Thread: Unleaded fuel - going off?

From what I've read, the varnish/scale is more from additives in the fuel left after it has evaporated rather than the fuel itself.

Some people say fuel goes off, some say you can leave it in for years and not have any problems, I can't say I've ever had a problem!

I personally can't see any reason the actual fuel itself should go off - it sat in the earth for a few million years quite happily

Seano

We have the same problem with small engines that are not used often. I'm still trying to find an easy way to remove the varnishing

Tony

I had an 87 falcon (ULP) that was fitted with LPG only (no petrol) by the dealer before it was sold, in 2000 I drained about 20 Litres of ULP out of the tank, it had been there for 13 years and worked OK in my mower and ride on mower and the rest (14L) went into another car with no problems, the colour had faded a bit, but there was no odour or sludge, Regards Frank.

Modern petrol has a useable shelf-life of about three weeks, I've read. It's mostly got to do with the benzine, ethylene, xylene, etc they've added to replace the lead tetrate to make it compatible with ULP fuel systems (mainly catalysts).

In the Top End, there is a roaring trade in generators, mowers, etc every year due to our set growing season. They're laid up for months with fuel still in the system and everything gums up and dries out. When the grass begins to grow again, and the blackouts start, people go for the small engines and they won't work. Repairs always cost more than buying a new unit, so they dump the old one on the way to Bunnings...

It all makes a huge mockery of the "Reduce, Reuse, Recycle" line.

Dan.
69 2A 88" pet4, 74 3 109" pet4, 68 2B FC pet6.

Originally Posted by dandlandyman

Modern petrol has a useable shelf-life of about three weeks, I've read. It's mostly got to do with the benzine, ethylene, xylene, etc they've added to replace the lead tetrate to make it compatible with ULP fuel systems (mainly catalysts).

.

I've now read a few tests showing similar results. The fuel from 13 years ago would probably be better today than some sold 6 months ago.

It’s was always recommended that you fill the boat up with fuel on the way home each trip (theory was that condensation can’t form on the metal inside the tank if there is no air) but now pretty much everyone in the marine industry agrees that you get fuel on the way out, because it goes off so fast. F&B magazine did a very detailed story on this a couple months back - complete with lab results and a lot of scientific data.

I know that the Honda outboards (spec for Premium) run like crap if the fuel is more than 3-4 months old. If it hasn’t been out for a while Dad’s 150 vibrates and shakes all the way on the old tank, when it runs out and we switch to the 2nd tank that was filled that day it purrs like a fine sewing machine for the rest of the day… Like going from an old 2stroker to the hiTec EFI 4 stroke that it is, just by feeding it fresh fuel.

i was on a 4wd trip recently with a jackeroo on gas. They never used petrol just ran it 100% of the time on LPG. On a steep incline it got stuck and some of what was left in the tank started to dribble out from somewhere and it was exactly as you described.

first off the fuel seperates then the lighter stuff evaporates and leaves the rest behind.

the simple solution is to get bulk fuel in and run it then drain and replace the fuel.

when you finish with the vehicle drain the fuel tank and run it dry.

the best solution is to strip and hand clean every fuel system component then put it all backtogether.

once you get it all cleaned and running drain the fuel when your finished with it run it dry and then prime it up with something thats a single component hydrocarbon or as close as you can get (kero seems to work well for up to 6 months)

it wont run on it but it keeps all the seals and gaskets wet so they wont leak when you start out with new fuel again.

Dave & others....Thank for your input. Dave, I'm glad that you gave me the "simple" solution. I don't even want to know about the other one.
Draining the whole fuel system after each use is highly impractical but if it has to be done........

Did the old super petrol behave in the same manner? Sure it evaporated but did it leave all the crud behind to glue up carby parts?

I've contacted Caltex because they supplied the original bulk fuel in May 2007. They reckon that ULP has a shelf life of 12 months if stored under ideal conditions. The tanks of an F1 are not exactly ideal conditions.
Regards.
Bill w.