There are so many different ideas about what oils to run a person could get dizzy from all the conflicting information. Personally I run thicker oils in my vehicles. I have run 20 50 in lil Suzy since about 93, I bought her in 91. I also always run synthetic oil.
First let me say that I am not a novice at this. I grew up around cars, my uncle who owns an automotive machine shop, where I worked while I was in High School, built and raced stock cars for many years. I built and raced hot rods from the time I got my license until I was in my late 20's.
Here is why I think thicker is better.
First, as was stated earlier most wear does happen at startup. The idea that you want a thinner oil so that it will pump the oil to the bearings faster is a flawed idea. First the oil pump will pump any weight motor oil at the same speed. An oil pump is a gear pump and it is going to move the same amount of oil whether it is 0 30 or 20 50. as a mechanical device it can not change speeds and does not bog down because the oil is thicker.
Second, Thicker viscosity oils stay in contact with the wear surfaces longer than thinner oils. This is what you want, You do not want to have the oil pump quickly push oil to the bearings, you want their to be oil already there to lubricate the bearings until the oil pump oil gets there. Also, you want the oil to stay in the oil gales so the oil pump only needs to pressurize the oil which is already there instead of having to pump the oil up out the pan.
Third, When you are working an engine as hard as we are these little Suzukis under high torque conditions a higher viscosity oil will protect bearings better than a thin oil which can allow the crank to contact the bearings in high stress situations. There is a huge difference between the stress on an engine leaving a traffic light and what it takes to force a tire up the side of a 3 foot boulder.
While I am on this kick, (pun intended) stay away from standard multi weight oils. first of all an oil, say 10 30 is suppose to be 10 weight when it is cold and 30 weight when it is hot. This is not physically possible. The actual numbers are closer to 18 22. The reason that the oil thickens at all when it gets hotter is because the formulation contains a form of synthetic rubber molecule which expands as it gets hotter. The problem with this is that these molecules turn to carbon if they are heated above about 300 degrees. This means that if you have a coolant problem there is a good possibility that you will ruin the engine. This will not happen over night but the carbon which is now in the engine circulating with the oil is just like sand paper. it will get into the rings and bearings, valve train etc. and cause major wear. The only way to get rid of carbon in an engine once it has been overheated with conventional multi weight oil in it is to tear it down and completely clean it. This means stripping it down to the block and having it run through the hot tank at your local automotive machine shop.
Synthetic oils use a different chemistry to achieve viscosity change so it will not carbonize when it is heated. Although for the record it does not change the actual viscosity much either.
Lastly if you look in your owners manual you will find that 20 50 oil is recommended for a Suzuki 1.6 8V engine down to 30 degrees F. I run 20 50 year round in lil Suzy and have not had any troubles. I live in Colorado so there are some cold days. When I crank her the oil light is out by the time she fires so I know there is lubrication getting to the bearings. I am also confident that the thicker viscosity oil is staying on the oil rings and not running back into the oil pan, providing cylinder lubrication at startup.