What you have to consider is what problem is flushing designed to cure or prevent?
With old fashioned mineral oils with low detergent and suspension properties, combustion products wouldn't necessarily be cleared from the engine and held in suspension adequately. So, a product with a higher solvent power could be added to the oil and that would remove the products of combustion from wherever they might have ended up. My personal preference with these types of engine is to use a dedicated flushing oil that will not only clean the engine, but that which has been cleaned from the engine is held in the flushing oil and this removed from the engine. Just putting a flushing additive into engine oil that might have been in the engine for some time is of limited benefit if the ability of the oil to hold the cleaned material in suspension has been exceeded - which is the point of changing oil in the first place.
For instance, with my 1966 Aston Martin, I use Duckhams 20w50 Multigrade mineral oil - as recommended by the manufacturer. I do flush the engine occasionally, but as the oil needs to be changed ever 1500 miles (really), it's usually pretty clean.
The problem with flushing oil in a modern car designed for modern fully-synthetic oils is that modern oils are already extremely agressive as clearing combustion products from the engine. Also, the most complicated material you'll find in a 1960s engine is paper and cardboard, whilst a modern engine is full of various exotic materials that contribute to the robustness and reliability of modern engines. These materials are often immersed or bathed in engine oil and have to react in a predictable way to this exotic mix of chemicals. Change the chemical brew and these seals and gaskets can react in unpredictable ways. Often I've cured an oil leak in a customer car by simply draining out the "performance" oil that he's put in it and putting in the oil that the manufacturer originally designed it for. And, don't get me started on Castrol GTX and Alfa Romeo Variatiors. For some reason, they're just incompatible with each other.
I would never flush a modern engine's oil system when the car had been adequately maintained. In the case of a vehicle that had the same oil in for an extended period of time, where the suspension properties of the oil have almost certainly been exceeded, then, there may be some benefit. However, even then, I'd usually recommend that the correct oil be used, and simply changed once it had an opportunity to scrub the engine and absorb any contaminants - say 1000 miles.
Flushing the fuel system occasionally, however, may have some benefits. All sorts of crud builds up in that!
As regards Maserati recommended servicing operations, some are actually against the recommendations of the component manufacturer.
Finally, if you're wondering how an additive can increase the compression in a cylinder by 10% - as mentioned at the start of this thread - when it should make no difference at all, then consider this. With old and thick oil, there will be increased resistance to cranking. Clear out the thick oil, or thin it out with an additive, and the engine will turn over faster when being cranked, improving gas flow, reducing pumping losses, and thus increasing the apparent compression.
As ever, I'm always open to suggestions!
Mike Roberts
www.maseratished.co.uk
www.facebook.com/maseratished
