How to tell if a mechanic actually changed your car fluids
Car fluid looks identical before and after a service because technicians can write anything on the invoice without actually doing the work. This makes it impossible to verify if you got what you paid for or if the fluid was just partially sucked and filled.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
- 1Checking fluid with a testerDid this help you?
- 2Sucking fluid out of the reservoir and replacing it manuallyDid this help you?
- 3Cracking a bleeder valve to check fluid clarityDid this help you?
- 4Taking out a sample with a turkey baster into a clear glass jarDid this help you?
- 5Bringing your own oil and watching them put it inDid this help you?
- 6Asking the shop to put the brand name, viscosity, and amount on the invoiceDid this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“The fluid looks exactly the same as it had prior to the flush and feels like it either wasn’t done or just sucked and filled.”source ↗
“You can't. They can put whatever they want on the invoice doesn't mean that's what the technician actually used.”source ↗
Where this came up
People with this problem also raised
- 12Fluid leak right after an oil change or service
- 16Should I change my transmission fluid at 60k miles?
- 6How do you check automatic transmission fluid correctly?
- 2How to tell if automotive fluids are counterfeit
- 21How to choose between multiple equivalent automotive fluid specs
- 5I accidentally put the wrong fluid in my car