3. The type of lane machine used to apply the lane oil - Older machines apply oil using pads that wick the oil, but newer machines are more precise, using either injectors (Brunswick machines), or "sanction technology" that works much like an ink jet printer (Kegel machines). Each type produces slightly different results. Also, older machines can only apply oil going down the lanes (forward) while the pattern may also specify reverse oil, so the pattern will play quite differently without the hold of that reverse oil.
4. Whether this is the first time (or second, third, etc.) the pattern was placed on the lanes - Bowlers believe that the lanes have "memory," such that you may encounter hints of the prior pattern the first time you play on a new pattern. If the prior pattern was a house pattern, which was often the case, those hints will likely make the current pattern play in a quite unexpected way. Bowlers believe that the pattern becomes "truer" with each subsequent application to the lanes.
5. How much time has gone by from the time the oil was applied until bowling started - Oil is affected by gravity. The more time that has gone by, the more the higher concentrations of oil will have bled into the adjacent areas of less oil.
6. Whether it was warm or cold overnight inside the center, and whether it is humid or dry inside the center - Oil will tend to be less thick on warm lanes and will evaporate more quickly. Oil will also evaporate more quickly if it is dry in the center. Oil that had been stored in a cooler area of the center before being applied will be thicker, however.
7. Most important and yet very basic, whether the lane machine was operating properly - If not, more or less oil may have been deposited at one or more points on the lane. Even worse, it can happen that the machine did not strip off the previous oil before applying the new oil. Or that the machine stripped off the old oil but never put down the new oil. And then there's the possibility that the machine was actually operating properly but put down the wrong pattern, either because the lane mechanic misprogrammed the machine (easy to do) or was told the wrong pattern. Any of these things rarely happens, and while the center will usually re-oil once it finds out to correct the situation, you cannot assume that will be the case.
From LANE to LANE:
8. The tiny hills and valleys in each lane's lane surfaces (technically referred to as topography) - Lanes are required to meet specifications set by the USBC, and yet, minute variations allowed within the specs may still provide advantages to some bowlers and disadvantages to others. This is why many tournaments make you change to a different pair of lanes after each game in the qualifying squads - to create a more even playing field.
Oil pattern sheets are quite precise, which ought to mean that you can count on an oil pattern playing exactly the same each time. AND YET... many factors conspire to make this highly unlikely.
Factors from CENTER to CENTER:
1. The type and age of the bowling pins - Your ball may go down the lane in exactly the same way at two different bowling centers and yet one shot will strike while the other will not. Pins take a beating (literally!), so older pins tend to have more rounded bottoms and may fall more easily as a result. Also, pins made of plastic ("Twister Pins" is one brand name) will likely fall differently from the more common traditional wooden core pins.
2. The type and age of the lane surface - Your ball will tend to hook more on wood lanes than on synthetic lanes. On synthetic lanes, the degree of hook will depend upon the brand of lanes installed. Brunswick Pro Lane generally provides the least friction (least hook) and AMF SPL provides the most friction (most hook), with other brands in between. Older installations of any brand will tend to provide more friction (more hook) than newer installations. And, it could be that the bowling center installed the front panels of the lane more recently than the back panels, or vice-versa. Even more challenging, the center may have had to replace individual damaged older synthetic panels with new ones; for example, one in the front on lane 12, another halfway down lane 25, and another in the backend of lane 32. The bowling center staff on hand at the time will likely not be able to tell you which ones had been replaced.
And even from GAME to GAME:
9. The impact of carry down - As bowling balls rolled take up oil in the front of the lane, they leave traces of it, or carry down, on the originally dry backend of the lane. The change in the oil pattern from from game to game (and sometimes even frame to frame) is referred to "lane transition." The next pair of lanes may have transitioned differently if the previous bowlers used more or less aggressive bowling balls. This is why it is a good idea to keep an eye on where bowlers are playing on your next pair of lanes, especially a bowler whose game is similar to yours.
For these reasons, you should always pack your bowling ball bags being prepared for the unexpected. The best bowlers are the ones who let their bowling balls tell them which bowling balls to use, not the oil pattern sheet!
With an appreciation of all of the reasons above why an oil pattern may play differently than it shows "on paper," you are now ready for an Advanced Understanding of an Oil Pattern Sheet.