A guide to Gulf Western diesel oil

What a diesel oil has to do

A diesel engine runs higher compression and produces more soot and acidic by-products than a petrol engine, so its oil needs stronger detergents and dispersants to hold that soot in suspension and neutralise the acids. Gulf Western diesel oils are blended for that: wear protection from a lubricating film between moving parts, thermal stability so the oil does not break down under high temperatures, and cleanliness, keeping sludge and deposits from forming so the engine stays efficient over time.

Mineral or synthetic

The range comes in two main families. Mineral oils are refined from crude oil, are the traditional choice and are often more economical; they suit older engines and simpler lubrication needs. Synthetic oils are engineered for higher performance, with better protection at extreme temperatures and under heavy loads, and longer life between changes. Modern common-rail diesels and anything that tows or works hard are usually better served by a synthetic.

Reading the viscosity grade

Gulf Western diesel oil is available in grades such as 15W-40, 5W-30 and 10W-30. The first number (with the W, for winter) describes how the oil flows when cold; the second describes its thickness at operating temperature. A 15W-40, for example, is a common all-round grade for older and heavy-duty diesels in Australian conditions, while a 5W-30 suits many modern light-duty diesels that call for a lower viscosity. The grade on its own is not enough: the oil also has to carry the API, ACEA or manufacturer specification your engine requires, and a diesel with a particulate filter needs a low-SAPS oil.

Choosing the right one

Three things decide it:

• The manufacturer's specification: the owner's manual lists the grade and the specification the engine needs; start there
• Driving conditions: extreme heat or cold, heavy loads, towing, stop-start traffic and dusty tracks all push the oil harder, and favour a synthetic with better wear protection and thermal stability
• Advice: the RedPoint team can match the Gulf Western range to your vehicle and how you use it

Change intervals and the signs of tired oil

A typical diesel oil change falls every 5,000 to 10,000 km depending on the vehicle and the manufacturer's guidance; heavy towing or harsh conditions put you at the shorter end. Watch for the signs the oil is past its best: dark, sludgy oil on the dipstick, a level that has dropped noticeably, unusual engine noise or more exhaust smoke than usual. Change the filter with the oil every time.

Storage, mixing, warranty and disposal

The questions that come up most:

• Storage: keep the oil sealed in a cool, dry place out of direct sunlight so moisture cannot get in, and check the date on older stock before using it
• Mixing oils: not recommended. Each oil is formulated as a package, and mixing can reduce performance. If you must top up with something else, make sure it meets the same specification
• Warranty: manufacturers require oil that meets their specification to keep the warranty valid. The right Gulf Western grade keeps you compliant; the wrong grade can void it
• Disposal: never pour used oil down a drain or onto the ground. Take it to a council drop-off point or a service station or workshop that accepts used oil

Get advice from RedPoint

If you are considering Gulf Western diesel oil for your vehicle or machinery, the RedPoint team can help you pick the right product for the engine and the work it does. Alongside the oils we carry the filters that go with them, so a service can be sorted in one visit or one order.