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What are BASE OILS?

All oils are made up of base oils and additives. Not all base oils are created equally however. The API classifies these into 5 main groups.

Group III and IV base oils are 100% synthetic. Some very high quality Group II oils (called Group II Plus) are also accepted as having synthetic like performance. When looking at the table below, think of saturates (relates to aromatics and other hydrocarbon molecules) and sulfur levels as the degree of purity of the oil. The Group III products used by Penrite are over 99% pure. PAOs are even more pure than Group III oils. Group I and II base oils are considered mineral.

Synthetic base oils are used for two main reasons; greater oxidation stability (for longer oil life) and low volatility ( to decrease oil consumption ). In order to meet the ACEA specifications on oil volatility, many lighter engine oil viscosity grades must use a percentage of these products, especially if Group I base oils are used.

Group V contains all other base oil types not included in Groups I, II, III and IV eg Esters, Naphthenics, etc. From a Penrite perspective, we choose the combination of the above base oils to ensure maximum performance for a given oil.
































Hydro-Processed (Hydrocracked) Base Oils – What do they look like? 

Group II: Hydro-Processed

  • 400°C

  • 500psiH

  • Removes sulfur and nitrogen

  • Converts aromatic hydrocarbons to cycloparaffins

Group III: Severly Hydro-Processed

  • 425-430°C 

  • 1,500-3,000 psi H

  • Converts cycloparaffins to paraffin chains

What is the difference between mineral, semi-synthetic and full synthetic base oils?

Full Synthetic oils can be engineered for many different applications. They can be derived from naturally occurring resources such as crude oil that has been serverely hydrocracked to where the carbon chain has been altered. They are defined by the API as Group III base oils. One of the benefits of synthetics is the quality and purity of the base oil. They contain less impurities than mineral based oils such lower sulfur and wax levels, as well as less hydrocarbons. Synthetic base oils give outstanding performance especially as lower viscosity oils. They naturally have a higher viscosity index which stops them from becoming too thick when cold and too thin when at operating temperature. Hence these oils flow more easily on start up providing engine protection when it is most needed. They are much less volatile than mineral base oils meaning they are more stable at temperature, burn less and require less additives that can be the cause of engine deposits. They are also less prone to oxidation providing better anti corrosion protection for the engine. The latest specification Full Synthetic Engine oils can offer up to three times more protection, five times better cleansing and less than half as much engine wear compared with oils 20 years ago.

Premium Full Synthetic are Full Synthetic engine oils derived from Laboratory made base oils such as PAO (Group IV) and Ester (Group V)

Semi Synthetic oils are a blend of synthetic and mineral base oils. To be classified as semi synthetic at Penrite, they need to be at least 20% or more Full Synthetic oil. Other names such as "Synthetic Fortified" or "Synthetic Blend" are also names used for these oils. The levels of Full Synthetic base oil will vary considerably between different brands and specifications. Semi Synthetic engine oils provide the good points of both mineral (cost) and synthetic (performance) oils and can be engineered to offer excellent protection, obliging performance, generally at a lower cost than Full Synthetic oils.

Mineral or conventional engine oils are derived from naturally occurring deposits such as crude oil and are refined by different methods to produce base oils. There are many levels of mineral base oils from low to outstanding quality. They are graded by the API as either Group I or Group II, the latter undergoing intense refinement (Hydrocracked) with the use defined by the application. Generally, the more the product is refined, the more pure the base stock. The more pure the base stock, the better the performance as an engine oil. Good quality mineral base oils can offer nearly all the same specifications as the more expensive synthetic types especially if mixed with high performance additive packs. They are extremely popular in the manufacture of older specification, higher viscosity engine oils but can also be used to manufacture low viscosity, fuel efficient and latest specification engine oils.

Synthetic Base Oils

PAOs – Poly Alpha Olefins (Group IV):
PAOs are derived from the oligomerization, usually of 1-decene. Oligomerization refers to a process where a monomer or a molecule is linked to many others of the same type to form a long chain.

1-decene is further derived from the oligomerization of high purity ethylene (C2H4).

PAOs are extremely pure:
• Identical molecules. • No sulfur or phosphorus. • No wax.

Benefits of PAOs:
• Excellent cold flow properties.
• Highly resistant to thermal breakdown.
• Excellent shear stability.

ESTERS (Group V):
Manufactured by reacting an acid and an alcohol to
give ester plus water. There are many types of esters,
such as diesters and polyolesters.

Benefits of Esters:
• Resistant to thermal breakdown.
• Good metal-wetting ability.
• High film strength.
• Good shear stability.

100% PAO & ESTER Full Synthetic


Blended using premium full synthetic 100% PAO (Poly Alpha Olefin) Group IV & Ester Group V base oils for maximum heat resistance and high performance.

100% PAO's (Poly Alpha Olefin) are extremely pure due to their complex petro-chemical manufacturing process. As a result, the chemical oil structure formation is “flat” compared to lower grade full synthetic chain structures.

Having a “flat” oil structure creates less friction between chemical structures which allows the oil to effectively become ”more slippery.”

The combination of 100% PAO's & ESTER together with our premium additives, provides the ultimate protection against oxidation due to their outstanding heat resistance.

Other product benefits include oil pressure stability, longer engine life and greater engine performance.

Esters in Base Oils


It is believed that the first synthesized hydrocarbons were created by Friedel & Crafts in 1877. It was in 19 that the commercial development of synthesized hydrocarbons was created by Standard Oil of Indiana. At that time there was not a lot of interest in these types of compounds. From 1938 to 1944, thousands of esters were evaluated in Germany with excellent results. Their first uses though were in military aviation in the 1940's. It was the space age that helped create a greater appreciation for the benefits of synthetic lubricants. Jet engines raised the bar on what was required of a lubricant. The high speed, high heat and cold temperature performance requirements of modern jets created a demand for a new kind of lubricant. 
Following WWII, the first use of diesters by the British in turboprop engines for high temperature performance were used and from the early 1970's various synthetic fluids were developed to meet the demands of new and more efficient high performance engines and machines in the automotive industry. The first 100% synthetic diester based engine oil to pass the API sequence tests and receive API qualification was in 1972.

What is an Esther?

In simple terms, esters can be defined as the reaction products of acids and alcohols. They are manufactured to produce predetermined molecular structures designed specifically for high performance lubrication. These synthetic base stocks are primarily branched hydrocarbons which are thermally stable, have high and low viscosity indices and are extremely pure. For automotive purposes, esters can be the base stock (base oil) for a lubricant or be used in conjunction with other base stocks such as PAOs, Group III, Group II's etc. to make full synthetic or semi synthetic lubricants.

Ester Characteristics 


Esters have a polarity that attracts them to one another as well as to positively charged surfaces. When the molecules are attracted to one another it requires more energy to vaporise them giving them a higher flash point and lower evaporation rate.


The polarity also allows them to be attracted to metal surfaces to create a strong film of lubricant, improving lubricant and lowering energy consumption and friction heat.

Detergency / Dispersancy

Esters can disperse oil degradation by-products that might otherwise be deposited as sludge, allowing for cleaner operation of the engine. They can also improve the additive solubility in the final lubricant.


While esters are stable against oxidative and thermal breakdown, the ester linkage provides a vulnerable site for microbes to begin their work of biodegrading the ester molecule. This translates into very high biodegradability rates for ester lubricants and allows more environmentally friendly products to be lubricants. This is important, especially for developing two stroke oils that provide great lubricant and have the ability to be biodegradable at the same time.


As with any product, there are some downsides to esters. One concern when formulating with ester base stocks is compatibility with the elastomer material used in the seals. All esters will tend to swell and soften most elastomer seals however, the degree to which they do so can be controlled through selection. Another disadvantage with esters is that they can react with water or hydrolyse under certain conditions.

What are Esters used in?

There are many different kinds of esters commercially produced for a broad range of applications. They have been used for automotive lubrication now for approximately 45 years. They are also used in synthetic refrigeration lubricants used with CFC replacement refrigerants. Within the realm of synthetic lubrication, a relatively small but substantial family of esters have been found to be very useful in severe environment applications.

Ester Based Automotive Engine Oils

In automotive applications, esters in many cases have given way to PAOs and Group 3 synthetics due to cost and their formulating similarities to mineral oil. Nevertheless, esters are often used in combination with PAOs or Group 3 based synthetic oils in order to balance the effect on seals, solubilize additives, reduce volatility, and improve energy efficiency through higher lubricity. The more ester used will obviously affect the price of the lubricant as it is very expensive as a base stock compared with PAO or a Group 3 Synthetic.

There are very little, if any, 100% full ester based 4 stroke engine oils in the automotive aftermarket. The best way to check is by obtaining a Safety Data sheet for the product or contacting the manufacturer of the product.

Penrite Engine Oils with Ester

Penrite manufacture a range of engine oils that utilise PAOs and esters in their formulations.

Penrite 10 Tenths  Racing Range

Penrite 10 Tenths Premium Synthetic Range

Penrite Motorcycle PAO & Ester Synthetics Range

Penrite Biomarine Full Synthetic 2 Stroke Oil

What are the benefits of using Synthetic oils?

The benefits of using lubricants made with synthetic base oil are numerous. Synthetic Base oils have better low and high temperature viscosity performance, especially at higher to extreme operating temperatures. Synthetics also have better cold flow properties that offers better start up protection and oil flow when cold that benefits modern engine technology.

Synthetic Base Oils have better resistance to oxidation and thermal breakdown than mineral based oils that can reduce the formation of deposits and oil sludge. The better resistance to heat, oxidation and increased shear resistance also means they are harder to burn and can be used to extend drain intervals in certain applications.

Synthetic Base Oils have a more consistent and uniform molecular structure than mineral based oils so they tend to create less friction which can benefit fuel economy.


In summary, Synthetic Base Oils offer -

  • Improved stability at high operating temperatures

  • Increased Shear Resistance

  • Less chance of thermal breakdown

  • improved fuel economy

  • Harder to burn or evaporate

  • Extended service opportunities depending on application

  • Oxidation resistance

  • Better oil sludge prevention

  • Fast start-up protection

  • Better lubricant and less friction

  • Longer component life

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