I have been doing some research on engine oils for the Aero 8, so I thought I would put together a guide that might be of use for others.What does it all mean?Viscosity
One of the main differing factors we look at when choosing the correct oil for our car is the viscosity, an example of this would be "0w30". This denotes the viscosity of oil at hot and cold temperatures, hence the two numbers.
The first number followed by the letter W 0w
30 is the viscosity of that oil at low temperatures (W stands for winter), the lower the number the thinner the oil.
A thinner oil at lower temperatures is beneficial because it flows more easily and therefore can better protect the engine when it is first started from cold. If the oil is thick when cold, it will not circulate as freely causing increased engine wear and reduced fuel economy.
The second number 0w30
is the viscosity of that oil at normal operating temperatures. The higher the second number, the thicker the oil.
If the oil is too thin when hot, it may not protect as effectively. If it's too thick you may lose some efficiency.
Based on the above it would seem that the best oil would have the lowest first number, and the highest second number. However there are many factors dependant on engine design, tolerances to heat, cleanliness and other running parameters, emissions, performance and climate that dictate what oil will best work with a specified engine type. Specifications
The main specifications you will see on the back of most engine oils are ACEA, API and OEM specifications.ACEA
(Association des Constructeurs Europeens d'Automobiles) governs oil specifications for European cars, for an oil to meet a designated ACEA specification it must pass a sequence of tests under ACEA. The ACEA specifications are designated as:
A = Petrol engines
B = Diesel engines
C = Engines needing oils that are catalyst compatible
E = Heavy duty diesel enginesAPI
(American Petroleum Institute) designates an oils quality standard with two letters, for instance SB.
The first letter is either:
S = Service (Petrol)
C = Commercial (Diesel)
The second letter will be another alphabetical letter, the further along the better the oil quality. So a B is better than an A, and so on.OEM
specifications will differ per manufacturer, for instance BMW will include a Longlife specification, such as BMW Longlife-04 or (LL-04). This will mean the oil has been tested and approved to meet certain requirements which BMW require to meet longlife servicing, such as a low ash content for diesel engines.Type of oil (quality)
Last but not least we have the types of oil you can purchase:Mineral
= Lowest quality made from crude oil.Semi-synthetic
= Mixture of synthetic oil (synthetics undergo are far more rigorous refining process) and mineral oil.Fully-synthetic
= Fully synthetic oil with no mineral oil.Ester-Synthetic
= The most advanced fully synthetic oil with superior friction and performance properties.
Most modern engines will require a semi-synthetic oil as a minimum requirement, each of these oil types will comes in various specifications and viscosity‚Äôs as explained above.
It is also worth noting that not every viscosity, type and specification variable is available. This is because oil manufacturers tend to make oils for the majority of modern applications not all, for instance a vintage engine may well have very specialist oil requirements that none of the above cater for. It might need something very thick and technically inferior because of the high tolerances that it was designed to run with. Equally some engines are not designed to run on a certain viscosity grade ‚Äď however certain oils such as Esters are only produced in that grade, because they are designed for maximum performance applications and as such manufacturers do not cater for the whole market within their business models. This also explains variances between available oils, for instance Mobil 1 might produce different grades for their Fully-synthetic range than Castrol do, and so on.What do I use for an Aero?
BMW state the following requirements for the M62 V8 derivatives:Viscosity
0w30, 5w30, 0w40, 5w40Specification
BMW Longlife-04 (ll-04)Type of oil
Now this leaves an awful lot of choice, so I will try to cover the different options, but as a brief summary as long as an oil meets one of the above viscosity‚Äôs, both specifications and is a minimum of a semi-synthetic quality it will meet the minimum requirements for the engine for road use, however if you wish to do track days, maximise the protection of the engine, maximise economy and performance you should exceed those specifications.
I consulted Opie oils who have recommended for maximum performance/protection using an Ester fully synthetic 5w40
, this is for a number of reasons:
- Higher ‚Äėnormal operating temperature‚Äô viscosity provides better protection under hard use / essential if the car is used on track.
- Ester oils cling to metal surfaces, so the interior of your engine is coated with oil at all times meaning instant cold start protection. This is especially valuable with the BMW VANOS system, which has been known to have wear related failures.
- Ester oils reduce friction further than normal oils, leading to improved protection. This often means engines run smoother and quieter as well.
- Esters make the oil more stable, making ester based oils ideal for hard use.
- 0w30 oils tend to burn off quicker in BMW petrol engines than other viscosity grades.
Now you may be thinking why not use a 0w40 oil, as that will provide even more cold start protection in freezing temperatures ‚Äď well in theory yes, but few Ester fully synthetic oils are manufactured in that grade, meaning very little choice is available amongst the top manufacturers.
No need to worry though, a 5w oil is rated at -35C to flow the same as a 0w oil will at -40C. For our climate a 5w oil won't be troubled.
If you are still with me you might then notice that most of the Ester based oils do not list the manufacturers, ACEA or API specifications. This does not however mean they do not meet the specs and cannot be used, it is in fact because they are designed primarily for maximum performance and are often used in race applications, as such they do not bother with the hassle of getting these specs approved as it is not their main focus. They do however generally exceed all of these specs.
This is where the advice of an expert (in this case Opie oils) was valuable, they work with the oils day in and out and have a deep understanding of all the specs and requirements, as such they can decipher what can and can‚Äôt be ignored. I shall let Tim from Opie explain this below with regards to the BMW V8:
Specs are a good place to start, if you use an oil that meets the standard spec listed for an engine, then it will be okay, but it does mean the oil will be standard. When upgrading the oil, you tend to get away from the manufacturer specifications and sometimes it can be relatively simple or it can require a bit of knowledge about what each spec means.
The M62 is from the mid 90s and being realistic, oils were generally pretty straightforward then, there were no considerations for low emissions or long life servicing. BMW then brought out the LL98 spec in 1998 and that meant that the service interval was about 15000 miles, although there was still no consideration for emissions. In 2001, LL01 appeared and that stretched the service interval to 20000 miles/2 years, but again no emissions restrictions as there were no diesel particulate filters to worry about. In 2004 LL04 appeared and that stuck with the 2 year/20k service interval, but used a low ash formula so as not to upset the DPFs that BMW had started fitting to the diesels. Since then LL12 and LL14 have been introduced, but they are not things I'd consider for your engine, and most BMWs still use the LL04 spec.
As your engine is originally pre LL specs, doesn't have a sensitive emissions system and as far as I am aware, is supposed to be serviced annually or at 10000 miles, then there is no need to use a LL spec oil. Looking at my data, it lists a LL01 5w-40 as the standard choice for it, but as your engine is pretty straightforward with its requirements, there is no need for LL01 or LL04.
So in summary:Standard use
ACEA C3, BMW ll-04 spec
0w30, 5w30, 0w40, 5w40
An example being BMW Twin Power Turbo SAE 0w30Increased protection
Upgrade to Fully-synthetic oil
ACEA C3, BMW ll-04 spec (however this is less relevant with higher quality oil)
0w30, 5w30, 0w40, 5w40
Recommended: Motul 8100 X-Cess, Millers XF Longlife, Castrol Edge/Magnatec, Fuchs GT1 XTL/Supersyn, Shell Helix and Mobil Super 3000Track use/maximum protection
Spec even less relevant now as any of these oils is of very high quality
0w40, 5w40 spec. The higher second number ‚Äú40‚ÄĚ denotes better protection at higher temperatures, essential for track use.
Recommended: Fuchs/Silkolene Pro S, Millers CFS/CFS NT+, Motul Sport/300V, Red Line and Gulf Competition
Fuchs Pro S seems to be one of the favourites.
I hope this is useful to everyone, I must also say a quick thanks to Tim of Opie oils, who gave up a lot of time to explain and pass on his knowledge with relation to oils suitable for the BMW V8.