I have to agree with Jim, especially when it comes to the LSAT questions. Remember that the LSAT and the GMAT are different creatures and that a LONG reading passage on the GMAT, for example, is a short passage on the LSAT. However, the GMAT Reading Comp can be a little be denser even though the passages are shorter.
As for Critical Reasoning, there are LSAT question types that are not on the GMAT at all. As an example, there is a type of question where you prove the conclusion as absolutely true rather than just strengthening it. Things like method of reasoning and parallel reasoning that are very small parts of the GMAT are about 25% of all LSAT questions. And of course many LSAT questions rely on formal reasoning, which the GMAT does not rely on.
So, basically you should be doing LSAT questions for learning how to reason/ having fun.
I have written three articles on using the LSAT to study for the GMAT. However, my main advice would be to focus on the GMAT problems from the Official Guides, GMATPrep, the add-on Prep Pack, the verbal review, and reputable sources like Veritas and other companies. If you are using LSAT questions, you should have done LOTS of GMAt questions first so that you are in a position to say - "Yes, this is very similar to the GMAT I can learn something from this," versus, "No, this question would never appear on the GMAT so this is just for fun."
Think of these articles as providing you with guidelines if you do decide to use LSAT questions, while encouraging you to focus on questions written specifically for the GMAT.
https://www.beatthegmat.com/using-the-ls ... 66548.html
https://www.beatthegmat.com/lsat-to-stud ... 69915.html
https://www.beatthegmat.com/lsat-to-stud ... 71361.html