There are two and only two possible causes for this problem:

1) The fuel gauge sender is dirty. Having tried every possible type of chemical fix, the only permanent solution to this is to take the sender apart, carefully wipe off the resistance wire, and reassemble. This problem is much more likely in a Diesel car. (BTW, the base chemical in MMO is Stoddard's solvent, AKA paint thinner.)

2) The fuel gauge damper coil has a broken spindle. If you pull your dash pod and examine the innards of the fuel gauge, you will find that there's a choke coil wrapped around a plastic spindle. This is what gives "slowness" into the reaction time of the gauge. If a physical shock, like driving through a pothole, has broken the spindle, the coil can intermittently ground against the steel case of the gauge and cause the needle to blip. The solution is to simply use some electrical tape to isolate the coil from the gauge.





You can usually tell the difference between these two conditions: the first will tend to occur at a particular fuel level, the second can occur randomly regardless of level.