All internal combustion engines burn some oil. Some may burn more than others but they all consume oil. There is no average limit on the volume an engine should consume over a service period. Some engines will comfortably see out a service period and still show little consumption whilst other engines may have needed to have been topped up several times or more. Consumption is also not set by age either. A new engine may consume oil whereas a very high kilometre engine may consume very little.

Manufacturers build their engines to consume some oil. A good example of this is demonstrated by the latest industry specifications. One of the biggest improvements over the previous oil grades is the LSPI protection. Low speed pre-ignition can partly be caused by oil in the combustion chamber pre-igniting under pressure. How did the oil get there in a new motor? For vehicle manufacturers all over the world, their single biggest goal is to reduce emissons. To reduce emissions, you need to reduce economy. So an engine that has extremely tight tolerances, may use more fuel than one with not so tight tolerances. So if the latter uses a little bit of oil in between services, then that does not go against it's fuel economy rating and is not really measurable as an emission as it is normally so low. 

So why do engines consume oil and why do some consume more than others? Firstly, apart from a seal or gasket failure, the common theory that very low starting weight viscosity oils such as 0W-XX and 5W-XX burn when they start up is not normally correct. When an engine is cold, it will be at its tightest before heat expands the metals in the block and head. So in theory, this is probably the time when an engine is least likely to consume oil as the engine's tolerances are at their tightest point.

On the other side of the multigrade viscosity table, many will argue that the oils are too thin at operating temperature. They proclaim 0W-20 oils and 5W-30 oils are too thin. Interestingly, the second number in a multigrade viscosity is  the same thickness as a mono grade number. So a 5W-30 should be as thick as a SAE 30 at operating temperature. a 5W-20 the same as a SAE 20 engine oil. Multigrades were introduced in the 1960's and prior to that many vehicles ran on a Mono Grade oil such as SAE 30 or even SAE 20. So really, oil thickness at operating temperature has not really changed in 50 years. Engines will run a bit hotter in modern cars but this is normally not the cause of consumption.

So why do some engines burn more oil than others?
Higher oil consumption could have a number of causes. Some of the most common can be:

1) Using oil with a viscosity that is too low for the application

2) Viscosity breakdown

3) Using a low quality oil

4) Damaged or worn compression or oil rings

5) Damaged or worn valve stems and seals

6) Oil dilution

7) Gasket and seal leaks

To slow oil consumption, a higher viscosity grade oil can be used, especially an oil with a higher operating temperature viscosity. Oil burns when at its hottest and therefore thinnest viscosity. By using an oil with a higher operating temperature viscosity, it will hold better film strength when at operating temperature making it less prone to being worked past worn engine rings or valve stems, seals and guides. As an example - If your vehicle uses and burns a 10W-30 engine oil, you may consider changing the oil to a 10W-40 or 10W-50 grade oil. This will give the engine the same starting viscosity with a higher operating temperature viscosity which should slow down oil consumption. If you are using a 5W-30 grade oil and you move to a 10W-30 grade oil, you are not likely to quell the consumption only increase fuel consumption.

Always make sure that when choosing to use a heavier oil, it meets the performance specifications required by the manufacturer. Some vehicles may not be able to use a heavier oil because the performance specification required can not be met by heavier oils. In these cases, regular topping up may be the best course of action. The same with vehicles that are under warranty but make sure you have the correct specification and an approved product if required by the manufacturer. 

Using a low quality lubricant can also lead to excess consumption. Lower quality oils can shear quickly and hence suffer viscosity loss, especially at operating temperature. What might start out as a 10W-40, might end up being a 10W-20, which may not be suitable for some engines. The loss of viscosity also reduces film thickness and therefore increases frictional heat. The frictional heat will cause wear and the temperature increase will cause an increase in oxidation in the oil. The rates of oxidation approximately double with every 10‑degree rise in temperature. Oxidisation can lead to carboxylic acids attacking metals and causing corrosion. If this process is not controlled, the lubricant decomposition will lead to oil thickening, sludge formation, and the formation of varnish, resin, and corrosive acids.

Another cause of consumption can be oil dilution. If using fuels such as E85, expect to use approximately 33% more fuel than unleaded petrol. If this fuel is not all burnt as part of the combustion process, then it could end up in the sump. The same with some diesel engines, the oil can actually look like it is increasing on the dipstick. Obviously dilution will affect the oils performance and make it easier to burn. Diluted oil can also lead to increases in engine wear and premature parts failure.

Overall, modern vehicles are very reliable. They normally start first go, don't break down often and don't require much in between services. This is what we expect from modern vehicles, including being able to make it from one service period to the next without requiring an oil top up. In some vehicles though, this is unavoidable.

I’m sure we have all heard it at some stage, when someone has changed their engine oil and they tell you that the used oil came out “as clean as a whistle”, “like is was new oil”, or words to that extent. Truth be known, if you have completed a service period and the oil comes out with no discolouration, clean and translucent like it went into the engine, then you probably need to change the type or brand of oil you are using.

Modern engine oils are highly detergent to keep engine internals clean and free from build ups of combustion by-products such as  -

• Carbon Dioxide
• Carbon Monoxide
• Sulphur Dioxide
• Nitrogen Oxides
• Lead
• Particulate Matter

Detergents used in engine oil are oil soluble bases that are derived from the organic soaps or salts of calcium, magnesium, sodium or barium. They are polar in nature, which allows them to cling to the surfaces of particles. They serve two principal functions -

1. They lift any deposits from the surfaces of the engine to which they adhere to and then chemically combine to form a barrier film, which keeps the deposits from coming out of suspension and coagulating.
2. Detergents neutralize any acids formed by the combustion of the fuel by chemically reacting with the acids in order to form harmless neutralized chemicals.

The number of particles that can be contained by the detergents is limited. When the number of particles exceed the capacity of the type of detergent chemistry being used, deposits can form. Therefore, it is necessary that the engine oil be drained before this happens if engine cleanliness is to be maintained.

Another additive used in engine oil is “Dispersant”. Dispersants help to prevent sludge, varnish and other deposits from forming on critical surfaces. They

• Suspend particulate contaminants in the oil
• Minimize & prevent sludge formation
• Suspend oil‑insoluble resinous oxidation products
• Prevent particulate‑related abrasive wear
• Prevent viscosity increase
• Stop oxidation‑related deposit formation.

Dispersants are used in petrol and both light and heavy duty diesel engine oils. Dispersant's are polar additives that are used to disperse sludge and soot particles for the purpose of preventing agglomeration, settling and deposits. Dispersant's form a micelle enveloping particles and keep them finely divided.

 These “Micelles” can trap deposit precursors up to 0.05 microns in size by providing a thick absorbed barrier film or they can also hold larger particles up to 0.1 micron in size by electrical charge repulsion. In this state, the acids and deposits cannot see the engine's metallic surfaces.

A good way to highlight how dispersants work is to watch dirty clothes washing in a top loading washing machine. The detergents in the washing powder/liquid release the dirt and then it is suspended in the water by the dispersants, so when the machine drains the washing water, the dirt and grime are washed away in the rinse. If this process did not happen, the clothes would come out of the machine dirty, not clean.

A modern engine oil is a combination of base oil and additive pack. The additive pack can be anywhere from 8% to 25% of the volume of the product. Approximately 80% of the additive pack is detergent and dispersant. This shows that modern specification oils have a high performance emphasis of cleanliness inside the engine. API SN grade oils have 40% better sludge prevention and 30% better piston cleanliness than the previous grade (SM) engine oils. With this emphasis on cleanliness, an engine oil meeting the latest international specifications should not be coming out of an engine clean after a service period.

No engine is 100% efficient at combustion. All engines, no matter how modern, produce by-products of combustion. Some of these by-products get circulated back through the engine via exhaust gas recirculation (EGR) and come into contact with the engine oil in the crankcase of the motor. Therefore, the oil needs to prevent these contaminants from attaching themselves to the engine internals preventing corrosion and sludge build up inside the engine. Sludge occurs when the engines oil can no longer carry or effectively remove particle matter inside the engine, or when the oils detergents and dispersants are saturated.

So apart from lubrication, heat dissipation and acid neutralising, engine oil is also expected to clean, prevent and suspend contaminants and particle matter until it is flushed at an oil change. So of course, oil should come out of the engine a much darker colour than when it went in. In diesel engines, discolouration happens very quickly and is generally darker than that of a petrol engined vehicle due to soot produced by combustion. An engine running on LPG will burn fuel more completely but they still produce unwanted acids that are corrosive to internal engine parts. The used oil though, will appear a lighter colour than petrol or diesel following a service interval.

So next time someone tells you that their oil came out of the engine following a service period and it was clean and new, you will know that the oil they used, was not doing the job it was meant to do. Consequently, if it comes out dark and dirty, you will at least know it has done part of the job that is was supposed to do inside the engine.

LSPI is a premature combustion event, that happens prior to spark ignition in turbocharged and smaller petrol engines. It happens when engines operate at low speeds and high loads. It can lead to extremely high cylinder-pressures and can induce a heavy knock. These can be audible knocking noises and continued exposure to these conditions can cause an engine failure, including broken spark plugs and cracked pistons. LSPI cannot be predicted and corrected by adjusting spark timing. As such, mitigating pre-ignition involves altering the design of the engine or lubricant to help avoid this emerging issue.

Causes of LSPI

There are several theories to explain LSPI.

• Oil entering the combustion chamber mixes with fuel and auto-ignites.
• Deposits create an ignition source for LSPI.

Evidence shows that both could be responsible, and they are not necessarily mutually exclusive

What role does Engine Oil have with LSPI

The most noticeable impact has been from the detergent chemistry. Oils with higher concentrations of calcium, that is used in many detergent systems, have been shown to increase the frequency of LSPI. The exact chemistry of the detergent is less important to LSPI than the calcium content. Conversely, magnesium-based detergents do not seem to promote LSPI. In addition, there are other additives that can also help reduce LSPI events. This provides an opportunity to formulate oils to prevent LSPI, whilst maintaining the level of detergency needed to help keep engines clean and neutralise acids generated during the combustion cycle as well as meeting extended service intervals.

There are other additive and base oil components that can reduce LSPI. Molybdenum compounds have been shown to decrease LSPI when used at high levels. Base oils can also affect LSPI. Both the quality of the base stock (i.e. Group II versus Group III) and the viscosity can have secondary effects on LSPI. The effect on LSPI from these other lubricant aspects are not as significant as the detergent system but can shift the LSPI frequency in oils that are more prone to LSPI.

Providing additive solutions to help mitigate LSPI

New and upcoming engine oil specifications will include LSPI prevention. ILSAC GF-6 is expected to include a Ford engine test based on LSPI event prevention (reduction). Thus, all oils that make GF-6 claims will need to be formulated to address LSPI. GM's dexos1™ Gen 2 specification addresses the issues LSPI and is recommended for all modern GM petrol engines.

Petrol engine oils can be used in diesel engines if the oil meets the minimum requirements specified by the manufacturer for that particular engine. For example, if the manufacturer specifies API CF or later specification as being suitable for the engine, then as long as the engine oil meets API CF or higher specifications (ie CF-2, CF-4, CG-4, CG-4, CH-4, CI-4, CI-4 Plus) then there is no issue. Obviously the later the specification, the better it will be for the engine.

No it isn't, and conversely, there is nothing stopping you moving from Mineral to Semi Synthetic or Full Synthetic engine oils. An engine may run or feel a little different and take a little while to settle down if oil type is changed as not all oils are made from the same base oil and additive types, hence they do not all perform the same (which can be the case going from brand-to-brand or grade-to-grade), but after that, there shouldn't be any problems. It is more important to find the "Right oil for the right Application" than the base oil type ensuring the oil meets the specifications required by the manufacturer. Some manufacturers may actually specifically recommend the use of synthetic oil and there are some applications, such as Mazda rotary engines, where the manufacturer will specify only using a mineral oil.

If your vehicle is powered by LPG (Liquid Petroleum Gas) or is dual fuel (Petrol/LPG), running on LPG can bring a significant cost saving over running a vehicle on petrol, but ensuring you utilise the correct oil is imperative.

There are not many vehicles that were released with OEM fitted LPG systems. This being, the case, most LPG vehicles have been converted and therefore it is important that the correct oil specification and viscosity is used. As a starting point, use the Penrite Product Selector to find the original vehicle. Note down the Specifications and Viscosities of the recommended oils and see if they match one of the Penrite HPR GAS oils.

If the specifications and viscosity are not compatible with HPR Gas 10 or HPR Gas 20W-60, then the recommended oil should be used as per the Product Selector. Special attention should be paid to the service interval as to not exceed the normal servicing period.

Many vehicle types have several specifications and viscosities of engine oil they use. To find out if your vehicle can use a dedicated LPG oil from our range or you need further assistance, contact our Technical Help Line on 1300 736 748 or our on line chat or forum service.

Sometimes a dye is added for product identification (e.g. DEXRON-III and DEXRON-VI will always be red as it is part of GM's requirements). Base oils and additives have natural variations in colours (i.e. browns to pale golds) due to different types of base oils and additive packs used to make the finished product, but this has no bearing on the performance of the oil. Used oil is usually darker than fresh oil due to various causes (e.g. soot, age, oxidation, contamination, etc.). This is normal and it shows that the oil is doing part of its job correctly in holding the contaminants in suspension until the next oil change.

The performance properties of lubricants will remain intact for many years provided they are in protected storage and not exposed to severe high/low temperature cycles and outside contamination. Generally, the simpler the oil formulation, the longer the oil will remain satisfactory. As a rule, shelf life of lubricants is around 5 years, if stored correctly.

A vehicle Owners Manual can tell you many things about your vehicle including what lubricants to use and how much is required. Understanding what some of the classifications and symbols are can be confusing for some consumers.

In the example following, the owners manual is advising that the minimum requirement for this vehicle in terms of specification is API Service Classification - SM with Energy Conserving. It is also suggesting that the engine oil be a minimum ILSAC GF-4 fuel economy grade. The markings shown on the image are those used for licensed API service classifications which can appear on product labelling.

The owners manual is also stating that the viscosity grade required can be either - 5W-30, 5W-40, 10W-30, 10W-40 or 10W-50 depending on the climate in which the vehicle operates. It also advises that 5W-30 is the preferred viscosity for this vehicle.

The owners manual may also have more information and alternative grades based upon the vehicles appplication and climatic environment

For the same vehicle as above, the manufacturer also specifies some alternative viscosities for very high temperatures and for heavy duty applications

The manufacturer in this case also advises that Synthetic engine oil is fine for the vehicle as long as it meets with the same requirments and servicing intervals as conventional oil.

Other manufacturers my use alternative Specifications as in the following example where the manufacturer speciies an ACEA grade with their own specification requirement.

The owners manual will also advise on other lubricants such as Manual Transmission oil, Automatic Transmission Oil, Differentials and coolants

Above is a recommended viscisity guide for Gear Oils. The owners manual stipulates that the API Oil Classification that must be used is API GL-5

The owners manual may also contain quantities needed for servicing which is generally found in the maintenance section  of the owners manaual