When Should You Switch to a More Viscous Oil?

Engine oil


Following the insight he gave us into what types of oil to put in a recently purchased vehicle, our associate, Dr. Stevan Dimitrijevic, digs deeper in order to help you land on whether to switch to a more viscous type of oil if the mileage on your vehicle’s clock shows more than 200.000 km or if your vehicle is pushing 10 or more. We highly recommend that you read the following.

If the engine is in good condition, there are a few answers to this question.

1. If the instruction states SAE 5W-30 (or 5W-40) i 10W-40 (or higher) as well, then it gets easy:

a) You can stick to a lower level of viscosity, which, coming from the standpoint of the quality of lubrication, is the best solution. This comes recommended if you tend to use your vehicle intensively (covering more than 15.000 km per year), especially in heavy, high-exploitation conditions (e.g. taxi service, trailer towing, field driving, covering lots of short distances accompanied by lots of cold starts etc.).

more viscous oil


b) You can switch to a more viscous oil (10W-40) for the purpose of lowering the cost of vehicle maintenance. This comes highly recommended when using your vehicle in normal-exploitation conditions and when covering a relatively small number of km per year (less than 15.000 km).

2. If the instruction doesn’t state 10W-40 or higher:

a) It’s best to stick to the original recommendations. It’s the simplest and best method.

b) The vehicle is already old, which is why high-quality semi-synthetic types of oil, such as Total Quartz 7000 or Elf Evolution 700 (in several forms), can provide protection to the engine, along with suitable care, thus prolonging its duration. The engine composition gaps get bigger as the engine gets older, thus the types of oil, which would not be deemed a good fit if your vehicle were new, have now become a realistic option.



This is recommended for regular-exploitation conditions, especially if not more than 10.000 km is covered per year.

Here, the act of saving or using cheap types of oil (of unknown manufacturers) is something you should avoid doing because this kind of double savings usually ends up turning into an expense.

Note: making the switch from synthetic to semi-synthetic types of oil (or from the latter to mineral) is NOT obligatory and is only a realistic option for lowering the expenses of older vehicle maintenance.

General recommendation:

After more than 10 years or 200.000 km, a good practice would be to shorten the service intervals by 20% or 30% compared to the initial manufacturer’s recommendation.

Engine oil


For example:

Switch from a variable-interval change schedule (30.000 km or even 50.000 km) to a fixed-interval change schedule (15.000 km), typical for the VW vehicles (Audi, VW, Skoda and Seat).

Switch from 30.000 km to 20.000 km maximum (certain Renault vehicles, PSA vehicles and many others) or 15.000 km (Opel and other vehicles).

Switch from 20.000 km to 15.000 km (certain PSA vehicles, Ford, Japanese manufacturers etc.).

Switch from 15.000 km to 7.500 km (a number of vehicles from the 90s)

For all of the examples above, the time limit should be 12 months. In the case of new vehicles, the interval can be as long as 24 months, but that doesn’t apply to old, high-mileage vehicles (with a lot of engine hours on them). Of course, the examples above relate to maximum-interval schedules, with short-interval schedules representing an even better solution.

We hope that you’ve found this article useful. For any questions, unknowns and suggestions you may have, please, feel free to contact us.

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