Any Japanese engine (and a minority of none Japanese engines) that runs on LPG should have a valve lube system fitted.
Lube systems should be adjusted so that 1ml of lube fluid is used per litre of fuel (1000 to 1 fuel to lube ratio).
If we applied 6 drops per minute to a big engine and applied 6 drops per minute to a small engine we might find that the fuel:lube ratio would be significantly different between the 2 engines because the big engine uses more fuel than the small engine. 6 Drops per minute isn't a bad initial lube setup starting point but from there the system should be adjusted to achieve closer to the 1000:1 ratio.
It isn't always as clear cut as a big engine needs a faster drip rate than a small engine... because vacuum powered lube systems are also effected by other aspects (such as aspects of engine breathing and gearing). In one respect vacuum powered lube systems work counter-intuitively because they allow more lube to enter the engine at light throttle (high vacuum) than they do at heavy throttle (low vacuum) but in mixed driving this doesn't really matter due to the way in which the lube fluid does it's job (builds a protective layer on valves over time). We might expect a big engine to draw more vacuum for a given driving condition (because the driver doesn't need to press the accelerator as far on the more powerful bigger engine) but this isn't always the case because the big engine is more likely to have higher gearing (lower rpm for the same speed which can imply less engine vacuum) than the small engine.
Another way of looking at it - a vacuum powered lube system, given a certain engine vacuum, given a certain level of adjustment of it's flow adjuster, will provide a certain lube flow regardless of the amount of fuel being used and regardless of engine size... 6 Drops per minute is ok as a starting point when the lube system is first installed but then the owner should compare lube usage to fuel usage and adjust the flow adjuster to get closer to the 1000:1 ratio. Because the ratio is so high (1000:1) the owner should expect to need to run a couple of tanks of fuel before making the lube fluid use to fuel use comparison because only 150ml of lube fluid should be used for 150litres of fuel... It would be difficult to check the correct ratio after a trip that only used 20L of fuel because per 20L of fuel only 20ml of fluid should be used (and fluid container in the engine bay might hold 400ml of fluid, difficult to check if 1/20th of a lube fluid bottle has been used).
Simon
