My grandpa wants to get a new ball.  I was thinking along the lines of a jolt pearl, but I don't know that much about different bowling balls.
 
He throws a lot slower than he used to but still gets his fingers into it and the last couple of bowling balls he has gotten have not satisfied his needs (Original X-factor used in x-condition and a new Brunswick Red Zone).  My grandpa likes to stand center dot or right of center but because of his slower speeds these last couple of balls he has gotten he has had to stand all the way to the left. I am not sure how either are drilled, but with the way they reacted he thinks it's just the ball. He favors storm or brunswick bowling balls.
 
The house he bowls at has has a medium amount of oil on the lanes and the shot is typically second arrow. I do not know much about different balls or drill patters. My grandpa used to know a lot about different balls and patterns but with all the new technology out there he did not keep up.

Suggestions for a ball and drilling pattern would be greatly appreciated.

Jolt Pearl should work or Tropical Strom.
I would stick with Jolt Pearl.
I have one great ball!!
If you want to know about strom balls askes me be glad to help.
My Arsenal Paradigm,Ace,Vertigo,Agent,T-Road,Pyro,Thunderstruck Pearl,
Jolt Pearl,Hot Rod Hybrid. T-Road great ball can use on about anything
from a house pattern to shark pattern.
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Mark Vansel