Alright. I got a 1990 F150 straight six that has two fuel tanks. The front tank I have been using since I have gotten the truck back in December. Before it came into my name it sat in the driveway since near the end of 2012. I switched the fuel gauge to the rear tank and it says the tank has half a tank of fuel left. Considering that I'm not able to drop the tank to remove all the old fuel. What should go about doing? Add some kind of fuel additive to it and fill with fresh gas?

 

I would disconnect the fuel line into the fuel filter, switch to the rear tank, jumper Pins 2 & 6 on the diagnostic port, then switch the key to the Run position. This will turn the rear pump on full time so you can drain the tank.

 

I can't remember who makes it (Stabil, perhaps?) but there's a product to 'rejuve' old gas. Most marine shops or perhaps even Walmart sell this. You don't seem that bad off as you have only 1/2 tank. I'd use this, along with fresh gas & burn it up as fast as you can. Run it to near empty then re-fill with fresh fuel. You should be fine!

 

This I was planning to do once I am finished with the fuel in the front tank which right now has a little over a quarter tank left. So considering I'm not driving constantly I have a few days. Just need to find this product your talking about.

 

Sorry....old fuel is just that. Trying to rejuvenate it is pointless IMHO.

 

Don't do it, if you can help it. Old, stale fuel turns to varnish. It will burn, sort of but will leave a glue like residue. The next time someone goes to start....

 

Even if I do somehow drain the tank won't there still be something left from all that fuel in the bottom of the tank?

 

There will be a small amount of fuel left, yes. Refill the tank with fresh fuel. You should be good to go.

 

Well... I do have a disconnect tool for the fuel filter since I haven't gotten around to replacing it with the one I bought since I been busy. All I would need to do relieve the pressure and then find a place to put all the old fuel. The rear tank is 16 gallons. Which if the gauge is reading right it has around 8 gallons in it.

 

Here's what I did with the old rotten gas in mine.............

 

It depends. Fuel left long enough (years) turns to pitch, or asphalt basically. They can be cleaned out, but it's a stinky, messy job. New, replacement fuel tanks are a pretty good deal price wise depending on what you value your own labor at. Ethanol fuels are prone to phase separation and do not store as long as pure gasoline. Wide temperature swings in a half empty tank invites heavy condensation at night as the tank will "breathe" the atmosphere.

Get a long siphon hose and pull a sample from the bottom of the tank and see what you think. Is it cloudy or yellowed, oxidized, tar *****, stinky like paint? Or sparkly clean and smells fresh gas?

 

If the fuel is old, smells like he77 then don't waste your money on snake oils. We clean 350 tanks annually and todays gasoline is garbage.

 

"stabil" and other fuel stabilizers work when you add it BEFORE putting a machine into storage ... although i doubt they would work for 3 1/2 years. there is no additive that i know of that will rejuvenate old gas after the fact; so don't waste your time/money. nor is it a good idea to add fresh gas to the half-tank of stale gas. in the old days, you might have gotten away with it, but as previously stated, gas doesn't keep well nowadays, and 3 1/2 years is waaaaaay too long to have any hope.

 

Figured forget this and just fill up my front tank. Too much hassle for what I'm going through right now. Once I finally get a job which is what I'm going through right now I will worry about it then. Just got to add it to my list of stuff for future projects on this truck.