What types of additives are there?

These days you can buy a huge range of engine oil additives at parts shops, from all kinds of makers and for all kinds of purposes. The labels are full of exciting promises: your engine will immediately start running quieter and smoother, power will go up, fuel consumption will go down, and oil consumption will stop altogether. Some additives promise extra side effects too, like a complete engine clean-out and so on.

Is all this true, you might ask? Yes, it's true (but only in some cases) – provided, of course, that the additive you bought isn't a counterfeit. That, incidentally, is confirmed by a good many (though far from all) car owners who've used engine oil additives.

At the same time, another large group of car owners is categorically against using engine oil additives and considers them completely ineffective and harmful.

The first group has an ironclad argument – practical experience of using them. The second has logic, car manufacturers' recommendations, and, incidentally, sometimes practical experience too. So where does the truth actually lie?

That's exactly what we'll get into below. Nothing comes for free, and so the key question is: what does using engine oil additives cost you down the line, and how far off is that "down the line"? To answer that, we need to dig a bit deeper into how engine oil additives actually work and how they affect the engine.