how long for gas to gum up or turn to varnish?

[vortec]

my k5 has been sitting for several months, waiting for a decent remanned 350. now that the old job is history and the new one is going well, i can spend the money. but, i've never had gas sitting that long, so i don't know where i stand on gas condition. should i:

1. drop, drain and clean the tank (probably, but i sure hope not)
2. run it as-is (probably not)
3. use a pour-in product to dissolve gunk, and maybe add another inline filter for a while (would love this option, but doubtful)
4. other ideas

i know old leaded gas got nasty fast, but i was syphoning and using this unleaded after as much as 4 months. been quite a bit longer now, though.

 

[Jishory]

when i did an engine swap my truck sat for 4 months, when i did the manual swap i think it sat even longer, the gas was fine both times, i would fill it the rest of the way with fresh gas to dissolve anything going on in there and call it a day... how long has it been sitting exactly?

 

[mechted]

gas will go "stale" over a couple months, but not solid, ive had my K5 sitting months and months without starting and havent had any issues
just refill with fresh stuff to dilute out the stale gas and you should be fine

 

[4xcrazy]

I have a car in the back yard that has been sitting for the past year, just went out there the other day, cleaned everything up, fought it a bit, and it fired up and idles,,,not the best idle in the world, but i blame this on the gas, could probably use alittle more octane in it.

same as above, but i would also add some of the stuff that helps remove moisture from the fuel, condensation and such.

 

[vortec]

thanks for the responses. to answer how long, it's been 7 or 8 months, at this point. my pickup and the lawn mower ran fine on the gas after 4 months. i just wasn't sure about 8 months. i've never let it sit in a vehicle that long. certainly didn't intend to this time. i guess i'll just try fresh gas and some mmo. it will still be a little longer, since we had a nasty (by texas standards) freeze come in this week. knuckle bashing at 25 degrees in the rain is not fun at all.

 

[diesel4me]

jello!...

I've had gas turn to jelly in 3 months in lawnmowers here before..yet I have not driven my 81 G10 since dec 03,and it started right up and ran a bit ragged,but it smoothed right out,after I added a few gallons of fresh gas.I was suprised the carb wasn't gummed up or dried out..the accelerator pump didn't squirt so good the first time I ran it,but it did seem to revive itself after I let it run a half hour..I've only started it about 3 or 4 times the past 2 years..I shudder to think whats in the gas tank now..probably ICE!..I let it run OUT of gas the last time..


I'd say after 6 months or a year,adding fresh gas might not work..if you add marvel mystery oil to the gas,it supposedly prevents it from turning varnishy..seems to work in my lawn and garden stuff I put it in...they sell "Stabil" stuff that helps too,but "oxogenated" gas gets "stale" much faster than the old stuff,and even all the additives seem to have limited success at preventing it from going sour..

 

[rjfguitar]

It should be fine, 8 months isn't that long. I have gas that has been in my K5 for almost 9 months. Yesterday I drove it down the street and back and ran exactly how it did when I left the gas station 9 months ago.

I have snowmobiles that sit all summer and hold the same gas for 6 months. They run just fine in the first fall trip as they did on the last spring ride and have never had a problem with dirty carbs.

Get your new engine in, get it running on the gas that's in it, and go put some gas in it.