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Welcome to the Aston Workshop news section. This section will update regularly, enabling you to keep up to date of changes and new information relating to the Aston Workshop and the Aston Martin Marque.
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Q: Can modern fully synthetic engine oil be used in a classic era Aston Martin and if so what are the benefits?
A: We have reached the time in the year when many owners are reawakening their cars in anticipation of the summer motoring months ahead. One of the questions many ask when servicing their car ahead of this time is should they specify the use of fully synthetic oils, and do the benefits justify the additional cost?
The first point is that a traditional mineral based multigrade oil, examples of which include Duckams 20/50W and Millers classic oil (also 20/50W) and their Castrol oil equivalents remain fully fit for the purpose.
Provided they are changed twice per year or after 3000 miles (5000kms), these oils will continue to provide good results as they were the type of oil that the engine was designed to be used with.
Use of relatively low detergent oil such as these is also important when an engine has already had considerable service. This is because a more modern high detergent oil will wash away the carbon deposits around piston rings and bearing journals with a consequent increase in oil consumption and lowering of oil pressure.
Semi-synthetic oils have a wide acceptance in the general car service market. They have a higher oil stability (though not as good as that with a fully synthetic oil), improved lubricity and a higher viscosity stability over time. As such, their service life is usually and typically 6000 miles or an annual change (10000Kms) in many car service schedules, whereas the service life of an original mineral based oil is typically 6 months or 3000 miles.
There will be a worthwhile increase in oil life for the classic car motorist who uses their car on a regular basis and whose annual mileage is typically 4000 or 5000 miles each year. However, in line with many oils of their type, semi-synthetic oils have a higher level of detergent and so their use would not be recommended in engines which have already seen extensive service with the older type of mineral oil.
Fully synthetic oils have the advantage, apart form improved lubricity and minor benefits in fuel consumption and also have a much higher viscosity stability. A service life of at least 10000 miles (15,000 kms) or annual change is normal. There are also benefits at engine start-up and with it a reduction in the rate of general wear, particularly with a cold engine. However, many of these are of marginal benefit to many classic car motorists and it would be difficult to justify the additional cost over a more traditional mineral based oil. As a cost comparison, a mineral oil will typically cost around £12 per 4 litres, a semi synthetic £25 and a fully synthetic £35. Synthetic oils also have a higher detergent level than mineral oils and hence could not be recommended for high service life engines.
So, is there any advantage to use of synthetics in our type of car. Well the answer is as always, it depends. One of the key advantages of fully synthetic oil is a much greater range of viscosity values. So for a person who typically likes to motor fast down the auto routes and who operates their car in high ambient temperatures, there can be a significant benefit in higher and more stable oil pressure and a worthwhile reduction in oil consumption. If nothing else, a stable oil pressure and reduced oil consumption makes for improved peace of mind if nothing else. Typical equivalent viscosity ratings are 10/60W and 5/50W. Synthetic oils also confer major benefits to those who highly stress their engines on track days or sprints.
To sum up, for the average classic car motorist clocking up around 2500 miles per year, there is little benefit to paying extra for semi or fully synthetic oils. Higher mileage motorists using their car on the road obtain some benefit from increases service life which will in general compensate for the additional cost. Full Synthetics only become of any benefit when travelling fast over long continuous distances in high ambient temperatures or where the engine is highly stressed during track day use and sprinting.
Finally a few do's and don'ts
- In general stick to the use of oil viscosities recommended when the car was new
- Always use a reputable brand of oil and do not be tempted to economise. Remember, a change of oil is a lot cheaper than an engine rebuild.
- Always change the oil filter when changing the oil.
- It is normal for the oil to blacken in use but a more rapid discolouration than normal, or where there is evidence of fuel contamination or high water content, err on the safe side and bring the oil change forward and investigate the causes.
- Never keep oil in an engine beyond its normal service life
- Never allow the oil level in the engine to drop below a safe level; in short check the oil level frequently and ideally before any car journey.
- Always monitor oil pressure and if there is an unexplained drop. stop the engine and investigate.
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