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Fluids
Checking the oil quality
Can a cheap oil provide all the protection required?
To
a degree, but for the superior performance required for more demanding
applications a better base stock and more sophisticated additive package are
required.
Why is engine oil so much more expensive than other oils?
Mainly because the oil is subject to extreme
conditions in an engine compared to other mechanical systems such as gearboxes,
axles or brakes, and so requires a better base stock and additive package.
These extreme conditions include:
-
High
temperature leading to reduced oil service life as a result of increased
oxidation activity.
-
High
levels of contamination from the atmosphere, fuel/combustion and wear debris
in that order.
-
Many
moving (sliding and rolling) parts resulting in varying forms of lubrication
from boundary lubrication to thick film, in addition to varying metals and
varying load conditions all contributing to a more stressful environment for
the oil.
This is why the oil is not only more expensive, but
generally will not last as long as say a gearbox or hydraulic oils.
The additive package can form up to 30% of the volume of engine oil
compared to just 1-10% of other oils.
There is also the issue that pricing is set based on
the fact that car enthusiasts are sometimes willing to pay a little extra.
The marketing of the engine oil products is very emotional with little
hard science in evidence at times – the old adage that bull baffles brains
applies quite frequently, not helped by incorrect “facts” continually
trotted out across the internet in various forums.
How are oils regulated or compared in the industry?
The
American Petroleum Institute (API) categorises the formulation of oils according
to a standard.
Typical engines of
the period are used as a test bed, and a number of tests are run to ascertain
the performance of oil under test.
If
it meets or exceeds the parameters of the test then it can be classified in that
category.
However, oils in the same
category do not necessarily have equal performance, they may only meet, not
exceed, the requirements of that category.
Current
ratings are based around standard engine design at the time, so modern oils are
designed to withstand higher power outputs, with multi-valve and overhead cam
etc reaching higher rpm than previously.
This
does NOT necessarily mean they are unsuitable for older engines although this is
a general guide in terms of selecting oils.
What are these categories?
For
petrol or Spark Ignition engines, there is a ‘S’ rating, in which stands for
Service.
For diesel or Compression
Ignition engines, there is a ‘C’ rating, in which C stands for Commercial.
Service Oils aka Spark Ignition Oils:
The
ratings started with an API SA rating, and this oil is not recommended for any
vehicle in my opinion except vintage vehicles.
By the 70’s it had moved onto an API SC rating.
During the Nineties it rapidly moved up to as high API SJ, and is
currently at SM.
The oil required
will depend on your driving needs, i.e. daily commuting versus track-day or
motorsport driving.
For the latter,
buy the best you can afford, but for commuting, an API SL or API SJ should be
more than adequate on modern cars unless SM is specified by the manufacturer.
|
Service
Ratings – Gasoline/Petrol/Spark Ignition Engines |
||
|
Category |
Status |
Service |
|
SM |
Current |
For
all automotive engines currently in use.
Introduced in 2004, SM oils are designed to provide improved
oxidation resistance, better wear protection, and better low-temperature
performance over the life of the oil. Some SM oils may also meet the
latest ILSAC specification and/or qualify as Energy Conserving. |
|
SL |
Current |
For
2004 and older automotive engines. |
|
SJ |
Current |
For
2001 and older automotive engines. |
|
SH |
Obsolete |
For
1996 and older engines. |
|
SG |
Obsolete |
For
1993 and older engines. |
|
SF |
Obsolete |
For
1988 and older engines. |
|
SE |
Obsolete |
CAUTION: Not suitable for use in gasoline-powered automotive
engines built after 1979. |
|
SD |
Obsolete |
CAUTION: Not suitable for use in gasoline-powered automotive
engines built after 1971.
Use in more modern engines may cause unsatisfactory performance or
equipment harm. |
|
SC |
Obsolete |
CAUTION: Not suitable for use in gasoline-powered automotive
engines built after 1967.
Use in more modern engines may cause unsatisfactory performance or
equipment harm. |
|
SB |
Obsolete |
CAUTION: Not suitable for use in gasoline-powered automotive
engines built after 1951.
Use in more modern engines may cause unsatisfactory performance or
equipment harm. |
|
SA |
Obsolete |
CAUTION:
Contains no additives. Not suitable for use in gasoline-powered
automotive engines built after 1930.
Use in more modern engines may cause unsatisfactory performance or
equipment harm. |
Commercial Oils aka Compression Ignition Oils:
The API classification is currently at API CJ-4, although this is designed for exhaust gas recirculating (EGR) engines where the soot loading is consequently higher as a result of remixing the unburnt fuel and exhaust emissions into the air intake. Again, the rating has moved on rapidly during the 90’s, and the same comment applies for spark ignition, that is, buy the best you can afford on the basis you want long engine life and enhanced fuel economy. Since diesel engine oils by their nature have a greater degree of detergency and dispersancy than petrol engine oils, these also make suitable oils for older mechanically controlled petrol engines that produce more sludge and combustion products in the sump.
|
Commercial
Ratings – Diesel/Compression Ignition Engines |
||
|
Category |
Status |
Service |
|
CJ-4 |
Current |
Introduced
in 2006. For high-speed, four-stroke engines designed to meet 2007 model
year on-highway exhaust emission standards. CJ-4 oils are compounded for
use in all applications with diesel fuels ranging in Sulphur content up to
500ppm (0.05% by weight). However, use of these oils with greater than
15ppm (0.0015% by weight) Sulphur fuel may impact exhaust after-treatment
system durability where particulate filters and other advanced
after-treatment systems are used. Optimum protection is provided for
control of catalyst poisoning, particulate filter blocking, engine wear,
piston deposits, low- and high-temperature stability, soot handling
properties, oxidative thickening, foaming and viscosity loss due to shear.
API CJ-4 oils exceed the performance criteria of API CI-4 with CI-4 PLUS,
CI-4, CH-4, CG-4 and CF-4 and can effectively lubricate engines calling
for those API Service Categories. When using CJ-4 oil with higher than
15ppm Sulphur fuel, consult the engine manufacturer for service interval. |
|
CI-4 |
Current |
Introduced
in 2002. For high-speed, four-stroke engines designed to meet 2004 exhaust
emission standards implemented in 2002. CI-4 oils are formulated to
sustain engine durability where exhaust gas recirculation (EGR) is used
and are intended for use with diesel fuels ranging in Sulphur content up
to 0.5% weight. Can be used in place of CD, CE, CF-4, CG-4 and CH-4 oils.
Some CI-4 oils may also qualify for the CI-4 PLUS designation. |
|
CH-4 |
Current |
Introduced
in 1998. For high-speed, four-stroke engines designed to meet 1998 exhaust
emission standards. CH-4 oils are specifically compounded for use with
diesel fuels ranging in Sulphur content up to 0.5% weight.
Can be used in place of CD, CE, CF-4 and CG-4 oils. |
|
CG-4 |
Current |
Introduced
in 1995. For severe duty, high-speed, four-stroke engines using fuel with
less than 0.5% weight Sulphur. CG-4 oils are required for engines meeting
1994 emission standards. Can be used in place of CD and CE oils. |
|
CF-4 |
Current |
Introduced
in 1990. For high-speed, four-stroke, naturally aspirated and turbocharged
engines. Can be used in place of CD and CE oils. |
|
CF-2 |
Current |
Introduced
in 1994. For severe duty, two-stroke-cycle engines. Can be used in place
of CD-II oils. |
|
CF |
Current |
Introduced
in 1994. For off-road, indirect-injected and other diesel engines
including those using fuel with over 0.5% weight Sulphur. Can be used in
place of CD oils. |
|
CE |
Obsolete |
Introduced
in 1985. For high-speed, four-stroke, naturally aspirated and turbocharged
engines.
Can be used in place
of CD oils. |
|
CD-II |
Obsolete |
Introduced
in 1985. For two-stroke cycle engines. |
|
CD |
Obsolete |
Introduced
in 1955. For certain naturally aspirated and turbocharged engines. |
|
CC |
Obsolete |
CAUTION: Not suitable for use in diesel-powered automotive engines
built after 1990. |
|
CB |
Obsolete |
CAUTION: Not suitable for use in diesel-powered automotive engines
built after 1961. |
|
CA |
Obsolete |
CAUTION: Not suitable for use in diesel-powered automotive engines
built after 1959. |
API ratings
for Gear Oils
Gear oils are also classified by the American Petroleum Institute under the GL rating system.
See Viscosity Explained for an understanding of the SAE Gear Oil grading system.
Again, gear oils can be either mineral or synthetic and because they are not as challenged as an engine oil, they last longer. IN fact some car manufacturers now do a fill-for-life with quality synthetic. Multi-grade gear oils are also more common now, as there is some period of warm up and possible extra drag when cold. Synthetic based multi-grade oils are less likely to sheardown than the mineral based multi-grades with VI Improver additives.
MGBs and a number of other British classics use a Laycock overdrive. The oil specified for this is usually engine oil in 20W50 format and gear oil is not recommended. However, earlier non-overdrive gearboxes were specified with EP90 oil. Some owners complain of sluggish overdrive operation when the gearbox is cold so it is possible that the box has been incorrectly filled with EP90. The EP90 is not so much a problem with the copper in the gearbox but more to do with the friction drive through the cone clutch and subsequent slipping.
API classification subdivides all transmission oils into 6 classes (sourced from Wikipedia):
| API GL-1 |
oils for light conditions. They consist of base oils generally without friction modifier additives. GL-1 may contain small amounts of anti-oxidant additives, corrosion inhibitors, depressants and anti-foam additives. API GL-1 oils are designed for spiral-bevel, worm gears and manual transmissions without synchromesh rings typically found in agricultural applications. |
| API GL-2 |
oils for moderate conditions. GL-2 contain anti wear (AW) additives and are designed for worm gears. Recommended for proper lubrication of agricultural machine transmissions. |
| API GL-3 |
oils for moderate conditions. GL-3 contain up to 2.7% anti-wear additives. Designed for lubricating bevel and other gears of truck transmissions. GL-3 are not recommended for hypoid gears. |
| API GL-4 |
oils for various conditions - light to heavy. GL-4 contain up to 4.0% effective anti-scuffing additives. Designed for bevel and hypoid gears which have small displacement of their axes, truck gearboxes, and axle units. GL-4 are recommended for non-synchro gearboxes of US trucks, tractors and buses and for main and other gears of all vehicles. GL-4 oils are basic for synchronized gearboxes, especially in Europe. |
| API GL-5 |
oils for severe conditions. They contain up to 6.5% effective anti-scuffing additives. The general application of GL-5 in this class are for hypoid gears having significant displacement of axes. GL-5 are recommended as universal oils to all other units of mechanical transmission (except gearboxes). GL-5 oils, which have special approval of vehicle manufacturers, can be used in synchro manual gearboxes only. API GL-5 oils can be used in limited slip differentials if they correspond to the requirements of specification MIL-L-2105D or ZF TE-ML-05. In this case the designation of class will be another, for example API GL-5+ or API GL-5 LS. |
| API GL-6 |
oils for very heavy conditions (high speeds of sliding and significant shock loadings). They contain up to 10% high performance anti-scuffing additives. They are designed for hypoid gears with significant displacement of axes. Class API GL-6 is not applied any more as it is considered that class API GL-5 is enough to meet the most severe requirements. |
| API MT-1 |
oils formulated for thermal stability, with 10% EP additives and friction modifiers. Generally suited for non-synchromesh manual gearboxes in heavy duty service such as bus and truck fleets. |
ATF or Automatic Transmission Fluid is purposely coloured with a red dye to aid condition checking. If the oil darkens it indicates a need for change and possible problems in the unit. Some owners use it in their MGBs and Midgets as the colour can aid identification of the source of the persistent oil leak and it won't cause harm to the overdrive, which is, in effect, a form of automatic transmission utilising hydraulic power to switch in and out.
However, ATF usually conforms to various OEM specifications such as Dexron and Mercon. Check with the handbook for your vehicle as to which is required.
Owners of MGs fitted with the LT77/R380 box have seen a number of oils types specified by the factory. During the 1990s Texaco provided a specification for most Rover gearboxes, MTF94. A copy of the spec sheet is here.
Where can I find the API rating?
The
API rating is usually shown in a doughnut or circle on the side of the oil
container, or may be listed in the small print.
Not all manufacturers show this on their containers, possibly for the
reason that not many people know what it means, or more cynically, because it
hasn’t been fully tested.
In
independent testing that I have been involved with in the past, there have been
significant differences in wear control between major brands.
Don’t write off smaller brands, either.
Some smaller brands specialise in a type of oil and do not carry the
overheads of a major supplier.
They
dedicate their facilities to a type of base stock, operate in a cleaner manner,
and use higher quality base stocks with specifically formulated additive
packages.
But better quality and
performance will usually cost more.
For
older engine designs, if you want to avoid the very latest API spec, use one
that is designed for older engines.
Halfords,
Castrol, Comma and Millers do a range of classic oils in the UK, and Penrite is
also available from Australia. Millers even do a specific 20W50 for the A
Series with the gearbox in the sump.
The advice with classic petrol engines is to look for modern oils that have been formulated for diesel engine use as well. If the oil has a CH-4 or CI-4 rating then this should be more than adequate for valve train protection, even if it is an SL rated oil. An SM oil will still offer protection but in a different way to the way SL/CI-4 oils did using ZDDP.
Now, it is true to say that newer engines should not run on oils formulated for older engines, but they can, albeit with reduced engine life and performance. There's a tendency in the classic car community to think older engines can't run on newer oils, not helped by the marketing of specialist oils for the classic community. Older engines can run on newer oils. If you look at the way API define each new category they state "For xxxx (year) and older engines", so consequently even up to SM oils should be acceptable for older engines. That said, SM qualifying oils have been formulated for the very latest energy conservation which puts emission control above wear control. But that said, oils that qualified for an earlier category may automatically qualify for the next new category simply because, as said, an oil must meet or exceed the minimum criteria.
There has been a recent trend by some experts to suggest not using an API oil higher than SG. The reasoning given is these lack sufficient Zinc protection. As mentioned earlier, Zinc levels are still much higher than they ever were in the SA/SB/SC oils on which the A and B Series would have first run. Certainly, in 1993, in the UK, exhaust catalytic converters became compulsory fitment for vehicle manufacturers, and Zinc is damaging for these. Now API SG is for engines built in 1993 and older. But API is a North American focussed organisation so I am not sure if there is any link between the change in test parametres for SG to SH categories and the UK requirement for catalytic converters which were being used on many cars long before 1993, anyway. The API ratings do state for 199x engines and older and do not specifically exclude engines built before 1979. By rights MGBs should be on SB/SC oils given the date of its original engine, however, experienced engine builders seem to differ in their views regarding synthetics and modern SL spec oils with some praising these oils and some hating these oils.
In fact, as SG is an obsolete category now you would struggle to find an SG oil today, without going to the specialist classic car oils, and these probably won't have been submitted for API SG testing.
This
is what the
British Lubricants
Federation (BLF) has to say regarding advice given to owners of petrol
engines:
"Any
oil which does not carry an API or ACEA performance specification or some type
of approval from a major vehicle manufacturer is highly suspect and must be
assumed to fall into the lowest category, i.e. API SA, which became obsolete in
the 1930s when the first additive engine oils (API SB) began to appear!
It
is essential that oils of at least the correct requirement are used, although
higher specification oils, in the same category, should be used as soon as they
become available if maximum benefits in fuel economy, engine protection
performance and operating costs are to be obtained.
However,
it must be appreciated that an engine which has been operating on a very
poor-quality lubricant for some time may well be beyond saving, since it is
likely to have suffered build-up of sludge deposits which could be displaced by
the detergency power of a modern good-quality oil. Blocked oilways could well
result.
Likewise for diesel engine owners.
"Any oil which does
not carry an API or ACEA performance specification or some type of approval from
a major vehicle manufacturer is highly suspect and in the interest of safety
must be assumed to fall into the lowest category, i.e. API CA, which became
obsolete in the 1950s.
It is essential that oils
of at least the correct requirement are used, although higher specification
oils, in the same category, should be used as soon as they become available if
maximum benefits in fuel economy, engine protection performance and operating
costs are to be obtained. However, it must be appreciated that an engine which
has been operating on a very poor-quality lubricant for some time may well be
beyond saving, since it is likely to have suffered build-up of sludge deposits
which could be displaced by the detergency power of a modern good-quality oil.
Blocked oilways could well result.
Other Ratings – ACEA
Figure 6 - ACEA Ratings Explained
A/B : gasoline and diesel engine
oils
-
A1/B1 Stable, stay-in-grade oil intended for use at extended drain intervals in gasoline engines and car & light van diesel engines specifically designed to be capable of using low friction low viscosity oils with a high temperature / high shear rate viscosity of 2.6 mPa*s for xW/20 and 2.9 to 3.5 mPa.s for all other viscosity grades. These oils are unsuitable for use in some engines. Consult owner manual or handbook if in doubt.
-
A3/B3 Stable, stay-in-grade oil intended for use in high performance gasoline engines and car & light van diesel engines and/or for extended drain intervals where specified by the engine manufacturer, and/or for year-round use of low viscosity oils, and/or for severe operating conditions as defined by the engine manufacturer.
-
A3/B4 Stable, stay-in-grade oil intended for use in high performance gasoline and direct injection diesel engines, but also suitable for applications described under A3/B3.
-
A5/B5 Stable, stay-in-grade oil intended for use at extended drain intervals in high performance gasoline engines and car & light van diesel engines designed to be capable of using low friction low viscosity oils with a High temperature / High shear rate (HTHS) viscosity of 2.9 to 3.5 mPa.s. These oils are unsuitable for use in some engines. Consult owner manual or handbook if in doubt.
C : Catalyst compatibility oils
-
C1 Stable, stay-in-grade oil intended for use as catalyst compatible oil in vehicles with DPF and TWC in high performance car and light van diesel and gasoline engines requiring low friction, low viscosity, low SAPS oils with minimum HTHS viscosity of 2.9 mPa.s. These oils will increase the DPF and TWC life and maintain the vehicles fuel economy. Warning: these oils have the lowest SAPS limits and are unsuitable for use in some engines. Consult owner manual or handbook if in doubt.
-
C2 Stable, stay-in-grade oil intended for use as catalyst compatible oil in vehicles with DPF and TWC in high performance car and light van diesel and gasoline engines designed to be capable of using low friction, low viscosity oils with a minimum HTHS viscosity of 2.9mPa.s. These oils will increase the DPF and TWC life and maintain the vehicles fuel economy.
-
C3 Stable, stay-in-grade oil intended for use as catalyst compatible oil in vehicles with DPF and TWC in high performance car and light van diesel and gasoline engines, with a minimum HTHS viscosity of 3.5mPa.s. These oils will increase the DPF and TWC life. Warning: these oils are unsuitable for use in some engines. Consult owner manual or handbook if in doubt.
-
C4 Stable, stay-in-grade oil intended for use as catalyst compatible oil in vehicles with DPF and TWC in high performance car and light van diesel and gasoline engines requiring low SAPS oil with a minimum HTHS viscosity of 3.5mPa.s. These oils will increase the DPF and TWC life. Warning: these oils are unsuitable for use in some engines. Consult owner manual or handbook if in doubt.
-
SAPS : Sulphated Ash, Phosphorus, Sulphur
-
DPF : Diesel Particulate Filter
-
TWC : Three way catalyst
-
HTHS : High temperature / High shear rate viscosity
E : Heavy Duty Diesel engine oils
ILSAC
The International Lubricant Standardization and
Approval Committee (ILSAC) also has standards for motor oil. Their latest
standard, GF-4 was approved in 2004. A key test is the Sequence IIIG, which
involves running a 3.8 L, GM 3.8 L V-6 at 125 horsepower (93 kW), 3600 rpm,
and 150 °C (300 °F) oil temperature for 100 hours. These are much more severe
conditions than any API-specified oil was designed for: cars which typically
push their oil temperature consistently above 100°C (212°F) are most
turbo-charged engines, along with most engines of European or Japanese origin,
particularly small capacity, high power output.
The IIIG test is about 50% more difficult than
the previous IIIF test, used in GF-3 and API SL oils. Engine oils bearing the
API starburst symbol since 2005 are ILSAC GF-4 compliant.
JASO
The Japanese Automotive Standards Organization (JASO)
has come up with their own set of performance and quality standards for petrol
engines of Japanese origin.
For 4-stroke gasoline engines, the JASO T904 standard
is used, and is particularly relevant to motorcycle engines. The JASO T904-MA
and MA2 standards are designed to distinguish oils that are approved for wet
clutch use, and the JASO T904-MB standard is not suitable for wet clutch
use.
For 2-stroke gasoline engines, the JASO M345 (FA, FB,
FC) standard is used, and this refers particularly to low ash, lubricity,
detergency, low smoke and exhaust blocking.
These standards, especially JASO-MA and JASO-FC, are
designed to address oil-requirement issues not addressed by the API service
categories.
API, ACEA