Practical Automotive Maintenance: Oil Specifications

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Oil Specifications

07.13

00:00	We're going to begin this course by discussing the different types of oils and their specifications.
00:05	It's a complex subject, but here we'll focus on the essentials.
00:09	Key oil metrics, why we might choose something other than the manufacturer's recommended grade for motorsport, and how to find the correct product for your car.
00:18	Like every subject we cover in this course, we'll be covering how to best perform the oil changing process in a separate practical skills section.
00:26	Oil is one of the most critical fluids in a vehicle.
00:28	Lubricating and cooling parts such as crankshafts, bearing, gears and differentials.
00:34	Broadly, oil falls into three categories.
00:37	Mineral, semi-synthetic and fully synthetic.
00:40	Mineral oil, refined from crude, contains varying molecule sizes and impurities, making it less stable.
00:47	While more prone to breakdown, mineral oil remains useful for older or lower performance engines, and is recommended when breaking in a freshly built motor, as it allows the piston rings to seat properly, while still offering solid protection under load.
01:03	Synthetic oil on the other hand is made from chemically modified or fully synthesized hydrocarbons, making it far more uniform, cleaner and more stable across wider temperatures.
01:15	This means better protection, lower friction and longer service life, though at a higher upfront cost that often balances out through extended service intervals.
01:24	Semi-synthetic, as you've probably already guessed, is a mix between mineral and synthetic oils, created mostly for cost reasons, putting it somewhere in the middle between the two in terms of service life and protection.
01:37	Additives like detergents and anti-foaming agents further protect the engine internals, and it's generally always best to buy oil with the correct additive package, rather than mixing in aftermarket solutions.
01:49	A key additive worth noting is ZDDP, which stands for zinc dialkyl dithiophosphate, a proven anti-wear agent essential for older flat tapper engines and race applications.
02:02	While reduced in modern oils due to emissions concerns, higher ZDDP formulations remain available, though it's worth understanding that they can harm catalytic converters if present.
02:14	Diesel oils typically feature more ZDDP and detergents to handle the higher torque loads and combustion byproducts.
02:22	With the differences between synthetic and mineral oils covered, the other key metric we need to understand is the numbers found on an oil container, which indicate the oil's viscosity.
02:32	Viscosity refers to how easily the oil flows, and the numbers on an oil container indicate its thickness.
02:39	With the higher number, the thicker it is and the less easily it flows.
02:43	Modern multi-grade oils use additives to perform well both in cold start and high temperature running, which is why they've become the standard for today's engines.
02:52	Let's look at a quick example.
02:54	The first number with a W, like the 5 in 5W30, this stands for winter weight, and indicates how the oil behaves in cold conditions.
03:03	The lower this number, the thinner and easier it flows at startup.
03:08	The second number, like the 30 in 5W30, reflects how thick the oil remains at the engine operating temperature, with higher numbers staying thicker under heat.
03:19	All automotive manufacturers publish the oil specification and volume requirements of each vehicle they produce, most commonly found in the user manual that comes with the car or even on a sticker somewhere under the bonnet.
03:31	If not listed there, then it'll also be listed in the vehicle's service manual.
03:36	Failing that, most oil suppliers will also have a dedicated tool on their website that allows us to input the details of our vehicle and receive the correct oil specs in return.
03:46	Some enthusiasts will deliberately deviate from these factory specs.
03:50	For instance, a race engine with looser bearing clearances might switch from a 5W30 to a 10W40 to restore the oil pressure.
03:59	But in a stock engine, using thicker oil than specified can be dangerous as it raises the pressure while reducing the flow.
04:07	While using a thinner oil lowers the pressure, but increases the flow, potentially leaving surfaces unprotected.
04:14	In short, unless we know exactly what we're doing, it's best to stick to the manufacturer's recommendation or the engine builder's advice.
04:22	It's also worth understanding that alcohol fuels like ethanol and methanol complicate lubrication.
04:27	Because these fuels are burnt in greater volumes compared to gasoline, more unburnt fuel can make its way past the piston rings and into the oil, diluting it.
04:37	Being hydroscopic, alcohol fuels also absorb moisture, which can further degrade the effectiveness of the oil.
04:45	This means that much more frequent oil changes are essential in an alcohol fed vehicle.
04:50	These fuels also lack the lubrication qualities of petroleum fuels, strip protective oil films and can degrade additives and reduce viscosity.
04:59	So far, we've discussed the engine oil viscosity, but the same grading and synthetic principles apply to the drivetrain oils.
05:07	Though the viscosity ratings and additives do differ.
05:10	For differentials, transfer cases and manual gearboxes, we often see grades like 75W85, 80W90 or 85W140.
05:22	The logic is the same, higher numbers mean thicker oil at each temperature range, but it is important to always follow the manufacturer's recommendations or a lube guide for the correct spec.
05:33	Drivetrain oils also use specific additives.
05:36	Extreme pressure or EP additives for example, protect gears and bearings under high torque and load.
05:43	API, GL4 and GL5 classifications are associated with gear oils too and reflect different additive levels.
05:51	GL4 is typically recommended for manual transmissions, where GL5 is designed for hypoid gears and axles that generate higher friction and require more protection.
06:01	Fortunately, OEMs and aftermarket suppliers are generally very clear on specifying which to use, so, guesswork isn't often needed.
06:11	We covered a lot of information here, so let's quickly summarise the key points found in this module.
06:16	Mineral oils are less stable, but are useful for older, low performance engines and break in periods on a new build.
06:23	Synthetics offer superior protection and longevity at a higher cost and blends sit in between.
06:29	Additives like detergents and ZDDP further enhance performance, with ZDDP especially important for older engines or higher performance engines.
06:39	Viscosity grades, for example 5W30, show how oil flows at cold start and operating temperature, with multi-grade oils designed to handle both conditions.
06:50	While drivetrain oils use similar grading along with EP additives and API GL classification for gear protection.
06:57	In general, it's best to stick with manufacturer's recommendations unless building a race engine and note that the alcohol fuels demand more frequent oil changes due to the moisture absorption and reduced lubrication.