Paging 2-stroke gurus: premix

My 'crosser is a proper two-stroke one, not one of these new-fangled
thumpers. Sometimes I have a lot of mixed fuel left over and I may not
use it for two or more weeks.

I've often read that pre-mix degrades within a few days of mixing, so
should only be mixed a day or so before use.

According to one website, the problem is a reduction in octane rating
over time, but I'm sure I read somewhere that modern oils are octane
stabilized, but maybe the magic additives decay after mixing.

I've never had a problem, but being a worrier, I worry.

Anyone know whether there is a problem with using old-ish pre-mixed
fuel? I usually use Silkolene Super Mega Pro Expert Race Fully
Synthetic With Knobs On oil, BTW.

 

Pip Luscher says...

Only if you use something oddball like Castrol R or A747.

Petrol loses its octane rating over time, but months rather than weeks.
Oil should be octane neutral.

I wouldn't worry.

Not a couple a week old no.

 

Nah leave it in. I always do, never had a problem with it.

 

It was somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember Pip Luscher

The only problem I can see arising is if the premix is left for a couple
of years before use[1]. Or if you dump a couple of gallons into the tank
of a normal highish comp ratio 4stroke, you might get a bit of pinking.

[1] Although, there's so much shite in modern unleaded this advice is
worth what you paid for it.

--

Dave

GS 850 x2 / SE 6a
SbS#6 DIAABTCOD#16 APOSTLE#6 FUB#3
FUB KotL OSOS#12? UKRMMA#19 COSOC#10

 

I used Silkolene comp for years - with 2 or 3 weeks between some races.
Never had a problem mixing old and new fuel.

John

 

Not concerned about mixing fuel, just using old fuel. Yesterday, for
example, I had more than enough old fuel left over from three weeks
ago for a morning's play without having to mix up any fresh.

Everyone seems to agree (and my experience is) that it isn't a
problem. I just worry, is all.

 

Pip Luscher wrote in

I've had premix sitting in the shed for months between seasons. Never a
problem.

Good practice to shut the fuel tap and let the bike run until it cuts out.

The only problem I can see is from petrol evaporation if your storage
container does not have a good seal. Eventually the oil-petrol ratio would
change enough to affect proper combustion.