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Lubricating oils

Oils whose primary use is for lubrication.

Machine oil

Machine oils are a class of thin light petroleum oils used for undemanding lubrication, such as small machinery, hand tools etc. They are also widely used to thinly coat steel tools before export, preventing rust.

Sewing machines and many other appliances use machine oil.

Some machine oils are edible, such as for use on food processing equipment, some are not.

Baby oil

Baby oil is a higly refined petroleum oil, much like a food grade machine oil, with a little mild perfume added. Its a very convenient way to buy a machine oil for many DIYers. (The method of its extraction from babies remains a closely guarded secret.)

Engine oil

Engine oils are excellent lubricants. They are highly stable petroleum derived oils, with additives to enhance their stability even further.

20/50 was once the most common engine oil grade, but 10/30 took over as the dominant grade a couple of decades ago. 10/30 is less viscous, and pumping it uses less energy. Engine oils are much more viscous than machine oils.

Used engine oil

Used engine oil is blackened by engine deposits and assorted burnt matter. It still lubricates, but there is potential for toxicity of a contaminant. Used oil is also believed to be carcinogenic to some degree, and garage staff are advised to use gloves when changing oil. These issues plus its gross dirtiness make it very unpopular for DIY use.

50/50 used engine oil plus paraffin or diesel has long been used to preserve exterior woodwork. Its effective and cheap, but dark in colour and the engine contaminants are an issue. New oil and paraffin/diesel is a better alternative, with neither of these issues.

Used or new engine oil can be used for steel hardening.

Castor oil

Castor oil was the original engine oil, and the source of the name Castrol. Its still available for historic vehicles designed to use it. Its a fixed grade of oil, unlike today's multigrades, hence its viscosity varies more with temperature. Its much more prone to gumming than modern engine oils, and is not suitable for today's engines.

Gear oil

Gear oils are designed to survive higher shear forces than engine oils. Engine oil is not recommended for gearboxes (with the exception of the original Mini)

2 stroke oil

Another petroleum lubricating oil.

Silicone oil

Silcone oils are much more expensive than other (carbon based) oils. They have little DIY use, but are used occasionally. They're used as lubricants and as DOT5 brake fluid.

Silicone oils

  • insulate well electrically
  • conduct thermally.
  • are not flammable
  • don't degrade rubber compounds
  • remain stable at high temperatures (over 200C)

DOT5 brake fluid is incompatible with DOT2,3 and 4 fluids, and not suitable for use in systems not designed for DOT5. Note that DOT 5.1 fluids may not be silicone.

Silicone oils are also found in anti-flatulence products, though this is possibly more 'don't do it yourself' than DIY.

Fuel oils

Oils primarily used as fuels

Diesel, 35 second oil

Red diesel and 35 second oil are the same product.

  • Also known as gas oil.

Red diesel is only legal for non-road uses.

Its occasionally used as heating oil for old installations. 35 and 28 second oils aren't interchangeable, 35 second requires a larger burner jet and causes more heat exchanger fouling.

Red diesel has 2 markers, one visible (red), one not. These stain filters.

Diesel filled tankers are labelled UN1202.

Despite being a petroleum fuel, diesel is not highly flammable. Applying a naked flame to a pool of diesel is unlikely to light it.


Best known as a fuel for heating & old blowlamps, paraffin has several other uses too:

  • mix with oil to make a penetrating oil
  • engine oil flushing additive
  • cleaner especially effective for all types of vehicle & road dirts, oils, tars, bitumen, etc
  • insect repellant

Paraffin can be used neat for cleaning car parts, or it can be mixed with water & a detergent.

Paraffin is now also known as:

  • premium kerosene
  • kerosene C1
  • premium burning oil (PBO)

Paraffin has been dyed with several different colours over time, including blue, pink, yellow, green.

Heating oil, 28 second oil


  • 28 second heating oil,
  • kerosene
  • kerosene C2
  • Tankers are labelled UN1223

Widely used for central heating. Its a less refined grade of paraffin.

Since it can run an engine it contains a yellow dye plus a 2nd invisible marker to detect illegal on-road use. Its not the same grade as road diesel, its thinner, but it can run a diesel engine. The long term effects of this vary widely depending on the engine, some designs are tolerant of it long term, some not.

Supply of 28 second oil is a competitive market that tracks crude oil prices. Its worth phoning around and pitting the suppliers against each other.

Lamp oil

Deodorised dyed paraffin, avoids creating the famous oil heater whiff.

Other oils

Oil thickener

Very thick oils are used on their own in speed reducing devices, eg dashpots to slow the opening of cassette deck doors.

They're also sometimes added to car engines to thicken the engine oil and reduce the blue smoke output of a worn engine.

Oil thickeners are available from car accessory shops.

Penetrating oil

Penetrating oil is a mix of thin oil and an agent such as paraffin which cuts the oil's viscosity.

Penetrating oils are able to penetrate tiny gaps and help unseize corroded fixings. These are much used in car repair.

If no penetrating oil is to hand, a mix of thin oil and a viscosity cutter (eg paraffin) works.

Decorator's oils

Mostly used in decorative finishing

Linseed oil

  • Thins oil based paints, but greatly extends drying time.
  • Enables water based paints to adhere to a greater range of surfaces (mix in 1-2% linseed oil)
  • Makes a range of putties & mastics
  • Thins linseed putty
  • Makes tack rags
  • Used in some finishing oil mixtures for wood

Raw & boiled

Raw linseed oil is simply linseed oil. Boiled linseed oil is now linseed oil plus chemical dryers. Boiled oil sets to a gum over a few days, raw either doesn't set or takes an extremely long time. Boiled should be used in all the above applications except tack rags.

Tung oil

Danish oil

Additives & alternatives

Engine oil & paraffin

A 50/50 mix has several uses.

  • wood preservative
  • penetrating oil
  • corrosion inhibitor - but it becomes slightly sticky

Diesel may be used instead of the paraffin.


Graphite is a solid lubricant. Graphite powder is sometimes added to oils to improve lubrication, and in some cases can even be used instead of oil. Its electrically conductive.

Graphite is used to lubricate locks, as unlike oil it doesn't attract muck.


PTFE aka Teflon is another dry solid lubricant.

PTFE produces toxic products if overheated, and should not be used in tasks where this is a possibility.

PTFE is a good electrical insulator.


Although not often used to reduce friction in DIY, it can be used as a temporary very low friction barrier between materials, such as when moving heavy items into place. Bin bags, rubble bags & dust sheets are suitable supplies.


Can be added to oil to cut its viscosity temporarily. It eventually evaporates.


As paraffin, but even slower evaporation.

Vegetable oil

Several plant derived oils are used for cooking. These lubricate, but over time they gum up badly. This greatly limits their use, but they're fine for jobs such as lubricating screws. Feeding the DIYer is the main use.

Vegetable oil is also occasionally used to clean oily, greasy or bituminous muck off hands. The veg oil is then washed off with soapy water. This sometimes works with clothes too.


Most margerines are plant oil (sometimes fish oil) based, with a large percentage of added water. These can sometimes be used as a last ditch lubricant, but they gum up eventually. The water content gradually dries out, but can cause corrosion.

Hair oils

A little oil added to shampoo makes a conditioning shampoo. Commercial hair conditioners tend to use thick oils such as palm oil, castor oil, jojoba oil etc. The percentage of oil is small enough not to produce any oily feeling or stickiness.

A spoonful of oil added to a litre of shampoo makes a mild conditioner. Oil content can be increased from there for dry hair, but don't overdo it, overconditioning with any conditioner can cause mild stickiness.

Note that the oil separates out on standing (commercial conditioners include an emulsifier to prevent this.) The mix should be shaken before use.

If a 2nd small container is used for the conditioning mix its easy to control how much conditioning you use each time.

Palm oil

Palm oil is a thick semi-solid natural oil, and a widely used hair conditioner in some countries. Its available from Asian grocery stores, and can be added to shampoo to give conditioning properties.

Castor oil

Castor oil is another effective conditioning additive, but availability of the oil is poor, and allergic reaction to the castor bean is a known, albeit rare, phenomenon.

Vegetable oil

Vegetable cooking oils are thinnner than the more usual conditioning oils, and less effective. However milder conditioning works better for some hair types, and less well for some.

Branded products

A few branded products are well known in DIY and deserve their own mention. The well known brands have their uses, but all can be replaced with other good products at a fraction of the cost.

3 in One

3 in One is a brand of oil that attempts to be 3 things in one: lubricating oil, penetrating oil and corrosion prevention. Since these 3 tasks have conflicting requirements its impossible to make a good job of them with one product.

Since its prone to becoming gummy its not recommended as a lubricant. The cans it comes in are handy.


WD stands for 'water displacer.' Water displacers are of limited use in DIY today, primarily used

Machine oil is the temporary coating of choice for preventing rust, and is widely used as a temporary rust prevention coating on imported steel tools.

WD40 also acts as a penetrating oil, though there are cheaper and in some people's opinion better brands out there, such as plusgas.

WD40 is not recommended as a lubricant as it contains mainly solvent, it tends to strip out existing lubricant, and it can become gummy.

WD40 can be used as a cleaner in some situations since it contains Stoddard's solvent. Paraffin is a much cheaper alternative that doesn't leave the sticky residue.

The manufacturer claims 2000 uses for WD40. While many of these are not uses we would rush to recommend, and many are simply duplication, there are some practical ones too. More uses & information.

Appliances have been ruined by the indiscriminate application of WD40. It is not a cure-all and there are common products and materials to which it should not be applied, such as rubber products.


Paraffin gel with additives. Paraffin alone makes quite a good substitute.

Oil kit

Inevitably opinions vary on this, so this list is just intended as a quick starting point guide.

A good kit of oils for DIY may contain:

  • Machine oil (thin lubricant, rust prevention)
  • Engine oil (thick lubricant, car)
  • Paraffin (cleaning, insect repellant, additive)
  • Penetrating oil (frees corroded fixings)
  • Linseed oil (paints, putties, polishes etc)
  • Graphite (lubricating locks)

Not usable

The following might tempt the occasional DIYer, but are not usable for DIY.


Petrol deserves a brief mention simply because is is not usable for any DIY use outside of running engines, but occasionally a DIYer decides to try it as a substitute. Its highly volatile and creates an explosive cloud of gas/air mixture. Inhaling the amount of fumes caused by painting with it can cause anything from migraine to death.

Petrol tankers are marked UN1203.

Glow plug fuel

This is rarely encountered by DIYers, but a few do have it, and its a particularly dangerous potential substitute for oils or solvents. There are various different formulations, several of which contain chemicals likely to be fatal if significant amounts of fumes are inhaled. Its much more dangerous than petrol.



Viscocity is measured in cs (centistokes), seconds, W or WT.

Centistokes are a standardised measure.

Seconds ratings are timings made in various ways, such as how long a given cup with hole takes to empty, or how long a ball takes to fall through the oil.

W and WT are not standardised measures, and the same viscosity oil could receive a different W rating by different manufacturers.


The viscosity of oils varies widely with temperature. Higher temperatures produce a thinner oil. This is of course undesirable for some applications. Multigrade oils (ie 10/30 and 20/50) are designed to vary in viscosity less over temperature change.

Smoky engines

While there is more than one possible cause, vehicles with smoky engines are usually suffering from wear, which allows tiny amounts of engine oil into the cylinder, where it burns, producing smoke with a blue tint. This gets past worn valve seals more often than piston rings.

Replacing 10/30 with 20/50 is often done to reduce smoking. Adding an oil thickener can reduce smoke output further. These are of course not proper cures and not manufacturer recommended, but have got a lot of cars through MOTs.


Oil lines should use only compression fittings.


New oil tanks must now be bunded to prevent contamination in case of leakage.

Storage of large amounts of flammable fuel oils is strictly regulated by law.


Cleanup methods include:


Reusing the oil for something else is sometimes an option. Otherwise oils should be disposed of at the local tip, where its recycled.

Heating boilers have occasionally been modified to burn used engine oil. This is cheap to run, but there are concerns over contaminants, and the relatively viscous oil must be preheated before the boiler can fire.

Its now possible to buy commercial workshop heaters that run on used engine oil.

See Also