2005 f115 runs rich surging no apparent loss of power.

[TownsendsFJR1300]

Excellent!

So we think the issue was bad fuel then?

[mahtzo22]

Yes. Next step is to run her. I think the bad fuel is probably gone from the tank or mostly gone (approx two tanks, not counting the oldest fuel, have been run through since the problem initially came up several months ago). If the problem returns, I'll try replacing the filter again and put some more fresh fuel in. I suppose it could take a few tanks and several filters. What do you think? does this sound reasonable?

[TownsendsFJR1300]

I recently drained my tank of old fuel using just the primer bulb and tank pick up.. (About a 60 gallon tank)

About 22 gallons, most of it over 1.5 years old but stabilized. Smells/looks brand new (I use K100).

I've since been using the old fuel in the bike, mower and SUV W/O issue..
Actually, the bikes running better with it, perhaps the RingFree or just cooler weather the reason.

[mahtzo22]

right now I have approximately 45 gallons in the tank (approx 55 capacity). I treat with Marine Stabil each time I fill up. (occasionally I forget). Most of the first batch (what I think was the bad fuel) was probably 6-9 months old when i first had issues in July. I have thought about draining the tank but think I will wait to see if the fuel is fine now. (I think the first batch caused the 2 micron filter to clog enough to cause issues but of course new gas didn't fix the issue because the filter was still clogged.) I have relatively new fuel in the tank now. Hopefully I am right. If not, I guess I'll have to drain the tank and use it up in my truck.