I have a 1998 Volvo S70 with 140k. 2.5 litre 5cyl automatic. For sometime now my lifters have been making noise especially at start up. I’m up to date on my oil servicing using Volvo filters and a 20-50w motor oil ( as recommended by my mechanic ) but still the noise continues. In the past I have used additives to the oil but still the problem continues. Maybe I’m using the wrong one. Can you recommend an additive?