Out of Fuel? Read that

If you a new or experienced player and is struggling with fuel at beginning of a career mode, this guide is for you
Follow these rules an you're ok

Rules

1 - Never use more than one fuel tank on your creations.
You will silently lose fuel every time a creation is back to workbench
More fuel tanks more loss. (Premade or custom fuel tanks have the same issue), need more fuel put a larger single tank... If you are interested, it is a bug and you can replicate this issue reading the final part of this guide

2 - Aways use eletric when testing a new creation. After creation is all ready you can use your Diesel engines. Every fuel tank when connected to engines lose fuel when back to workbench. Imagine if you need to test a creation 10 times. You will lose 10 x 20 liters per fuel tank. That is huge

Bug Tracker Report

This issue have been reported multiple times to bugtracker but developers dont want to fix so am here to help you with this workaround
Dont even try to report again, the ticket will be closed right away.

Continue reading to try the bug and see for yourselfs
https://geometa.co.uk/support/stormworks/23978

Fluid tanks (premade and custom) do not refund the full content upon return to the workbench.
Loss of fuel can be huge taking into account that a vehicle can return to the editor several times for modifications during construction. The amount of fuel lost varies. For diesel it is around 30 liters per tank, for jetfuel losses go from 200 to 500 liters in some cases.
The economy of career and classic career mode revolves around these resources, new players can run out of gas without even go on their first mission.
The loss increases as new fluid tanks are connected to the system. 10 tanks can lose 300 liters at once.
Workaround for now is only use 1 huge fuel tank and use eletric to test vechicles and only spawn vehicles with fuel after complete construction.

Steps to reproduce:

1. Build a floating box with 2 premade tank connected (with pipes or directly) full with diesel or JetFuel

2. Check fuel storage

3. Return to workbench

4. Spawn the box again

5. Check fuel storage - There is significant loss

Expected Result: There should be no difference in the fuel in the storage since the vehicle was spawned within the editing area and there was no consumption from any source that generates power.

Actual Result: There is a considerable loss of fuel, taking into account that a vehicle can return to the editor several times for modifications during construction. The amount of fuel lost varies. For diesel it is around 30 liters, for jetfuel losses go from 200 to 500 liters in some cases

[DangerCal]

Just pump the fuel back to storage before returning your craft, problem solved. Obviously it is a little annoying. But at least you can test your engines.

[FlyMaker]

Do you have any suggestions? The only permanent fix is not on our hands. Devs don't care so dont expect any proper fix

[SunshineStrapony]

Rule 1 - Useless. Some buildings require multiple tanks. Just use valves on second tanks
Rule 2 - Useless if you testing various engines configurations

[Invention64]

Huh, so that explains why I ran out of fuel before leaving in my first save