Just thought someone may be interested in this
i scrapped a car that had been sat around for a good year but took the petrol out prior to it going
for emergancy uses :-) (as you do) ok im from yorkshire
anyway
put this petrol in a car as it was showing zilch and then did a co test prior to it going for an mot
guess what?
i couldnt get it to pass
co was way high
so was the hydrocarbons
put some fresh petrol to mix with the old stuff
got it down in no time
now the thing is
why was the co high?
was it the petrol
or was it just that the catalyst needed lighting up?
|
|
Unleaded fuel suffers form oxidization effects as any gardener using 2 stroke fuel in strimmers and the like will tell you. Last years fuel kept through the winter is fairly useless. It just burns a lot slower and completely fools a 4 stroke engine and its emissions system. Regards Peter
|
I have a two-stroke lawn mower (Flymo) and have never noticed any deterioration in fuel quality, even over the winter months.
The fuel when neat is kept in a steel can and when mixed with oil, in a plastic measuring bottle.
|
|
|
|
I'm not a chemist, but I suspect that the variable volatility of various additives would have altered the composition over the year, thus affecting the burn. Old petrol is not considered ideal.
Mind you, as you imply, it also depends how warm the engine was before the first test. I understand that diesels fare better for emissions tests after an Italian tune-up to blow out all the crud, which does rather defeat the object, of course...
|
What I think may have happened, as JBJ has suggested is that the more voltatile components of the fuel are long gone.
The fuel will originally have been composed of a mixture of hydrocarbons - the more volatile among them will also tend to be the ones with fewer carbon atoms - so for alkanes, C5 H12 will evaporate off faster than C8 H18, for example. So, in blunt terms, there will be much more "C" being metered by the fuel supply system - the effective mixture will be way rich - hence the high CO.
Also, the heavy - heavy fuel, will burn less readily, and may only partially burn, hence the high HCs.
Number_Cruncher
|
OK BB now can you explain that to me?
I shouldn't post after coming back from the pub, but it was eurovision!
|
thanks everyone
so basically, dont use old fuel in a car prior to mot, but flog it to the off road moped muppets in future.
;-)
|
|
|
|
Also the heavy - heavy fuel will burn less readily and may only partially burn hence the high HCs.
Your ugly big car might not even climb that hill. ;o)
|
>>Your ugly big car might not even climb that hill. ;o)
But, it's ideal if you wanna run cool!!
|
The variable quality of old fuel probably depends on how much opportunity it has to oxidise or lose volatile components.
Obviously a few gallons sitting in a large vented tank will suffer most, but petrol in a full sealed can probably very little. I too have never noticed any adverse effects from old petrol in strimmers etc, but then I deliberately fill them up before storing for the winter. I find the gunging effect in a dry carburettor much worse than any alleged loss of volatiles from a full tank.
|
I have a 2 stroke petrol strimmer that normally only starts after I have totally exhausted myself, and threatened to throw it in the bin several times.
Having recently got into boating, i was told always to use fresh fuel.
I tried fresh fuel and 2 stroke mix in the strimmer, and bingo, two pulls and it was off! knock me down with a feather.
This is a repeatable event, so whatever the reason, fresh fuel is best
|
You notice it in the bike if it's laid up for a few months. Apart from being reluctant to start, the engine feels generally sluggish and lumpy until the tank is filled with fresh fuel. After a mile or so on the new fuel, as the fresh stuff starts to replace the old stuff in the carb float bowls, the engine noticeably "smooths out" and normal performance is restored.
Optimax / V-Power is much, much better after a lay up period than regular 95RON Unleaded, I presume because the better additive package prevents the fuel from going off so quickly.
Cheers
DP
|
|
Frost do a fuel preservative which works well (I've got some 3-year old petrol which still works OK and doesn't smell stale). About £10 for a bottle which lasts ages; perfect for little-used bikes, strimmers etc. I think Yamaha dealers also sell something similar.
|
Frost do a fuel preservative
Forgot to say ... the reason I use it is because it stops the clogged jets in the carbs which I used to get over the winter.
|
|
|
|
