its been sitting for 3 years, the previous owner tried cranking it with the old gas, did this ruin the engine???

 

The fuel shouldn't matter if your just trying to start it. Just make sure all your fluids are there, and you have a good battery. If your car doesn't start check the spark and see if its flooded. Then go from there.

One last thing is you may want to do a compression check before you start. You may be trying to beat a dead horse so to speak.