Fuel Additives & Engine Oil

Keep machinery and vehicles running and in tip-top condition with engine oils from Cromwell online. We stock a wide selection of engine oils and fuel additives to suit all of your needs from leading brands, like Makita®, Molyslip® and our own brand Solent®.

What is engine oil?

As the gears in a gearbox move against one another, the friction and heat they generate will, over time, degrade and deform these components. Engine oil or gear oil provides much-needed lubrication to reduce friction and damage.

Why buy engine oil?

To ensure the required performance and smooth movement of gears and other internal components, engine oil or gear oil is a must-have.

When are engine oils used?

Engine oils are often thought to be exclusively used in cars when they're designed for use in any machine that uses gears. While cars are the primary users of engine oil, this product is also required for some industrial machines. This type of oil must be machine specific however, as typical gear oil complete with additives will damage machine components.

Engine oil types

Engine oils start off life as very similar liquids, however, the way they're sourced and processed creates the different 'types' we're used to.

Fully synthetic engine oil   -   While still sourced from oil wells, synthetic oil is processed and refined in laboratory conditions to produce a high-performance engine oil that lubricates and protects components at low temperatures. It's often paired with PD (Plastic Deformation) additives to ensure excellent lubrication over a wide range of temperatures and pressures.

Mineral engine oil   -   Named as such due to the way it's extracted (like mineral deposits are extracted), mineral oil will contain EP additives of phosphorous and sulphur, which provides high-performance load carrying benefits and product stability at high temperatures.

Two-stroke engine oil   -   Also called 2T, this type of engine oil is designed for use with handheld tools such as strimmers, chainsaws and scooters and is completely different to the oils already discussed in this list. It's intended to be mixed with petrol in the sump and cannot be substituted with other types of oil.

Considerations when choosing engine oil

Viscosity - the viscosity of engine oil determines the density of lubrication covering the gears and other internal components. Thicker oil will create a thicker film which will improve performance and prevent wear.

Additives - grade means quality and this is often coded using letters which can be found on the oil packaging. Graded using the letters A, B, C and E, A is reserved for petrol engines, while B, C and E covers diesel in progressive engine size and power requirements.

Eco-credentials - the continuous mining of fossil fuels has a detrimental effect on the environment, which is why Double Separation Technology (DST) will likely play a big part in recycling and reusing engine oil to reduce the human impact on the planet.

Engine oil jargon buster

Engine oils are graded according to GL numbers, which is an abbreviation of Gear Lubricant. There are four grades which start with the most basic, GL-1 to the highest performing, GL-5.

Let's break it down...

• GL-1 - This grade of oil generally has a low viscosity and low additive content. It's mainly used for older gears but can be bought in thicker variants to combat poor oil seals.

• GL-3 - This has a low concentration of additives and is a small step up from GL-1. Mainly used for French and Italian patented cars.

• GL-4 - This grade has a high extreme pressure (EP) performance and is often specified as the type of oil to use.

• GL-5 - The highest performer on this list, this grade of oil is specified for use on Hypoid gears, which appear in cars from 1960s production onwards.


Is higher or lower viscosity gear oil best?

As a rule of thumb, higher viscosity oils (thicker) are ideal for lower speed, higher load gears. It provides a thick coating of lubricant and provides high-level protection against corrosion and deformation. The opposite is true of lower viscosity (thinner) oils, which perform well in high-speed, lower-loaded gear systems, where a thinner film provides better cooling performance at high speeds.