WEST Yorkshire garages were put to the test in an operation carried out by Trading Standards officers.
They were responding to complaints about car servicing and targeted the 10 garages with the most complaints.
The operation follows a rise in the number of complaints to the Consumer Helpline about cars in the last few months.
Cars were examined by independent engineers before being taken to the selected garage for a full service.
The engineers rigged the vehicles with a number of identical minor faults in order to test the standard of servicing.
A Trading Standards spokesman said: "This is a tried and tested method to check that the service had been carried out accurately.
"There was cause for concern in each garage. For example only one garage out of the 10 managed to check and inflate the spare wheel. This is despite the fact that most of the garages had ticked the service schedule box stating that the spare wheel had been checked.
"In addition to this one or two garages were over-cautious in recommending repairs and in many cases garages had failed to top up windscreen washer bottles and power steering pumps."
The majority of the garages failed to check at least two of the service items.
On a more positive note, none of the garages committed an offence under the Trade Descriptions Act - all the parts they charged for had been fitted.