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2 cars in the household. 1 is getting minimal use (weekly 5 mile round trip to supermarket). The other hasn't moved for 5 weeks and looks set to stay that way. It has a full tank of petrol.
How long until that becomes a problem?
I know we can rotate them, but even so a full tank of fuel lasts about 550 miles, so just over 2 years at the current mileage! Lockdown should be over before then (hopefully!), but any facts associated with long term storage of petrol in a car fuel tank?
More likely to have battery problems, lots to run down batteries now and can take 20 miles of driving to replace a start up in the battery.
Fuel, in a normal car with normal fuel, especially if full, we’ve not had a problem with 9-12 months, officially it’s 3 months ish. Tow aspects are taking on/absorbing water (and or comes from condensation) and fuel breaking down / going off.
Our experience: old cars with one year old plus fuel, no issue, old bike with one year old plus fuel no issue. Newer cars, longest we’ve left one was 9 months, still no issue. Aeroplanes left well over a year, no problem but their fuel is much better and therefore takes much longer to break down. On the other hand, race car is unhappy when expensive pump fuels are more than 3 months old, race bike won’t start with three month old fuel!
Normal cars Ok but it will be battery that might cause an issue. We use ctek chargers and one some the little indicators. We leave handbrakes off. Open windows, doors for an hour on nice dry days, maybe once a month. I check tyres are staying inflated.
With the quantity of fuel in a petrol tank, you are talking years before it will be a big problem I reckon. The "going off" problem is more associated with lawnmowers/chainsaws holding about about 1/4 litre
Petrol should last months (6 typically) and then the only issue after that would be a slight loss of performance.
So nothing to worry about on that front.
Blimey Rusty, the fuel will have definitely gone off before I reach the end of that video! They are a BMW 5 series and X1, both 2019, so not 'classic cars' by any stretch.
Yep, that was my initial concern welshfarmer. I am fairly rigorous with emptying lawn mower, chainsaw, strimmer, hedge cutter, leaf blower etc before each winter.
Guess a start up every week or so to keep the battery healthy might be a good move.
I regularly leave about about 50L in our boat tank (tank takes 320L) over winter from September until may/June.
The engine is a 225hp V6 and I've not had a problem yet.
Carb'd engines have more of an issue if the fuel in the carb evaporates leaving a gum that blocks the jets.
Both those cars will have knock sensors and will adjust spark timing and fuel ratio for best operation. A full tank will be fine for ages.
Just before the COVID lockdown I got one of my cars out of the garage after leaving it there for the winter. Started fine and ran fine (modern fuel injected). As others say it’s the battery condition that will be more of a problem.
Starting it up weekly for a short idle probably won't do the battery or the engine/oil any favours. When I had to leave my van for a number of weeks I plonked a solar panel on the dash and it trickle charged the battery through the lighter, it also came with croc clips for cars without a live lighter with the keys out. If you have power near a battery conditioner would be even better.
Fuel will be fine.
Battery might be knacked though.
It'll be fine. I've got a fun car with a notoriously fragile engine that I often leave for a year or so with fuel in it. It will always drive fine on a restart providing I take it easy. (NB the bugger had never restarted first time, but that's never been due to the fuel quality...)
As above, anything remotely modern will just use the knock sensor and knock back the timing at the very least. It'll be fine.
Fuel is very cheap at the minute though, worth just leaving your car idling to burn it off and buying some more cheap fuel !
Fuel is very cheap at the minute though, worth just leaving your car idling to burn it off and buying some more cheap fuel !
Aye. Get that cleaner than it's ever been in living memory air dirty again.
For no reason what so ever other than fuel is cheap.
The issue of fuel going *off* is massively exaggerated. Yes I wouldn't have fuel that is years old if I was fault finding but on something that runs I regularly use fuel that's over a year old as I buy 20l Jerry cans of fuel for the garden tools -i often leave the generator full one year to the next and it runs just fine
On the battery front, is one of those solar dashboard trickle chargers worth getting?
^ what trail_rat said
Im loving the fact that my car has used 1/8th tank in 6weeks.
And my average speed on the computer is 10mph higher than when battling with busy roads.
Mpg is up about 7/8 as well due to lack of stop start.
Left a Hyundai i10 with half a tank full for a year after dad passed away, it was fine. Battery needed charging though.
I think the stated time is about 6 weeks. But it depends on the car.
Petrol - leave the tank as empty as possible and fill up with fresh when needed.
Diesel - leave tank as full as possible to inhibit condensation and subsequent bacteria problems.
Just get a cheap battery charger and put it on when you remember.
I put a tenner in a few weeks ago, but TBH Im still doing about my average one trip a fortnight in it. New years resolution was to not drive unless I have to which pretty much just mean the tip and a few trips to see my parents, and cant do that anymore !
The petrol in my land rover is almost 4 years old (it normally runs on gas, petrol used only for the night heater).
It still ran on petrol last time I tried, which was about 6 months ago. Granted a low compression rover v8 isn't exactly fussy, but the petrol still seemed to do the whole exploding at the right time thing.
On the battery front, is one of those solar dashboard trickle chargers worth getting?
I've never found them useful given the UK's relative lack of sunshine, plus it's not entirely clear if they work through glass anyway. I've tried a couple and they were both essentially useless.
You're better of with one the small C-Tek trickle chargers if you can rig one up - I have a long extension lead so all the charging gubbins are safely inside the house with no exposed plugs etc. You can wire a socket to the battery to make connection and disconnection easy.
It just loses a little of its octane value as it ages. Contrary to popular belief this isn't anything to do with the petrol's calorific value but its knock resistance. If you have a turbo car or other performance car then just don't floor it with 'old' petrol.
Petrol – leave the tank as empty as possible and fill up with fresh when needed.
Fwiw - and I don't know which is the correct answer - the video from Evo bloke embedded above actually suggests that filling the tank completely reduces the surface area of petrol affected by oxidation and, presumably, the proportion of oxidised petrol overall.
I have no idea who is correct, but my experience is that petrol doesn't, in real life, degrade to the point where it stops working even after a year or so of sitting.
Regularly leave the fun car in the garage for 6 months over the winter and it's absolutely fine. If we aren't out of lockdown by the time your fuel goes off we'll have much bigger things to worry about.
Isn't it the increased amounts of ethanol in modern petrol which shortens it's shelf life? I have a couple of 20L jerrycans I use to fill a ride on mower, push mower, brush cutter and hedge trimmer. I used to have issues I put down to bad fuel until I started using fuel stabiliser. It claims to increase fuel life from a few months to 2 years. It's fairly expensive though so not practical for the car.
For the battery, I have an Optimate intelligent battery conditioner/charger I bought for the motorbike. I use this on mine and my wife's cars too. Overnight once every fortnight or so seems to keep the batteries tip top.
Re diesel, there's a fungus or bacteria that grows in the tank, isn't there? Might put some diesel fungicide in mine. It's not moved for about 4 weeks now. Battery was 12.5V after the first three weeks so I guess my previous battery drain issue has been solved - yay!
Battery is disconnected now.
Normal cars, [petrol] fuel left 12-18 months probably be fine. The fuel systems are generally unvented which means light ends are unlikely to fizz off, also if it's kept out of the sun it's not going to get too hot. Possible issues are filling up with winter fuel and then using during a hot summer, ther is potnetial for vapour lock to occure, but it's generally extreme circumstances.
Ethanol in fuel can be an issue, but unliklely again. Ethanol is hydrophoboc, so pulls in water, but new vehicles will unlily have any way of this getting to the tank/fuel lines.
Gum formation can happen even without evaportion, it generlaly comes from high addmixtures in fuels, but is also from other contaminants, small amounts of heavy oils (this is where your lawn-mower/chainsaw issues come from). Detergents in fuels will clean a lot of these gums up in operation, of valves and injectors, but not whilst idle.
Diesel, has other issues with Bio (FAME) being included. It can be a breeding ground (that and water) for microbial growth and is more likely to cause precipitates. The cetane value will not change, so initial ignition characteristics do not change. With regards to volatility characteristics, the opposite of Petrol is observed with diesle. Summer diesel has a cold flow properties that can be an issue durign the winter due to wax formations blocking filters. So filling in summer and using in winter can be an issue, but not the other way round. - Caveat its relatively extreme and more of an issue in scandic and northern europe.
Fwiw – and I don’t know which is the correct answer – the video from Evo bloke embedded above actually suggests that filling the tank completely reduces the surface area of petrol affected by oxidation and, presumably, the proportion of oxidised petrol overall.
I have no idea who is correct, but my experience is that petrol doesn’t, in real life, degrade to the point where it stops working even after a year or so of sitting.
It probably depends on whether your plan is to do the best thing for the car or prep for the zombie apocalypse.
My opinion is that I only need enough in the tank to get to a petrol station, then I can get fresh petrol. So why worry about whether a full tank lasts 6 weeks, 6 months or 6 years with only 'some' degradation when you can have fresh petrol and zero issues. Absolute worst case we're locked down for 18 months+, no ones car's start and we all have to walk a mile to the nearest garage with a can.
If you're anticipating needing a 500mile range and petrol shortages then the answer is probably that a full tank will keep better than an empty one, but you've still got to use that tank of petrol at some point and your car may or may not be happy with it.
My experience is the midget runs like it has a bag of spanners in the sump in the spring when running on last summers petrol. But that's probably down to multiple factors, off petrol, deposits in the jets, there always seems to be at least one seal/pipe/diaphragm that's been killed by modern fuel, etc.
Does the UK actually have winter and summer fuel mixture for sale in petrol stations?
I'm not sure if winter petrol is still a thing.
It certainly used to be, more shorter chain hydrocarbons helped with cold starting.
Not sure if its still a consideration with modern engines
rydster
Member
Does the UK actually have winter and summer fuel mixture for sale in petrol stations?
very much so. the major difference is the vapour pressure. Typical UK summer is around 50-60kpa, whereas ive seen some winters with 80-90kpa. There are different ways you can get these changes, some are by butane additions, which is a by product of refining process or by using other "fizzy" streams or running the units differerntly.
the differences on the conitnetent (north) are higher, with some being as high as 120.
I'd be more worried about rear calipers seizing up from the handbrake being left on. Flat-spotted tyres if you leave it sat for too long. And interior dampness and mould if the car's left sitting with dampness inside. And the battery obviously. And mice chewing through your electrics and nesting in the engine bay 🙂
I was waiting for Sui to chime in!
My experience is also cars (modern) fine, lawnmower not yet been a problem but I try to run it empty for winter, chainsaws I've never had trouble but do always run to empty and use a stabilizer. If I were close to an airfield I'd enquire about E free for the saws.
Isn't mcmoonter on 4+ years?
Might be diesel.
On the battery front, is one of those solar dashboard trickle chargers worth getting?
In my experience on a small car that gets left for months at a time - yes, but only if the battery is in good nick to start with. If you want to use the lighter socket you need to check this is always live with the ignition off, it is on my polo but wasn't on my yaris. Mine has been sitting outside since new year this year due to the current travel issues so I think the rear brakes will be quite funky by the time I finally get back to it, poor old thing.
Fill the tank up, get an intelligent charger. Simples.
We have a “summer car” that does about 50 miles a month unless the sun is out and that is only because I take it to work for a run out, we always fill it up when it needs petrol and have never had a problem, it’s been sat for a couple of months on a number of occasions without any problems.