how is synthetic 5w30 thinner than regular 5w30?
When it hits running temp, it get thinner than conventional oil.
Wow, I thought I had heard all of the myths about oil, but that is a new one!
Your statement is incorrect, as the viscosity of synthetic oil does not get any thinner at running temp than conventional oil. What makes synthetic oils superior to conventional oil is the fact that they maintain their viscosity better. In other words, a 5w-20 conventional oil as it ages will begin breaking down to it's base stock of 5w. Meanwhile, a synthetic 5w-20 oil after the same amount of miles will remain roughly the same 5w-20 viscosity rating.
With some reported exceptions, the 4 cylinder version of the Cherokee is known as an oil burner. If I owned one I would only use full synthetic oil, as conventional 5w-20 as it breaks down to 5W is more likely to burn away and lead to increased oil consumption. For that matter, I would run synthetic 5w-30 in it to further help the oil from breaking down. The only reason 5w-20 oil became a thing in the first place was to squeeze a tiny bit more mileage out of the engine. But in reality, any car that uses 5w-20 would run perfectly fine with 5w-30 and it would help reduce oil consumption in cars that experience it with 5w-20.
