This is because brake fluid is a hygroscopic fluid - meaning that it absorbs water over time reducing its effectiveness.
If the fluid is not changed before the water content reaches the 3% mark, the water brings down the normal boiling point of the brake fluid and air bubbles are created as a result. Once this happens, the brakes become ineffective and dangerous.
If that wasn't bad enough, a motorist probably won't even be aware that this has taken place because the braking system will appear completely normal until the brake fluid reaches the reduced boiling point - which usually occurs after braking heavily.
Symptoms can be:- the brakes take on a sponge-like feeling and don't work - so the car fails to stop. If the driver happens to be on a hill or driving along a motorway when this happens, the consequences don't even bear thinking about.
For this reason Renault recommend your brake fluid is replaced every 4 Years or 72,000 which ever is sooner.
Your engine coolant has rust inhibitors and ethylene-glycol in it, which provide efficient cooling and freezing protection of your engine throughout the year not just the winter!
However over time these properties naturally deteriorate and require changing to ensure the reliability of your cooling system.
For this reason Renault recommend your coolant is replaced every 4 Years or 72,000 miles which ever is sooner.
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