Chrysler Repair: 2002 jeep liberty: oil consumption, worn piston rings, combustion chambers

Question
hi, i own a 2002 jeep liberty and it has a high oil consumption and emits a kinda blue smoke when driving slowly and when parked

Answer
Hi Esther,
Blue smoke is the other aspect of high oil consumption: the oil that is consumed is as the result of oil entering the combustion chambers of the engine and being burned. It can be due to worn piston rings or leaky valve seals. A test, called a leak down test, can be done to determine which is the cause. If it is the piston rings then that involves removing those and putting on new rings which is expensive; if it is the valve seals it requires removing the seals and replacing them (which are located in the cylinder heads) but can be done without removing the heads, which is less expensive. You can reduce the amount of oil used by changing to a higher 'weight' of oil by one or two steps higher number than what you are using now. So give that a try the next time you change oil. Tell me which oil type you are using now.
Roland

PS: Both types of wear that I listed cause a reduction in the compression of the fuel/air charge in the combustion chamber due to leakage. The classic test to distinguish rings from valve seals is to remove the spark plug and insert a compression gauge to measure this pressure. You measure it two ways: just as it exists and then again after adding a teaspoon of oil to the chamber thruough the spark plug opening. The oil flows down and around the piston/cylinder wall interface and thus will improve the 'seal' and raise the compression reading IF the problem is due to worn rings (the 'leak down' area); whereas if it is a leaky valve seal problem the reading will not change because the oil will not flow to that area of the combustion chamber (above the spark plug opening). So it is a very quick diagnostic test that needs only a compression gauge and takes a few minutes to perform.
Thanks for the evaluation and nomination.