was a bit bored today and got a little bit of nitro for my rc car and poured about 20 - 30 mls on the work bench and got it going with the help of my lighter and i found that it burnt without any visible smoke, so i did another test but with unleaded roughly same amount it burnt with a s**t of black smoke that was obviously clearly visible, the fuel for the rc is 10% nitromethane 20% castor oil and 70% methanol now i know methanol is 49% oxygen or there abouts any way and i thought that was why the mix burnt with all but no smoke but then i remembered the castor oil which i thought would make it smoke a bit but no. i thought this was a real mind boggler any one got any ideas why the unleaded burns with smoke and the nitro mix without

i might try mixing a small amount of the 2 tomorow

welll u cant really test it open

as both engines burn the fuel under compression

when my rc car is running it pours out smoke something cruel

this is the castor oil bieng burt off

ou do not want to put 2 stroke petrol in a car!

ost extremely light fuels burn with no smoke, like metho spirits, white spirits, methanol and the like. But ULP has more in it than just the base hydrocarbon fuel, it has additives in it, but what exactly i don't know.
Here is something that i have noticed over the years.
Go to the servo, get some ULP in a tin, go home and wash a greasey wheel bearing....washes good and quick.
Leave the fuel in the tin, with lid on of corse, for about 2mths, then wash another greasey bearing, and it is slower to get it clean.
I have been told that ULP is only good for about 3 wks, after that is goes down hill.

Urgh! Might drain the 8 month old fuel out of the tank in my car then haha.

Was thinking i should do the same to teh 4 month old tank of pulp in the blue car lol
Brett

hmm interesting

Makes sense, so imo it all comes down to vapour. seeing as when fuel is set alight it is not actually the liquid which is burning it is the vapour (gas) released from the liquid which burns. So it makes sense that over time though evaporation that vapour/gas will disperse to the point where there is a lack of flammable material to be burnt off. Hence leaving a rather low volatile fuel in the tank of the car if it has been sitting for an extended period of time. Although modern day cars with there extremely well sealed fuel system would help prevent this, the purging of the system to help prevent the hydrocarbon build up would not help the long term storage of the fuel.
And yes asaik fuel has a very short shelf life and why i believe i have been told to always buy the "higher" octane fuels from the busier servo's. As they have a higher turn around rate than say the small independent that only get his premium tank filled once a month because no one buys it from there so their fuel is older.

old fuels are very different to the fuels of today.. Between the addatives, detergents and everything else they put in the fuels the shelf life is dramatically reduced.

The '79 Firebird has been sitting in my grandads back yard for about 20 years.

The Bedford has been sitting in my grandads backyard for 2 years.

The firebird started straight away.
The bedford cannot be started on petrol, only gas. And it has Ultimate 98 in it.

Petrol of today turns first to the thickness of honey, then it goes solid.
When you scoop/scrape out bad fuel it stinks..

If you're going to let fuel sit, I recommend putting in some fresh fuel periodically, or just drain the tank and put fuel in as you need it..

fuel does go stale but without knowing its batch history its an unknown value. different cars will also handle bad fuels differently.