Can I mixed synthetic oil with mineral oil?
In most cases mineral oils can be mixed with semi-synthetic or full synthetic oils. Gulf Western’s range of mineral, semi-synthetic and full synthetic engine oils can be mixed. In some cases, synthetic esters and PAG grades cannot be mixed with other grades. If you are unsure, please give Gulf Western technical a call.

What does API and ACEA stand for?
API – American Petroleum Institute & ACEA – Association des Constructeurs Europeans d’Automobiles (the European Automobile Manufacturers Association)

What does Zinc do in an engine oil?
Over the years there has been a lot of misinformation about zinc. Zinc, or zinc dialkyldithiophosphate is a compound that was introduced over 70 years ago as an anti wear additive to engine oils. In recent years, there has been considerable pressure to reduce zinc levels in engine oils. In part because they are (in higher concentration) not compatible with diesel particulate filters and catalytic converters, and in part because of concerns of long term human toxicity. Modern oil formulations are trending towards much lower levels of zinc and other anti-wear additives and friction modifiers have been introduced.  

What does it mean when my diesel engine oil goes black?
The black colour in oil is from soot (unburnt carbon) produced when diesel is burnt in an engine. The oil should go black as it disperses and suspends the soot. If not held in a finely dispersed form by the oil, the soot particles would stick together forming sludge that could block oil-ways. This is overcome by the dispersant additives in the oil. Additionally detergent additives prevent soot from building up on metal surfaces (like a non-stick coating on a fry pan).

One of the major concerns in modern engines is wear to bearings, cam lobes, followers and rockers from the abrasive effects of soot particles joining together. Hence engine manufacturers specify limits for soot in used oil and that the oil still has enough detergency to stop the soot sticking to metal components.

Essentially the oil is doing its job. If an oil takes time to go black it is not performing as well as an oil that goes black quickly.

Modern low emission engines produce more soot than their predecessors. This is particularly so if fitted with Exhaust Gas Recirculation (EGR). It is the job of the oil to hold that soot in a finely dispersed form. An API CJ-4 oil such as Top Dog Global Plus or Top Dog Global Mineral, can safely hold 4% soot. In a 50 litre sump this is 2kg of soot! No wonder it will go black. This shows how good the oil is and how well it protects your engine.