[SOLVED] petrol ageing ? Solved

It's just one of many things that may make a machine difficult to start at the start of a new season. Old petrol isn't as good as new petrol but it's not so bad you should throw it away IMHO. If nothing else you could put it into your car (if you have a petrol fuelled car) and thus not waste it.

It's maybe worth draining any little dribble left in the garden machine's tank that has been left for several months though I've never bothered, just fill up with fresh petrol and the dregs will be diluted enough not to cause problems.

Really. Oxygen from the air reacts with it and heat and humidity can cause it to degrade. The longer the exposure to these factors, the worse the possible problems. Ideally, you should not store petrol for more than a couple of months, particularly in hot weather.

Possible problems that can arise are:

Loss of evaporative power and changes to ignition temperatures, both of which can make the engine more difficult to start

Lowered octane rating, which can result in knocking.

Higher resin content, which form unwanted deposits

The formation of peroxides, which corrode metal and eat away at rubber.

Higher ash formation, resulting in coking

High water content can cause emulsions to form or encourage microbial growth, both of which block filters. Reduced lubrication properties which can increase wear in the fuel pump.

Bio-components in the fuel can make some of these problems worse in long-term storage.

All perfectly valid points, but I am too mean to do that. Drain it into another container, start the season with "fresh", and blend the old stuff back in over a couple of tanks, discarding the last bit to exclude any moisture, solids, or bio-sludge. You should be able to see this if you use an intermediate container (like a glass or white plastic jug).

Whilst all the above might be true, my lawn mower starts every spring with the old fuel in the tank and has never had a carburettor clean/strip in 30 years.

Tim

My 4-stroke engines have no problem with older petrol - most (but Not all) of the 2-strokes are happier with fresh(er) petrol. I'd never keep mixed 2-stroke fuel until the next season though.

Is it an old Suffolk Punch? That was my experience with ours, the only thing that prevented it from running was stcuk valves, just take the head off and unstick them and all was well again! :-)

B&S petrol engines are much the same, very difficult to prevent them from starting.

I think it was four years while the house was being rebuilt that left my

My strimmer ran dry and that did fail - but not from stale petrol, but from a dried out fuel filter.

In general I think you are safe for about 2 years in a sealed tank or can: but you may need to add some new mix for the first start/. Of course E10 may change all this

Well in my case there never is a 'next season' foir 2-stroke as the chainsaw tends to be in use right up to the winter and the hedge trimmer is alive early in the spring

I've just come to the end of the 20l can I filled up last summer for my ride-on lawn mower. I hadn't found any problems

It happens that fred formulated :

I would suggest that is rubbish. I have never had an issue with either

The guy's just trying to impress you.

For 4-stroke, it just isn't so.

For 2-stroke, "stale fuel" is insignificant when compared to the other issues that can cause problems.

Just don't make a 2T mix with snake oil !

PA

I was assured by the company who serviced my Mountfield that was why the engine was not running properly. Turned out to be a faulty coil.

I always run my engines out of petrol at the end of the season. The petrol in my sealed cans works fine the next year.

In my experience yes.

Bill

One thing that does seem to make a difference is storing petrol in a steel jerrycan rather than a plastic container. The volatile components in petrol do seem to be able to diffuse through plastics. A 10 litre jerrycan is more convenient for mowers than a full size one and still seems to last me for a couple of years. John

It does age as it evaporates and the octane reading drops of course, but how soon it does this often depends on the temperatures its stored at. Brian

I agree all points. I have many small engined tools that often don't get started yea on year but have no problems from old fuel so far, E10 may change things.