Symptoms of fuel going bad

I have some old 40% that did not want to start well, and blew a plug when running off a prime. Some 10% was a few years old and it ran well the one year and the next year the motor just would not start. They were both tightly capped in a dry basement. A model boat that I got at a swap meet had a tank of synth fuel in it. It sat for probably 5 years without running. The level just kept going down and there was just syrup left. Klotz. So I guess in that case the methanol and nitro just evaporated from the vent pressure line. So I can imagine it would not ignite well and run poorly until it is just pure oil. Then again there could be it picking up moisture. I did not use a lot of fuel years ago when running 1/2A and .15s. A gallon could last 3 years. Only the last 10 years that I use a bit more fuel because it is too windy here for the smaller slow planes.

I used to use a lot of methanol each week for about 3/4 of the year in dirt speedway. Only once had any problem with the methanol although it tended to get used very quickly and was often bought from a place that specialised in supplying racing fuel and the methanol was stored in big tanks underground and we had drums filled at the station. Other times I used drums of methanol that were pre-filled and distributed as such. Again, they never were kept by me for long. I did store them on a wooden shelf approx 2 feet off the ground and away from the wall. The only time I had a bad fuel incident was a night at the speedway where a number of us that bought fuel that night from the same distributors pumps had problems that seemed more than co-incidental. The fuel looked ok, colour was good etc. but a number of us had problems with engines not reving to peak properly.

The easiest way I now to identify a fuel based problem is to get some fuel from another source, run it in an engine, maybe a different engine, prove the fuel to be good, then run it in the engine having problems. The reverse can also be done by running an engine with known good fuel and then with the suspect fuel and see if the problem follows the fuel. The engine having problems may need the tank and engine and lines flushed to remove the problem dependent on what it is. Some additives eat neoprene type engine seals and it can cause various problems.

In 15 years of racing very high performance two stroke and four stroke engines, I can only say fuel ( Methanol ) was the cause once for me of engine problems ( I did also mix fuels and use additives such as toluene in AV gas not in Methanol ) and I dont really know why that fuel caused the problems that night. The distributor wouldnt say, and the fuel from same pumps was all ok a week later ( though in that time it could have been fixed. many rumours were afloat, but nothing more than rumours)

Maybe I was just lucky. I stored fuel as well as I thought was possible. Didnt let it age overly. Kept away from sunlight, used storage drums / containers as recommended by disrtibutor. Kept drums filled to the top, dated drums and used them such that none got old, or if they did, I knew how old. Both AV Gas and Methanol, plus storing Toluene. I disposed of fuel leftover in car or bike fuel tanks, flushed the fuel systems and engine after every race meeting, didnt keep small leftovers in drums. The same practices scale down to model engines as well.

Your luck / experiences may vary

Yabby

fredvon4 wrote:......
I personally buy cheap high nitro car fuel that has too low oil content and use my stash of nitro, methanol, and oils to mix for Cox engine performance
........

I've taken this approach since most airplane fuel is becoming increasingly more difficult to find, unless online. However, nitro anywhere close to my location is now unobtainium and methanol is becoming that way. I do use Klotz BeNol and Klotz Original Techniplate for oil sources.

Can anyone verify that Heet (yellow bottle) Gas Line Treatment is methanol and that it can be used as a fuel source?

a--

Hi All,
At -15C,
Castor oil congeles on inside of plastic jugs.
Mix well,
Have fun,
Good glow,
Dave

Of course I failed to adequately answer the original question

IMO all Cox small engines were designed to run BEST on 25 to 35% Nitro. Yes there are users who profess to successfully start and run on 0% nitro and even some who claim 100% synthetic oil is just fine

I have been patiently waiting Ken Cook to chime in as he (IMO) is our CEF GURU on this subject

That said, good fuel vs bad fuel is too subjective to really determine. You got good advise on how to determine via experimentation.

Scientific evaluation is not hard to set up and test:

Requires: Known good engine on Known fresh good fuel
The variables: Funky engine, Good engine, low Nitro fuel, high nitro fuel, old fuel, new fuel and sooner than later you have to accept that the permutations are too vast to seriously come to any perfect conclusion

Thus In the final analysis it is necessary to come to some compendium of past knowledge, and you did just that with asking on CEF

So a Lot of words to tell you. DEFINITIVLEY: Use your questionable fuel for test and cleaning only, do only FLY known good fuel as it will provide CONSISTANT engine runs

Advice: If interested in playing with Cox or other small internal combustion engines for the next many years---The buy bulk Nitro, Methanol, and appropriate Lubes to eventually mix or blend your own ....lots of folk right now can not conceive that a Gallon of ANY fuel is approaching or well over $40 per gallon

Contrast...I still have too many 2 stroke yard and lawn implements that require fuel ,,,pump gasoline has too much corn crap, store bought Gasoline with out any corn is $9+ per quart or $36 per gallon....So I have experimented with running my chain saws, weed eaters and leaf blowers on Nitro /Methanol based fuels.. with some success....Jest saying

Side note as I openly advocate making your own fuel

Point 1, most RC shops with Alcohol fuels pander to RC cars and not aircraft. I have found 35% nitro but only 17% oil gallons for $12~$19 many places

Torco on E-bay sell pure nitro for around $50 shipped

Methanol is usually available locally for between $2 and $15 per gallon ----look for local race tracks , cart, motocross, drag

A lot of companies sell Alcohol soluble oils: Castor is necessary IMO but there are many blends of synthetic and castor.

I have 2 gallons of Nitro. 2 gallons of Methanol, and about 1.5 gallons of various Castor and blended oils as well as a few pints of oil additives from Randy Smith

Using a 35% nitro /17% RC car racing fuel at $12 per gallon I can blend any variable I need for my small engines

HINT

I am an American tied to pints, quarts, and gallons...BUT I find Base ten mathematics too easy to not use...I do use the metric system for all my blending

Screw how many ozs are in a pint, quart, gallon...

1 Liter (like a quart) is 1000 milliliter.

Too simple: to make about a quart of fuel with 35% nitro, 22% oil 43 % Methanol the math is easy

35% of 1000 is 350 ML
22% of 100 is 220 ML
the reminder is 43% or 435 Methanol or 430 ML


Amazon is your friend for ML graduated beakers ....final hint