Whatever oil you use, your Mid-Size Ranger engine still might need to be rebuilt and have parts replaced. Places like Indy Speciality can do it for around $2,500 -- provided that you trade in your own core. But if you want to save some dollars, it is possible to rebuild your Mid-Size Polaris Ranger engine yourself. The crank and bearings will set you back $650-$700 and the jug pistons / rings go for around $250. It’ll take less than an hour to have the motor out of your machine and on a bench. You can get the service manual from your local dealer which has step-by-step instructions as well as every torque specification and other specs you’ll need -- but don’t forget the valve guides as well.
Like engine rebuilds, bore kits are also popular engine mods to up the HP of your Mid-Size Ranger. Companies like Alba and Millennium Tech Kit offer 602cc bore kits with claims of up to 25% horsepower increases. Many riders feel like bore kits are a waste of money, where a cam swap and ECM flash can give comparable results. But even a gain of only 4 horsepower is nearly a 10% gain, which is hardly unnoticeable. So if you need an engine rebuild anyway, it might be worth the extra cash to get the big bore on your Mid-Size engine.