My car has 138,000 miles on the clock and I believe I have looked after it well enough for it to do the same again. A rear cam seal leak has been diagnosed and a local, small garage recommended the first course of action to be the use of an oil additive which acts as a 'seal conditioner'.

I trust this mechanic and he stands by this product from a major reputable company. He said if this didn't work, he'd remove the gearbox and replace the seal directly.

Having got home and done some online research, I have discovered that their is a lot of opinion to suggest that these products are a bad idea and may be responsible for future engine and seal damage.

The leak stopped within 2 days. I know my car is old but it has never needed anything more than routine replacement of worn parts, routine maintenance (which I have not skimped on) and one EGR valve. I run it on V-power diesel on your recommendation and what to see how far it will go.

Am I right to worry or is this a reasonable course of action? Does the oil need changing? Should the original seal be replaced (have we only addressed the symptom and not the problem)? Should it just be observed now?