Smoky Isuzu

[Moon Shadow]

I have had a lot of service work done to the engine in my HC38 MKII, Isuzu 50 HP, 4 cylinder. Mostly servicing to make up for the lack of maintenance by the previous owner. The engine had been running ok but there was evidence of leaking pumps and the like so I had both water pumps rebuilt, all hoses and belts replaced, alternator cleaned and tested, new injectors and all fluids changed. The compression was tested and found to be good on all cylinders.
The new oil is 15w-40w. Since it was replaced, I have noticed a lot more oil use (a quart every 20 hours) and I'm putting out more exhaust, presumably from oil. Should I be using heavier oil, maybe 40 or 50w?
I welcome your suggestions.
Glen

[ken_w]

What color is the smoke?

[Moon Shadow]

[pippin]

I have an Isuzu C-240 in my 1978 38-T. The factory recommendation is 30 weight oil.
Mike