Old fuel in stored vehicle?

Messages
237
Location
SE
I recently acquired a vehicle that has had the same fuel sitting in it for 10 months at about 1/2 tank. It took it in for a GA emissions test and the tech mentioned a bad smell (stale gas I presume). It passed the emission test (gas cap ok and computer test). He recommended draining the tank and filling it with premium fuel for the next couple tanks. The vehicle runs fine. Do I really need to drain the tank vs just filling it (and maybe use some kind of additive like Techron Concentrate, Royal Purple Max-Clean Fuel System Cleaner and Stabilizer, Startron or something else etc ?
 
Messages
258
Location
MS
If it runs fine now, just fill it with premium fuel, add a cleaner (I prefer Marvel Mystery Oil) and drive it out ... that is, if you can use up the whole tank in the next month... if you can't drive it out in the next month, then consider siphoning out most of the fuel that's in it now and then refilling with premium fuel and MMO... and follow on from there...
 
Messages
920
Location
Muncie, Indiana
There's no reason to use premium fuel in a vehicle that doesn't need it. But if you wish I guess you could get a 32 oz bottle of techron, Put half in the current tank and try to run it out, then run the rest in the next tank.
 
Messages
258
Location
MS
Not knowing whether the vehicle requires higher octane or not, I recommended premium fuel to bring up the octane level of whatever is in the tank now as it's evidently old and may have degraded... especially if he's going to drive it out... and in the follow up tank due to some premium fuels having higher detergent levels than their regular fuel... again, not knowing what brand of fuel the OP will be using... so no harm, but potential benefit...
 
Messages
35,860
Location
ME
I'd drive it as is, gently, to get down to 1/8-1/4 then refill with fresh. When you mix a gallon of fresh milk with a gallon of sour milk, you get two gallons of sour milk. LOL When you refill, do a mix of 87 and high-test. The 87 will be fresher due to turnover and the high test will take care of any low-octane stale fuel remaining.
 
Messages
1,127
Location
Wisconsin
I had a car sit with 3/4 tank sit 3 years Started right up, topped off with fresh e free and drove, no cel no issues Modern cars have far fewer issues sitting as the tank and other components are sealed up well.
 
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Messages
4,112
Location
WA
I'd throw a bottle of Stabil Red in there now just in case you have any water then run a can of Berryman's on a full tank once it's empty to address any gum that may have formed in the system. Be on the lookout for poor mileages and any misfiring. Of course dumping it all isn't a totally horrible notion but it may not be needed.. thing is you won't know until you drive it some more. I would try and run that fuel asap too..who knows if corrosion has started, whereas fresh fuel will help stop/combat any.
 
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Messages
4,641
Location
Suburban Washington DC
Originally Posted by rkpatt
I recently acquired a vehicle that has had the same fuel sitting in it for 10 months at about 1/2 tank.
10 months is nothing. Don't worry about it. Drive it like you filled up last week. I've had cars with up to 8 year old gas run fine.
 
Messages
5,381
Location
San Francisco Bay Area
Modern cars with sealed fueled systems don't really have too many problems with stale gas. The biggest problem from fuel storage is water contamination if it's vented, as well as oxidation. That's not much of a problem with modern cars because the tank is pressurized with fuel vapor, which I believe should form a vacuum when it cools. My wife's car was sitting in our driveway barely driven for about 9 months after the transmission died. I did limp it (it might work for 1/4-1/2 mile at a time before I had to shut it down for a few minutes) to a guy who diagnosed and replaced it. But the engine was fine with the gas.
 
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