a long time ago, when oil companies started to make their recipes. english car  owners were notified
 not to touch these mixtures...we had to stick to what they used to call then, HEAVY DUTY OILS ( 10,20,30W ) . No soap, no detergents, no chemicals add etc etc. HD was pure ???   Popular Mechanic had an article on these oils that I still memorialize  each time we make and eat  spaghetti...30, 50, oils are  like a really heavy  meat sauce... when you put your spoon in it ( like the tomato juice with the celery ), it does not move ! heat it, it becomes heavier...should be opposite ! ( I know a lot of persons that will  not like what I just mentionned) but if  you add some noodles, more noodles  and  mix them and heat them.. the mixture gets   easier and easier  to mix  and more liquified etc...like 5 in W50, 10 in W30... even my wife did understand this ! I had to say this. because she is wonderful, yes yes yes. Problem is: when you make spag meat sauce, how to you add  and divide to make it 30 ??? 
best regards to Wobbly
pierre 
lac beauport pq
zephyr 85

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