| The factory can finish hone the cylinder walls either fine or coarse (rough). This not a case of "bad" or "cheap" manufacturing but, rather, a decision based upon good and bad points of each finish. Fine finish cylinder walls hold less oil on the wall surface and seal better but are hard on piston rings and cylinder walls due to increased friction of a larger ring surface contact area. Rough walls hold more oil and have less surface area (lose less hp to friction) but tend to burn oil. NASCAR and Formula 1 cars tend to have rough walls so as not to lose hp and oil consumption is not an issue. Various car manufacturers adopt different philosophies as to cylinder finish. In reality, from the owners standpoint, a fine or rough finish doesn't really matter as long as the finish applied is the one the factory actually wants applied. You can get around most of the poor points of each finish by the use of different recommended oils (weight and/or synthetic) ring surface treatment, ring composition and tension. Further, the cylinder wall finish (and its effect on oil recommendations) also effects most other internal oil lubricated components (such as the factory finish on camshafts; cam followers; and bearings). It should be noted that emissions certification mitigates against a rough cylinder finish (despite the certain advantages of a rough finish for longevity and hp) as oil blow-by is counted as a hydrocarbon emission.
For myself, I think that factory recommendations are less important after things have worked in about as much as they will over the life-time of the moving parts.
I am a big synthetic oil user (on both cars and motorcycles) but would ALWAYS follow the factory recommendation through the first 5,000 miles or so. If you think that you know more than the manufacturer through the break-in process you are a fool. THEY are the one's who have to pay the warantee claims so it is in their best interest to recommend oil type and weight at least through the break-in period. After the break-in period other factors come into play such as "rebates" and "charge-backs" from oil companies to the car producers to recommend their oil products for extended use (see Corvette/Mobil 1).
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