A backyard test for old fuel?

[FNQCairns]

Anyone have a way they trust to test for older fuel, like is it possible with today's fuels to tell a borderline use-able fuel from a fresh batch.

I have a jerry of older fuel + a jerry of 3 week old fuel, happy to use the 3 week old fuel but the other is evacuated fuel from the tank a while ago, 6 weeks + I forget how long it sat in the boat tank before evacuating it into the jerry.

Would like a way to discriminate between them if possible.

Cheers fnq

[PADDLES]

i can usually only guess/tell by smell, if it's gone off i reckon it has a turpentine smell, but if it's still good it should be real strong and make you recoil from it when you have a good whiff. i would think the 6 weeks plus stuff would still be ok if it's been kept cool and sealed. bit rough i know.

[Local_Guy]

paddles, have you been sniffing too much fuel.. lol.

fnq how much fuel are you talking about, if it's only a couple of Litres, save it for the lawnmower. otherwise mix it with new fuel and you should be right. you could always put it in your car. 6 weeks old shouldn't be too bad.

[Roo]

My car mechanic told me a test that the lads would do before filling up with premium fuel for a race meeting or track day was to half fill a Jam jar with a bit of fuel, put the cap on and shake.....if it was frothy and bubbly it was fresh... if it was flat like day old coke then tip it in but don't fill up, just pay the bill and find another servo.
I don't know if this is an urban myth or not but I have noticed most servos in the city have a notice about minimum fuel purchase now.

[griz066]

I have fuel in the boat that sits for 4 to 5 months at times between ski seasons, and there is not one difference in the boats performance.

[Roughasguts]

Not sure here but if you pour some in to a clear container the fresher fuel will be the clearer one. The older more yellow.

I use to use the smell test Yup it does smell like Kero, but that's the really old stuff over 12 months or more I reckon.

Now day's the fuel seems not to smell so bad as quick as it did 30 years ago.

[MarkDiver]

How about igniting a teaspoon full and seeing which one burns with a larger flame?? Seriously.

[backlash08]

to the best of my knowledge there is no acurate way without the appropriate lab equipement, fuel smell and appearance is created by dies and additives and these dont assit with the combustability performance, if your not sure, use it in the mower or older car - cheers - Craig

[iceknight]

at the work shop when i drain old fuel at owners request iv had fuel that is 12-24 months old, if no oil has been mixed. it goes in my car/ boat, and if his hugly old just a bottle of octane boost, saves them paying for dumping fees, and i tell them excatly what im going to do with it, but i guess then im at risk for gumming my own carbies, ect,

[Kleyny]

yep I'm with clee. Fuels have changed so much these days there would be no way to tell the octane rating unlessyou where in a lab.

Use it in your car or mower.

neil

[PADDLES]

trying to give up the sniffing local_guy

another question here (that's probably been covered somewhere else anyway) does the ecu in a modern electronic fuel injected 4s motor allow for the fuel to be of a lower ron and adjust it's settings to suit (ie. a form of anti-knock)?????

i ask this because i can leave fuel for a few months in my boat with a 140 sooz and she fires up and runs like a swiss watch with it anyway.

[jarrod]

FNQcairns, i used some old fuel(12+months)from a plastic portable tank to clean the old grease from trailer hubs when installing new bearings.Noticed that it had a definite black tinge through it.Dont know if this helps? cheers Brad

[trueblue]

I have fuel in the boat that sits for 4 to 5 months at times between ski seasons, and there is not one difference in the boats performance.

Is it a high tech new motor? I am guessing not if you have not had troubles.

I have witnessed pistons in brand new motors with the top melted out through use of old fuel in a high tech motor.

Up in NQ the mechanic had a bucket of old pistons, many with the same fault, from people using old and degraded fuel. Up there the fuel degrades much more quickly though.

[FNQCairns]

Thanks very much for the replies, the fuel in the jerrys is to be my 1/3 rule fuel for short trips so it most likely will go in on an almost empty tank so it's gotta be good enough, the engine is a traditional 2 st.

I ran out of time but I tried the sniff test back and forth, think I noticed a difference, then I put them in the sun for 20min and checked which gushed the most, both Jerrys have 20l in them, think the same one that got up my nose the most also had the most pressure release.

Ran out of time to do much more yesterday. Will take the spare empty jerry on today's trip with new fuel and do a couple of more tests in the next few days, shake ,burn and colour possibly, will save me hundreds of dollars a year if I can get to know the stuff + a little drama maybe. A test strip would be good, they can do every thing else

Anyway, Thanks again for the replies much appreciated, I am going fishing soon with all new fuel on board:)

cheers fnq

[gofishin]

FNQ, there is a way to gauge the quality via a density test – not as good as a ON (Octane Number) or full chemical analysis but better than the old sniff test. Don’t know if anyone wants to go to this trouble though...:-/

As memory goes...the lighter/more volatile components evaporate off first, followed by heavier ones etc, meaning the density of the remaining ‘petrol’ increases over time. As this occurs the ON actually increases, but this is not an indication of the quality of the remaining fuel. Now, petrol has a fair rate of thermal expansion too, hence the density changes with temperature so you would need to correlate the two to get any meaningful data. A temperature/density graph would be a great help if available off the net, however if not readily available a ½ dozen trials with fresh ULP at different temps should provide sufficient information.

Grab yourself:
1. a....thingy....(sorry, name escapes me – tall thin graduated glass measuring device that can accurately measure ~1L of fuel in a few or one ml increments). Must be tall and thin to provide accurate volumetric measurement.
2. accurate set of scales, to max ~3kg. i.e. postal scales
3. accurate digital thermometer with probe (readout to 1 DP, available from refrigeration equipment supply shops etc)

Put the ‘thingy’ on the scales & zero them. Pour in as much fuel as the graduations allow (or exactly 1 L) & accurately note ml & mass of fuel. Drop the probe in & note temp. Divide the mass by the volume & you’ve got the density at that temp. Compare to what it should be etc, or that what you have measured for fresh fuel.

Bit of a pain I know, but is a basic ‘scientific’ way to gauge quality via a density test. Maybe there are some Chemical Engineers on Ausfish that could help out with data etc, or provide a better way?
cheers

[Dory4.1]

Hi FNQ,

I wonder if a simple hydrometer used to measure SG of a battery would give you an indication of the condition of fuel?? Now, I'm not certain if this would work, but perhaps a comparison of some "known" old fuel to some fresh stuff might give you a guide, and a hydrometer from one of the auto shops should be fairly cheap. Once you know the variance between good and bad, you could make a call if you want to sue it or not. Any Thoughts?

Rgs
Michael

[gofishin]

Hi FNQ,
...simple hydrometer used to measure SG of a battery would give you an indication of the condition of fuel... Michael, same principle (density measurement) but unfortunately wouldn't work as an hydrometer is calibrated (volume & mass of float) for battery acid @~1.2kg/L, where ULP is ~ 0.76 kg/L. i.e. most or all of the float would be submerged/sunk. Good idea if you could get one calibrated to the right fluid density though.
cheers

[slyman]

just google fuel hydrometers........

http://www.stevenson-reeves.co.uk/hydrometers/LAOP.htm

[Dory4.1]

Cheers Guys,

With the price of fuel these days, if you regularily need to make a call on fuel quality, I'd imagine the cost of the right hydrometer would be recovered fairly quickly.

Rgs
Michael

[FNQCairns]

Great lateral thinking Dory4.1! Thanks much for the idea, just googled it myself too, expensive yes, but cheaper than the alternative, it's just a bloody good idea! With the price of fuel almost equalling the jerry can it's in I would be silly no to.

cheers fnq

[finding_time]

Fnq is do so much thanking i think i'll just type this and see if i can score a thanks!!!

[FNQCairns]

Fnq is do so much thanking i think i'll just type this and see if i can score a thanks!!!

:dankk2:ft ,but only until tomorrow then I am taking it back;D;D;D

cheers fnq

[finding_time]

Now you might feel gulity if ya do!

[gofishin]

Good link Simon.

FNQ there may also be another option and that is a Handheld Refractometer, which uses the refractive index of light to measure the density of a liquid. Probably more expensive again, but would be a lot more robust. Accuracy vs a hydrometer would be comparable I guess - depending on the instruments ($). We use them with glycol/brine solutions, but would also be available for petrol. They also come in fully automatic digital and combination versions, but then you may need to sell your outboard to pay for one...then i suppose you wouldn't need it anyway...;D.

Let us know how it all works out & what results you get.
cheers