QUOTE (B@T "El Argentino" @ Dec 1 2005, 07:03 PM)
QUOTE:
Just wondering, why would the extra gas be wasted??
I couldn't find my original source but I did find a second confirmation that "topping off" is not worth it. Here goes their explaination, from Auto Repair for Dummies, page 15.
"Never 'top off' a tank by adding fuel after the pump has shut off automatically. If you overfill your tank, the fuel may overflow the fill hole or leak out onto the road through an overflow outlet. This is not just a waste of money; spilled gasoline ruins asphalt, pollutes the air, and is a fire hazard. This kind of leakage is especially prone to happen if it's a hot day and the gasoline in your tank expands."
The flip side to this is you also don't want a tank that is always riding on empty either. On page 269 it states that an empty tank has more air inside, and on cold mornings this turns to water vapor. The water collects on the sides and rusts the tank from the inside out. After a while, this rust settles at the bottom of a tank, and is fine so long as the pickup doesn't scrape the bottom and pick up these "coffee sediments", which can occur when the level of gas is very low. Some in-tank fuel filters can prevent the problems associated w/ floating rust, but even these filters will eventually become clogged and cause problems.
I know this for a fact. My '81 280zx apparently had tank rust issues because one day I went to go to work only to have the car stall soon after it started. Several tries later, I called into work and said I would be late. Turns out that car sat for almost a month all the while I tried to fix the problem. I bought a new fuel filter, rubber lines, pressure regulator, etc but nothing would get the damn car to even turn over. Finally, as a last ditch effort before I was going to have it towed, I pulled off the line that runs from the tank to the pump. I could see a big (size of a peanut M&M) piece of rust wedged in the inlet so I took a golf tee and put it in the opening, then punched it. I hooked everything back up, turned the key, BAM!, sputter, sputter, back to life! After that I always kept the tank above 1/8-1/4 never had another problem. Sorry for the novel. Mak