The CRX I bought had a swap engine but how can I find the mileage for the engine? Is there some kind of code to look up online?

 

No way to find out the exact milege

 

How can I estimate the mileage?

 

Ask the previous owner what the milege of the car was when the new motor was installed.... Then ask him how much milege the new motor had

THen you can get an estime of how much miles were put on the new engine.

Thats about the only way i can think to do it

 

Besides obtaining the cluster from the engines original car there is no way to get the exact mileage or een a good estimate.