check compression on each cylinder with a compression test. This is done by removing a sparkplug one at a time, and screwing in a compression tester, turning the engine over by turning the key without starting it, and it will give you a correct psi level that your cylinders are operating at. check in the manual or on here for safe levels, and if they are below the limits, your rings are bad and are allowing blow by (oil to enter the compression chamber and it is burning). if you need more help, post, and i'll give you a more step-by-step set of instructions. hope it helps.
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