Re: Yanmar hard starting question
Hear hear! 'Concoction' being the operative word. Also, unspecified additives in a new or overhauled engine could void the warranty.
Should the engine suffer damage - whether or not caused by the additive - the ensuing claim could get messy, because we all know that when money is concerned big business and insurers will duck for cover if there is any possible 'out' that can be used to exonerate them or their product.
If the manufacturer wants stuff added, the manual will say so. For example, my Moto Guzzi motorcycle manual suggests a Moly additive in the final drive gear oil. However, it is a fairly old manual for an old-fashioned bike, so if a newer grade gear oil already had a Moly content, I would not be adding any more.
However, if you have an old, worn engine that is burning oil or obviously on its last legs, I suppose it is reasonable to try anything to prolong the inevitable overhaul or replacement.