(Q) What is the difference between road and racing oils?
(Q) Does oil have to be warm to do its job properly? Is it important to warm up your engine before driving at speed?
(Q) What are the most important substances added to the refined base oils? & What do they do?
Top Ten Frequently Asked Gear Oil Questions –
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(A). The difference between Road and Racing oils
The days of incense-like ‘R’ oils for racing only are past, except for classics. At least as far as 4-strokes are concerned, the best synthetic types are ideal for both race and road use. (Well, that’s our policy. All of our race oils are on the retail price list!) With ultra-precise components, high-pressure pumps and high engine RPM there has been a move to special synthetic low cavitation/low drag oils to release more power with no reliability loss. These can be (and are!) used in road cars and bikes, but if 0W/20 is not mentioned in the user handbooks, there will always be some warranty risk.
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(A). How is an oil manufactured; transformed from the black sludge that comes out of the ground, into the nectar-like substance we pour into our engines?
Crude oil, which is usually very thin, (contrary to popular belief!) is distilled into light and heavy fractions, with several intermediate ones. (The evil left-overs are used to fuel the 15 million cc/40RPM diesels in the giant oil tankers that bring the crude to the refinery.) The lighter fractions, usually more than 90% of the original crude, are converted into petrol and diesel. Some of the heavier oils, (still dark and smelly!) go through several processes to clean them up and remove wax. Out of about a dozen oily products 4 clear, bright amber oils are commonly used to blend modern engine and gear oils. These are roughly equivalent to SAE 10, 20, and 30 engine rating and 140 gear rating. Oil refineries also produce all sorts of gases and chemical compounds which can be used to build up 'tailor-made' lubricants: synthetics!
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(A). Does oil have to be warm to do its job properly? Is it important to warm up your engine before driving at speed?
Yes, it does have to be at least warm, and preferably hot. Most people find metal at 60ºC too hot to touch, yet 60ºC is too cold for oil in an engine that’s going flat-out. The best approach is to use a good 10W/40 or even a 5W/40, and take it easy for the first couple of miles, especially in very cold weather.
For racing, a really good warm-up is essential, except perhaps with special 0W/20 low-drag race oils. The trouble is, oil pumps are very good at pushing oil out at 60PSI, but unfortunately there is only 14PSI (atmospheric pressure) pushing it in! (Even less at high altitude.) So it’s easy for an oil pump to pull voids or pockets of vacuum in the oil if it doesn’t flow fast enough into the oil pickup. This ‘cavitation’ obviously reduces the amount of oil the pump can deliver.
Also, in high-speed bearings the oil can be too thick to keep up with the high rubbing speeds reached in modern engines so the ‘wedge’ or hydrodynamic’ effect breaks down. I know it goes against common sense (whatever that is) but the faster a bearing is turning the thinner the oil should be. (A 4cm. diameter main bearing is rubbing its shells at 56 MPH at 12,000RPM! So to avoid cavitation the oil needs to be 10cSt or less, which is SAE 30 if the oil happens to be at 100ºC, or SAE 40 if it’s at 110ºC.)
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(A). What are the most important substances added to the refined base oils? & What do they do?
In the Dark Ages engines used blends of refined mineral oils 'straight', with nothing added. The trouble was, even in the slow-revving engines of 80 years ago the oil didn't last very long, and the engines didn't either. Black sludge and corrosion were the killers, and both were tackled in the 1950s with detergent and antioxidant chemicals. (When I was a lad, I used to visit a mate of me Dad's who rebuilt the very popular side-valve Ford engines. The thick crap inside these things was unbelievable! The valve tappets were moving in holes in solid blocks of carbon!) The detergents washed the carbon from fuel combustion off the bores and out of the ring grooves, and at the same time reduced bore and piston ring corrosion. The antioxidants stopped the oil reacting with oxygen in the air, which cut acid sludge formation which in turn reduced corrosion and oil way blockages. Some antioxidants had the useful side-effect of reducing wear as well. This added up to longer oil and engine life, both improving about three times. (Straight oil had to be changed every 1000miles, and even lightly-stressed engines running on it were ready for a full overhaul at 15-20,000.) OK, I admit there were design and metallurgical improvements, but they needed that vital 'liquid component' to be fully effective. Later came dispersant compounds which held the carbon as tiny particles in the oil which didn't settle out anywhere, and slipped through the oil filter as if it wasn't there.(Solid bits in well-used modern oil are about 1/1000mm across; the pores in an oil filter are at least 15 times bigger.)
The other big problem with oil used to be cold starting. It was usual to have SAE 20 Winter or 'W' grades, and SAE 30 or 40 Summer grades, and even the so-called Winter types would defeat the starter in serious cold weather. Unfortunately, oil is very thick when it's cold, and very thin when it's hot. To have an oil thick enough to look after a hard working engine, you had to use a grade which was too thick when it was cold. The answer was (and is) multigrade! What was needed was an oil that behaved like a 20 'W' grade in the cold, but only thinned down to a SAE 40 or 50 when really hot; yes, 20W/50! This can be done by mixing thin oil with thick polymers based on plastics and synthetic rubbers; these don't do much in the cold, but as the oil warms up they unwind and thicken it up to some extent. The oil still thins down, but not as quickly as a polymer-free or monograde type. Multigrades started to catch on around 1960, but these pioneer types were easily ruined by mechanical shear effects, more so in gearboxes than engines. These days the better quality polymers resist shear even in combined engine/transmissions, so it is essential to use good quality shear-resistant types in a motorcycle, which gives its oil a hard time in both engine and gearbox.
Incidentally, there are large amounts of these additives and polymers in there, it's not just 'a little bit of this, a little bit of that'! A good quality mineral 10W/40 can be 80% base 20% additive chemistry, and guess which is the expensive ingredient!
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- What does API GL mean?
API stands for American Petroleum Industry and GL stands for Gear Lubricant, see below for their definitions:
API GL-1 Straight mineral oil
API GL-2 Mild EP for worm gears
API GL-3 Mild EP for spur and spiral bevel gears in axles and transmissions
API GL-4 Medium EP, MIL-L-2105 quality, moderate severity hypoid gears, manual transmissions
API GL-5 High EP, MIL-L-2105D quality, all hypoid axles, some manual transmissions
API GL-6 Extra high EP, now obsolete
- Is it important to select the right API GL rating?
Yes. Selecting the correct gear oil performance level will provide the best protection to the components of the transmission.
- What do the SAE grades mean?
SAE stands for the Society of Automotive Engineers. The SAE classification system is a way of defining how thin or how thick an oil is. This is known as an oil’s viscosity. The classifications are listed here in order of increasing thickness: SAE 75W, SAE 80W, SAE 85W, SAE 90, SAE 140, SAE 250.
- What does EP mean?
EP means extreme pressure and refers to the additive used in gear oils. This additive is designed to stop metal-to-metal contact taking place between transmission components. The EP additives are usually based on sulphur and phosphorous. These elements bond to the metal surfaces where there are points of extreme pressure and temperature, forming a sacrificial chemical layer. The sulphur gives gear oils their characteristic smell.
- Will synthetic gear oils and mineral gear oils mix together?
Yes, but beware that there two kinds of synthetic gear available: polyalphaolefin (PAO) based and polyalkylene glycol (PAG) based. PAOs are basically a man made version of mineral oils (although with greatly improved properties) and can therefore be mixed with mineral oils. In fact, semi-synthetic products have mineral and synthetic base fluids in them, so obviously, they must be able to mix. PAGs, on the other hand, will not mix with PAOs or mineral oil. Utmost care must be taken when using this kind of product.