Oil additive supplements have no place in today’s engines and could invalidate a warranty, an industry expert has warned.

Adrian Hill, automotive product manager at leading oil blender Morris Lubricants, urged car owners to resist the temptation of buying an off-the-shelf additive supplement in the belief that it will help the engine to perform better.

“The idea that you can add a little bit of extra additive into a car engine to improve things is a complete and utter fallacy,” he said.

“All you’re going to do is end up ruining a perfectly good oil formulation.

“When you buy five litres of engine oil, whether it’s Morris Lubricants or any other reputable brand, the formulation in there has been developed extensively with bench testing and field trials to achieve certain performance levels.

“The chemistry has been very finely balanced to meet the specifications of the OEM. That product is all that engine needs for its service life. You can’t improve upon that because hundreds of thousands of pounds have been invested in developing that formulation to optimise the performance of that engine between service intervals.

“If you dollop some additive supplement in there, all of that technology becomes unravelled. It’s like having a really nice cup of coffee and putting a teaspoon of salt in it.”

Adrian said that warranties could become “null and void” if an OEM calls for a specific engine oil and then an additive supplement is added.

And he said that additives could damage components and reduce the life of the engine.

He said: “In modern engines there are after-treatment devices incorporated to clean up the emissions leaving the exhaust pipe. These rely on the correct lubricant being used so that their efficiency is not reduced. If you put an additive supplement in there, it may not be catalytic converter friendly or diesel particulate filter friendly and it can become a very expensive exercise to have them replaced.

“You think you’ve paid a few quid to increase performance, but if you’ve got an engine that requires a low or mid-SAPS lubricant with after treatment devices, you will damage those expensive devices at costs of thousands of pounds. Additive supplements do not have a place in Euro 5 or Euro 6 engines, or even prior to that.”

Adrian said that additive supplements can be used successfully to boost an engine which is nearing the end of its life or in the classic and vintage market.

But he added: “The additive supplement was always a sticking plaster for a mechanical problem. If you’ve got an engine that is burning oil and creating smoke because you’ve got worn compression rings, the addition of a supplement that thickens the oil up to stop it getting past the rings is only a short term fix. You’re only putting off the inevitable that you need new rings and possibly a re-bore. Additive supplements were only ever a temporary measure.”

Morris Lubricants is a British company that has been manufacturing lubricants in Shrewsbury since 1869. The company is now manufacturing more than a dozen passenger car engine oils. Even as recently as 2005, that figure would have been as low as two or three.

The company has recently launched WHATOIL? – which can be found at – as a user-friendly internet-based system which advises the correct product simply by entering a few basic details.