Fuel (Petrol) how old is too old?

[The_Hawk]

When is fuel considered too old? and what can you do about it?

In my case I drive my car very few kilometers *most* of the time. There is the occasional interstate run but primarily it's a ride to the train station in the morning. Christmas is also a very quiet time since I'm off work on holidays and not even doing the station runs. The family don't all fit in my car so we are out and about with the van and my poor little beast sits there all sad and lonely.

On checking my records (fuelly) the last time I filled up was December 21... and I still have a tank of juice left now.

So... how long is too long? Does 6 - 8 weeks between fillups matter?

Should I start just putting in $20 at a time and not filling it so it gets better turn over?
(this will hurt my brain since I was always taught to fill up at the 1/4 mark and have always filled the tank)

Is there a third alternative I'm not aware of?

[h100vw]

When is fuel considered too old? and what can you do about it?

In my case I drive my car very few kilometers *most* of the time. There is the occasional interstate run but primarily it's a ride to the train station in the morning. Christmas is also a very quiet time since I'm off work on holidays and not even doing the station runs. The family don't all fit in my car so we are out and about with the van and my poor little beast sits there all sad and lonely.

On checking my records (fuelly) the last time I filled up was December 21... and I still have a tank of juice left now.

So... how long is too long? Does 6 - 8 weeks between fillups matter?

Should I start just putting in $20 at a time and not filling it so it gets better turn over?
(this will hurt my brain since I was always taught to fill up at the 1/4 mark and have always filled the tank)

Is there a third alternative I'm not aware of?

I notice when logging cars after tuning that old fuel will sometime cause timing to be pulled. Often it's folk that have been using 95 ( duh) others it's because it's been in there weeks, for similar reasons to your self.

If you wanted to know if it's any good. Log the timing pull now, with the old stuff in and see what it does.

Personally, as I do 5-600 a week most weeks, I don't worry and just fill up but when one car has been idle for a couple of weeks, I'll run it down deliberately.

I think if I were you I wouldn't leave it in that long.

The 1/4 tank rule is BS in my eyes, if there's any crap in your tank, it's going to migrate to the lowest point, which is where the pick up is anyway. In the olden days of rusty old steel tanks there was some credibility to it but even MK2s had plastic tanks.

It's why we have fuel filters

Put in what you will use in 2-3 weeks.

Gavin

[Transporter]

The water that accumulates in the fuel tank will get easily through the filters and will cause the damage to the fuel system (injectors, fuel pressure regulator, fuel pumps), so for that reason I like to keep the fuel tank full. Because less air in the tank means less surface area for the condensation to form. Using good fuel additive that safely breaks down the water is very important in theses cars that do low mileage/short trips.

The best would be to contact fuel company and ask them what's the life of their fuel once it gets in the car's fuel tank?

My guess is that it will be anything between 1-3 months.

[golfmeup]

Off topic slightly - Gavin, would you recommend draining a tank of a car that has been sitting for 6 months.
Or just fill it up with fresh 95 and drive on, letting it mix with the old fuel?

I can't remember how much fuel is in the tank, but would be now more than 1/4.

[Diesel_vert]

BP states that petrol in vehicle fuel tanks will keep for 3 weeks @ 20°C (or 6 months if in a sealed container).

For more information, I refer you to this link: BP Fuel Topics

[h100vw]

Off topic slightly - Gavin, would you recommend draining a tank of a car that has been sitting for 6 months.
Or just fill it up with fresh 95 and drive on, letting it mix with the old fuel?

I can't remember how much fuel is in the tank, but would be now more than 1/4.

Unless you plan on cutting a lot of grass, I'd just fill it up and drive it. Definitely do a decent length trip though. Brissy and back or a couple of hundred Km out the back of the hinterland.

Stihl don't recommend using old fuel in my whipper snipper, I always tip it back into the can when I am done. So I can shake it up and mix the oil again.

Not so convinced there'll be enough condensation present, to become a problem. Old MK1s and rotten filler necks were a big drama in my past but not since 1993.

They are practically sealed from a fumes point of view. I worry about it in aircraft, as water will freeze in the fuel system of an aircraft, a known crasher of aircraft. Also, there's algae that grow in the tanks too which is a problem for aircraft over time.

[The_Hawk]

BP states that petrol in vehicle fuel tanks will keep for 3 weeks @ 20°C (or 6 months if in a sealed container).

For more information, I refer you to this link: BP Fuel Topics

Very interesting reading:

http://www.bp.com/retail/liveassets/bp_internet/retail_new/retail_new_australia/STAGING/local_assets/downloads_pdfs/0_999/Petrol_Life_in_vehicle_tanksv4.pdf

The points for maintaining fuel in equipment is interesting. When it comes to mowers or whipper snippers and boat engines it’s relatively easy to follow those points and I assume it has more impact on these types of simple (read no ECU) engines.

But for a car, surely many people have fuel for more than a week sitting in a car and it’s not always possible or practical to add more fuel… especially when you have to start the thing up to drive to the servo… of course adding a little each week rather than a lot once a month is probably the better option.

From what I read and especially for our small capacity, forced induction engines the “loss of light components” is not a good thing.

Loss of light components – impact on octane
The light components in petrol are lost first as the petrol sits in the fuel tanks. These
components provide valuable octane benefits under high revving conditions such as
cold start acceleration and the loss of these components can result in detonation and
pre ignition at high speed resulting in piston damage.
The remaining components that have not evaporated are high octane and octane can
actually increase with time but this octane is not available for high revving
conditions.

Although I’m interested in just how detrimental it is to a modern vehicle?