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viewtopic.php?f=2&t=4With fuel tank would be good to clean tank and replace fuel filter (fuel cleaner might mave move the junk from tank to filter. Chances are that has never been touched. If guage is giving you dud readings might be problem with float in tank. Also could use some carb cleaner to remove deposits.
Another site to look at is ecomodder.com. The swifts/geo's are popular and if frugal driving is the game there are some good tips there.
As to painting it, I would definitely rethink black. Read up about how "colour" (or color

) works. Your best bet is white. Not only does it look cleaner (ie. dirt doesnt show as much) it will reflect heat more efficiently. Less AC usage means less power draw, means better MPG.
Note on your new plugs I believe you have swapped to a set with a larger gap (hence the "11" designation). NGK BPR6ES with standard gap of 0.8mm over the 1.1mm plug you have I believe are probably your standard plug. This will impact economy as they will probably burn a little hotter and wear faster. You
might see better economy initially but you will need to replace plugs more often to maintain this as mileage will go in opposite direction after a point.
Best option is a factory copper plug with factory gap or a fine electrode at preset gap - usually 1mm (will potentially improve mileage but I dont think it is worth it for price of most of these plugs).
Note that there are a couple of different 1.3L engines. Presume yours is the 1.3L SOHC carb engine.
On the doors, do you mean handles or window winders? If handles might be that some of the plastic clips holding the push rods have come off or more likely broken. Some lube might help free things up as well as I imagine there is a lot of dust that's getting into the door cavity.
Gas hatch struts are easy to get hold of. There was another thread here by a north american talking about where they got theirs from and the warranty included meant he got a few free replacements over the years.
I would check your spare as well as chances are its the original tyre and rubber might split easily after 20 years of non use...
Enjoy car. These are good little grocery go getters and very reliable.