OK, over Summer, some houses take shortcuts by not stripping the old, and not adhering to a regular oil schedule. This is common because of the lighter use that lanes receive.
An over application of oil without stripping will yield an erratic play and read. The back ends will vary each time they do it, and it will not be consistent.
If you found a favorable line, consider yourself fortunate. It's often not fun to bowl this way.
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Storm - Shift 16# Medium Length
Legends - Conqueror 16# Heavy arc
Brunswick - Scorchin Inferno 16#, Med-Heavy oil
Legends - Terminator 16# Heavy length
Legends - BigRBang 16# Medium Arc