How full to keep the gas tank?

I got 180,000km on my 1998 Civic Hatch. I normally fill up when there's only 7% to
15% left in the tank. In several occasions, I've filled 44 litre (the tank can take
45 litre capacity).

In the summer, when the weather is hot, I usually try not to go under 7%.

Pars

 

eh- better than some, worse than others. thanks to the internet, we can
share problems and solutions like this. id rather have a common, fixable
problem than an uncommon, hard to fix one.

 

Despite all the above "calculations" it does happen that water gets into
fuel - in gasoline, it has more to do with the hygroscopic nature of some
of the gasoline components and aromatics are particularly prone. It
happens less now in cars with the vapor control systems but it happens even
in storage at the refinery, bulk plant and gas station... and refineries &
bulk plants usually have floating roof tanks. In your car tank,
temperature fluctuations can cause separation and once separated the water
tends to stay separated, on the bottom of the tank.

Where ethanol is added as an oxygenate, the problem is quite severe... to
the extent that the refiners add it at the final load point when the
road-car is being filled for delivery. It was found that blending in the
ethanol to the product tanks at the refinery resulted in too high water
content at the final delivery point. This was aggravated by the fact that
all pipelines have some water in them which got picked up during the
transfer.

Since ethanol forms an azeotrope with water, any water separated out, which
happens at >~0.6% water at normal ambient temps with a 10% ethanol/gasoline
mixture, will pull the ethanol preferentially from the hydrocarbon
components and since ethanol has a high octane number factor, 112(?), you
can get quite significant effective octane reduction of the remaining
hydrocarbon mixture.

Rgds, George Macdonald

"Just because they're paranoid doesn't mean you're not psychotic" - Who, me??

 

It depends on the conditions. If the car is being driven the fuel sloshes
around quite a lot - quite an efficient method for increasing oxygen
uptake.

There's very little unsaturates, like olefins, in gasoline now, mainly due
to emissions regulations. In fact gasoline forgetfully left in my
lawnmower or snowblower for several months is in quite good condition now,
compared with the results of a few years ago.

Rgds, George Macdonald

"Just because they're paranoid doesn't mean you're not psychotic" - Who, me??

 

If the car runs, there is fuel in the pump, it'll stay cool enough. Many
cars have pumps outside the tank - they don't overheat.

When you think you need gas because you might run out, get some.

EFI cleaners (A good one, not CRC or Wynns or some other cheap gas-in-a-can)
are good to run through periodically - they help soften any deposits which
can build up, but the main thing is they emulsify with water in the tank so
it can be burnt in the engine.Water in the system is bad

Allan

 

Whats more, many of the pumps are located at the top of the tank, and the
pickup sits underneath it. The pump could be uncovered at only half a tank
Look at a nissan skyline

Allan