I have a question regarding the oil in my wife's '07 Outback. 5000 miles ago, for the first time since buying the car (used, about 5 years ago), my wife took her Outback for a service to somewhere other than a Subaru dealer. It's out of warranty and she'd heard of someone who specialized in Japanese cars. He told her that the 5w30 oil that Subaru use is terrible and he would put something much better in instead. Tonight, my wife asked me to check the engine oil level. It was below the empty level on the dipstick, but just barely registering something. This car has never burnt through oil before, so I looked under the car, expecting to see a leak but, nothing. I went to the store and added 2 quarts of semi-synthetic 5w30 and that topped it off, so I guess it can't have been completely empty.
My wife showed me the receipt from the guy who serviced her car and it says he used 20w50 oil. So, my question is, would using such a different weight of oil from the manufacturers' recommendation cause it to burn off so quickly? Or is it more likely something is wrong with the car? She's gonna' take it back to the same guy tomorrow to have him check it out, but I'm curious to hear opinions from people who aren't taking money from me/my wife. Thanks.