and is it up to the gas station, or is it mandated by law?

 

good ???

 

The screens inside the tanks only get changed when ther is a problem.
Remember that once there is no suction on the screen then any sediment will fall back to the bottom of the tank.
Never buy gas from a gas station when the tanker truck is there, and wait a couple of days for the sidiment to settle back to the bottom.
The fule filters get changed whenever the gas station wants to. And also remember that a dirty fuel filter will just restrict the amount of gas that comes out of the pump, it will not let dirt through, it will actually filter better.
The gas stations have a water level meter in the back, to high of a water level and a alarm goes off. What they do next depends on the gas station.
The manager must take tank readings with a stick. Ever see the really long wodden stick on the side of the gas station? Ususally inside a PVC tube. They pop the cover off of a tank and dip it to the bottom, pull it up and read the side, it is in inches.
Use the chart inside and the inches tells them how much gas is in the tank. They compare that to the electronic level meter inside, if they have one.
When I ran the vacum truck for Safety Kleen I had to do the same thing to figure out how much sludge/liquid I sucked up so that I could invoice the customer corretly.
Looking down inside a 2500 gal tank full of crap is a scary thing.

 

i see

 

Thanks again for your comments. I have the vehicle back now with new plugs and leads. Still misfired once or twiceand the check engine light is still on, but usable. The dealer reckons that the ignition coils still need changing to kill the light but says its ok to use. With the price of coils around an equivalent of $50 in the uk and ten times that here its going to have to wait until our next trip over here. In the meantime we're off to the coast for a few days.

I'm still curious myself and will post an update once its got a few more miles on it.