Small Engines (Lawn Mowers, etc.): oil consumption, viscosity oil, combustion chamber

Question
I have a 17.5hp Tecumseh engine on a lawn tractor about 5 years old.  We have moved this year and have a larger sloped 2 acres to mow.  I have had to add approximately 4 oz. of oil after mowing the lawn which I have never had to do in previous years.  Yes, the engine is working very hard on the high angle, but is this oil use normal?
Thanks for your time,
Paul

Answer
It sounds like it may be a combination of the slope itself allowing oil to enter the combustion chamber via the valve guides or PCV and working hard.  You can't do much about the working angle but if the engine is getting very hot due to the load it is under, I would recommend switching to a quality synthetic 10W40 (or even 20W50) oil.  I would never use a higher viscosity conventional oil but the synthetic flows much better at lower temperatures and has better thermal properties so you can use a higher viscosity.  Air cooled engines rely on the oil for cooling as well so a poor quality, high viscosity oil will not flow through the engine efficiently and will not aid cooling very well.  As for whether this much oil consumption is normal, it really depends on the number of hours on the engine.  Hope this helps.