason: some product always stays on the walls of the jug and in the hose.
Now the price. Online, the 5 L jug sells for $34, marked down from $89. We'll use the price people actually pay:
| Size | Weight | Washes | Price | Per wash |
|---|---|---|---|---|
| 1.3 gal (5 L) | 12.8 lb | ~100 | $34 | ≈ $0.34 |
| 5.3 gal (20 L) | 45.9 lb | 400+ | $99 | ≈ $0.25 |
About a third of a dollar per car is the range where touchless chemistry lives. Keep it in mind as a benchmark: if yours comes out at $1.35, something is leaking, whether it's the ratio, the equipment or the purchasing.
Why small packs cost more
Packaging costs money, and the smaller the jug, the bigger the share of its price that goes to plastic, cap, label and shipping. With a 1 L bottle you buy roughly the same plastic as with a 5 L jug, but five times less product.
The practical takeaway is simple: small packs only make sense as a trial. You buy a liter to find out whether the formula suits your water and equipment. Once the answer is yes, buying by the liter is just a way to overpay for plastic jugs.
At a busy location it's even more obvious. One 20 L pail is one delivery, one spot on the shelf and one injector setting for weeks, instead of twenty small bottles that also run out at the worst possible moment.
Where the math lies
Every table online, this one included, assumes ideal conditions. Reality differs in four ways.
The dose isn't 50 grams
Fifty is a clean car in summer. In winter, with de-icer and salt on the body, the dose heads toward a hundred. An SUV or a semi has more surface, and everything grows with it. If you don't want to be disappointed, use the upper bound: 100 g per car gives a number twice as bad, and a more honest one.
Water can be hard
Hard water doesn't “eat” more chemical directly, but it makes you keep the mix near the stronger end of the range to avoid streaks. The extra usage adds up just the same.
Equipment sets a twentyfold spread
A foam generator runs at 1:80–1:120, a handheld foam cannon at 1:5–1:7. That's not a typo: the gap is more than tenfold. A busy wash running foam cannons will go broke on chemicals even if it buys them at half price. More on this in our equipment breakdown.
Some product just goes down the drain
Leftovers in the hoses, flushing the system when you change chemicals, spills when you transfer it. Budget about five percent. It's not critical, but it explains why 116 washes on paper become a hundred in practice.
How to work it out for your location
Every manufacturer's table, ours included, is approximate by definition. You already have the exact number; you just need to dig it out.
- Take a period in which you used a known amount of chemical, say a month.
- Count how many cars went through in that period, from the register or the log.
- Divide what you spent on chemicals by the number of cars.
That number accounts for your water, your ratio, your waste and the heavy hand of the night shift: everything no table includes. That's your real cost per wash.
From there you can work on it: lower the ratio until quality starts to slip, change equipment, move to bigger packs. But first you need a baseline.
Key points
- Compare the cost per wash, not the price of the jug: price ÷ number of washes.
- Count washes by weight, not volume: concentrate is denser than water.
- Touchless chemistry should cost tens of cents per car; much past 70 cents means something is off.
- Small packs only make sense as a trial: you're paying for plastic.
- 50 g is summer and a clean car. In winter, figure 100.
- Get your real number from a month of your own data: it beats any table.