Here's a breakdown of the possibilities:
* Worn Piston Rings: This is the most likely culprit. Worn piston rings allow oil to seep past the pistons into the combustion chamber. This oil burns, resulting in the blueish-white smoke (especially noticeable on startup when oil has pooled), and the loss of compression. Loss of compression explains the lack of power, particularly under load (going uphill).
* Worn Valve Stem Seals: These seals prevent oil from leaking down the valve stems into the combustion chamber. Worn seals can also contribute to oil burning and white smoke, though usually less dramatically than worn piston rings.
* Head Gasket Issues (Less Likely): While a head gasket leak *can* cause white smoke (if coolant is leaking into the cylinders), it usually presents with other symptoms like overheating, milky oil, or loss of coolant. The power loss uphill is less indicative of a head gasket problem.
* Crankshaft Seal (Less Likely): A worn crankshaft seal would leak oil externally, which you've ruled out.
Why it's worse uphill: The increased load going uphill demands more power from the engine. With reduced compression due to worn piston rings, the engine struggles to generate the necessary power.
Diagnosis:
A proper diagnosis requires a mechanic to perform a compression test. This test measures the compression pressure in each cylinder. Low compression in one or more cylinders confirms worn piston rings or valves. A leak-down test can pinpoint the source of the leak (rings, valves, or head gasket).
In short: You should have a mechanic perform a compression test and potentially a leak-down test to confirm the diagnosis. Ignoring this issue will likely lead to further engine damage. Replacing piston rings or valve seals is a significant repair job, often requiring an engine rebuild or at least a top end rebuild (depending on the extent of the damage).
