It sounds plausible, and is often a topic for discussion without a clear outcome.
Do we need a detailed technical appraisal? I doubt anyone will stake their reputation or personal liability on assuring an outcome based on a longer service interval then the manufacturer recommends.
There is a lack of definitive alternate evidence to support behaving differently. There is variation between different models, in how they are used, in driver style and quality variation within a single model variant.
Are consumers being taken advantage of as suggested by the original topic article concerning Subaru commended service intervals? Yes IMHO.
This is about much more than just engine lubrication?
A discussion on what is the best choice of engine oil vs service for a motor vehicle is worthy of it’s own topic and discussion.
P.S. or down the rabbit hole, if anyone is wondering.
Please excuse the generalisation. The following is intended only to outline some of the issues or scope around a discussion on motor oils.
There are endless discussions on motoring focused forums about engine oil types and selection. Many only encourage confusion and inconsistency. Some serve very particular interest groups. The industry is awash with marketing hype and a multitude of competing products. And manufacturers are all progressively updating engine designs.
As a simple head spin read the attached link. It is pure marketing wrapped around some basic technical detail.
For Australia which has very limited requirements to deliver low emissions, and also fuel costs well below Europe, there is more latitude in what we are able to import as product.
Engine technology in use today varies between light alloy construction, high tech multipoint fuel injection, variable valve timing, computer control (ECU), to designs still rattling away with a single point fuel injection system, and cast iron! And that is without considering turbos!
Places like the USA, Southern Italy and Spain all see similar summer conditions or worse, than most of coastal Australia where 90% of our vehicles are driven. Even Tokyo is known for humid 30-35C wet summers?
Cars in Europe and Japan probably do much stop start and short distance driving. No different to downtown Sydney or Melbourne really?
Simple comparison might be enough to reason that for a typical motor vehicle in urban Australia the servicing needs should be no different than most other big motoring nations. Notably given Aust is a little slacker about pollution controls and emission performance we might even be able to relax how often some servicing needs are met.
If there are international exceptions they might reasonably relate to driving in sub zero conditions or the Simpson desert daily.
For technical simplicity the manufacturers recommended grade (EG 5W-30) and minimum specification of engine oil is important. What ever the grade recommended it will typically suit an Aussie vehicle for the whole of the year. We also typically do not have genuine endless extremes of cold (eg Canada winter) or heat (Central Australia summer) in Sydney, Melb etc.
The car makers oil specification (eg expresses by a code such as SF, SN, etc) is a minimum standard. Higher specification oils may last longer in service. Synthetic oils are highly refined and modified (chemically manipulated) made from the same feed stock as everyday mineral oils. As a consequence the synthetic modified products are more stable and have less variation in the chemistry, they handle higher temperatures (nothing to do with the outside environmental temperature) in the engine better and have the ability remain usable for a longer service life. That is assuming the engine oil blender has not skimped on the additives package. Many quality base oils remain usable in service past life of their additives.
Most engine wear is attributed to limited lubrication when an engine is first started. Having the recommended grade of engine oil for the service environment plus the quality of the additive package is critical to minimising this wear. All other attributes or properties of oils used for ICE engine lubrication there after quickly descend into the mire of expert disagreement and amateur ignorance. Cold sub zero winters are more of a challenge for engine lubrication on starting than Australia’s milder climate.
Once up and running 99.99% of engine lubrication relies on the viscosity of the lubricating fluid. And modern engines quickly achieve a stable running temperature. The same operating temperature whether the engine is in a Darwin summer or Canberra winter.
More modern engines with tighter clearances reduce oil loss (burning) which reduces emissions and also enables lighter grades (less viscose) engine oil to be used. This reduces engine friction caused by viscose drag between the moving parts of the engine which improves fuel economy.
Owners of high performance and older vehicles may have differing and some special needs.
Irrespective of the views of the more sceptical that service intervals are set based on profit margins at dealerships and spare parts sales.
Servicing to schedule is considered by many to be a good insurance policy against the unexpected breakdown. This seems to be self evident. Although the lack of hard evidence of an epidemic of broken down vehicles is not proof. There is also a large element of guilt driven marketing with the need to service often. Erring on the conservative or safer ground might also be wisdom, but is it necessary?
With more knowledge of each individual vehicle, usage patterns, and analysis of a sample of engine oil at each service, it would be possible to do better, and possibly run longer. Assessing each vehicle individually removes some of the uncertainties. The cost of the sample and analysis? About the same as the cost of the next basic service.
Cars now have enough smarts to track actual usage, performance cycles and condition. It could enable the trip computer to make an informed estimate of when the next service should be provided, rather than fixed time or distances alone?
However at least for the warranty period the intervals suggested are ultra conservative. It appears to serve several vested interests, including those of the owner.
For a better understanding and in-depth discussion Monash University and others offer post graduate studies in Engineering Maintenance (Terotechnology) and Tribology.