Most fleet wash bids look interchangeable, because the deliverable — a clean truck — is easy to describe and hard to differentiate on paper. The differences that matter are in what happens around the wash.
Six questions
Where does the water go?
The single most useful question. A vendor with recovery equipment answers immediately and specifically — drain seals, vacuum reach, tank capacity, disposal. A vendor without it changes the subject to their soap. The discharge is your liability, so this is not a technical curiosity.
What chemistry are you using on my aluminum?
An acidic product that brightens aluminum will etch galvanised steel, and anodised aluminum must never be acid brightened at all. A crew that cannot describe the difference will find out on your equipment, permanently.
When can you actually work?
A programme that requires units stationary during business hours is a programme that never runs on a working fleet. Ask specifically about overnight and weekend windows before, not after.
What do I get in writing?
A per-unit condition report is a dated record of what each unit looked like, which matters the day a damage claim appears. Washouts should carry a dated wash record. Ask to see the format.
Are you insured for work on my site?
Ask for a certificate before the first visit, and check that the coverage matches the sites they will actually work — plant and port properties frequently require more than a standard policy carries.
What happens if a unit is missed or done badly?
The answer should be that they come back. A vendor who has not thought about it is a vendor you will be arguing with.
The bid that is cheaper for a reason
Containment equipment is a real capital cost — recovery vacuums, drain seals and booms, transfer tanks — and an operation that has not bought it can genuinely underbid one that has. The saving is real. It is just being paid for by whoever owns the property where the water ends up.