Running on fumesOne of the key factors in a lot of my flying has been my jump range. When trading, and trying to find the highest credit profit per hour anything you can do to reduce your flight time really helps.
By increasing your jump range you can make more systems available in one jump, or reduce a triple-jump route down to a double-jump, saving you time and money on your route.
Running on fumes is a good tactic for any ship, but specifically for the low-tonnage vessels as your fuel tank is a higher proportion of your total tonnage. That fuel has real mass and decreases your effective jump range accordingly.
To pick an example, lets start with the smallest of ships, the Hauler:
A shop-floor Hauler isn't up to much but if you max out the Cargo and give it a slimline refit you have a 22T ship for just over 80,000 Credits.
The Hull and systems on this ship only weigh 18.5T - so when you add 22T of cargo and 4T of fuel you have doubled the mass of the ship - and halved its effective range. Its fully Laden weight is 44.5T and it'll have a range of 9.4 - 18.5LY
That 4T of fuel is now a significant 10% of the mass of the ship, running on a half tank isn't going to net you much (with a slimline Class-D FSD) but it'll add 0.5-1.0Ly onto the effective range.
Again the Cobra has the same story. Lets spend..About 1M Cr on a Cobra3 with a Budget Class-C refit across the board and some upgraded cargo space. This ship is going to weigh 288T fully loaded and its 16T Fuel tank comes out less that 6% of its total mass.
Running on fumes is still going to add 0.5Ly to your effective range, and if that was the difference between a single jump and a double, you could shave minutes off your round-trip route time.
A lighter ship also uses less fuel per jump, so you save money by jumping light. Running on fumes only matters if your Credit-per-hour bottom line is really tight, but like most of us playing time is limited and sometimes these tricks can make all the difference.
Reducing scoop timeRunning with a lighter tank will also reduce your fuel consumption and drop your scoop time on long journeys too. Saving only a few minutes can be a boost to your credits/hour profit line if you really care about peak efficiency.
Just be VERY careful not to get stranded - if its an unfamiliar route then keep just enough in the tank to jump to a known safe, scoopable, star.
Have fun playing with different loadouts and as always, fly safe.