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O.k. so today a weird idea popped in my head.

What if I only filled my tank up half way, say, 5 gallons or so, instead of filling it up all the way? I would still get plenty of range (350-400 miles), and would decrease the weight by about 30 pounds. (Gas weighs about 6 pounds per gallon) For an Insight, that's about a 1.5% savings in overall weight.

What do you think?

Eric,

This could be a very off-the-wall response: Gas Thiefs are back (http://www.msnbc.msn.com/id/18574063/), and they are after big tanks.

_____________________

On a strictly fuel economy discussion, some gas might evaporate. Does it evaporate fast enough to make a difference? Don't know. I've read letting the tank completly empty gives sediments more of a chance to get into the engine.

This is interesting to ponder...

Eric,
On a strictly fuel economy discussion, some gas might evaporate. Does it evaporate fast enough to make a difference? Don't know. I've read letting the tank completly empty gives sediments more of a chance to get into the engine.

This is interesting to ponder...

I guess I'm not so concerend about any evaporation. That seems like it would be small.

As far as sediments, well.... I always drive my tank well below the last bar on the fuel gauge anyway. Changing how much I fill up would not affect this habit.

One concern... will filling up in this manner make me lose some accuarcy when I calculate my gas mileage by hand?

Hi Eric:

___During the FEH Experience, the Ford engineers had calculated that every 300 #’s of weight lowered an FEH’s FE by 1 mpg. I am going to assume the Insight would lose maybe 3 - 4 mpg with 300 #’s and maybe .2 with just 30 #’s. Considering the ingress/egress from most stations, I try and visit them as little as possible so a topped off fill and huge range to avoid the pump congestion FE hit overrides the 80 + #’s of excess fuel in the case of the Accord. I know Dan (Krousdb) loved running a half fill but at the (2) stations I usually fill at are far too chaotic and the possibility of losing .1 or so mpg over half a tank because of having to visit the darn things dissuades me from visiting any more then I absolutely have to. I hate visiting the darn things as you can tell :D

___Good Luck

___Wayne

...I've read letting the tank completly empty gives sediments more of a chance to get into the engine...

I don't like running on a low tank but for other reasons.

I've replaced a couple in-tank fuel pumps (on 15-18 year old cars with hundreds of thousands of miles on them). I suppose I'm not the only one here who has done so. Fuel system's pickup is at the lowest possible point in the tank. At least in our cars there's a filter at that point for protection of the rest of the system. Not sure if a filter there is usual for most cars or not.

My concern is fuel sloshing around in tank. If fuel level is very low there's a likelyhood of air or vapor bubbles in the fuel even at the bottom of a nearly empty tank; that would not be ideal when this gets sucked into the fuel line.

I think there's something to the often voiced concern re. debris at bottom of the tank, however that's where the pickup is so the system must be able to tolerate whatever debris normally sinks down. It sinks to bottom regardless of fuel level. Debris that floats, that's another matter. When level gets low then any floating debris may meet the pump intake.

Another good reason according to a good mechanic friend is that most fuel injection cars have the fuel pump located in the gas tank, and it actually depends on being SUBMERGED in gasoline for LUBRICATION! Premature bearing failure can occur from keeping tanks below 1/8-1/4 full.

I agree that it is better not to go much below a gallon or 2, especially in a small tank like the Insight's. In tank fuel pump replacements are messy and expensive.