I have run it down below a quarter tank. I have heard of some guys having a problem with the Titan tank when low and on an incline. I have not, and increasing the tank was one of the best mods. Per Titan tanks the issue was with the Nissan unit and not their tank. Their are two options the Titan a polymer and Trans flow a steel tank. Both are good and each has pros and cons for you to consider. If you choose the Titan tank there is an important step in tightening the flang and pickup unit in the tank, tighten to spec wait 15 minutes and retighten again, do this three times. They also said I should see three and a half to four threads of the bolt above the nut. Get this wrong an you will have leaks. Summit ships the tank free.