Odds are on your side that the damage will be minimal.
Not a gamble that I would take as replacing an engine is a lot more expensive than $20 of oil.
Not one gasoline car or truck company ever recommended the use of diesel engine 15W-40 engine oil in their motors. Diesel engine oil has higher levels of zinc and phosphorus. which will shorten the life of the catalytic converter. When the ambient temperature drops lower than +10 Degrees your starter motor will not spin the crankshaft as the oil is way to thick.
Given the mileage, it may be OK, not really smart though. Clearances on modern engines are tight. Doesn't really sound like you are going to change it until mid-December, but do it then.
It depends on where you live. Here in the Yukon, we need 0w30, or maybe 5w30. If it's warm where you are, you should be okay.
Heavier weight oil can affect the variable valve timing mechanism causing misfires and excessive wear. Drain ASAP and install the proper oil. Read these two posts on what can happen when you screw around with oil viscosity.
http://ricksfreeautorepairadvice.com/mot...
http://ricksfreeautorepairadvice.com/wha...
15w40 is rather heavy for use in Fall/Winter months, especially if you are traveling in areas with temps at or below freezing.
Not ideal but it would work in a pinch.
Ok so I have a 2006 Chevy Cobalt with a 2.2L ecotec engine with 183k on it that calls for 5w30. I had a gallon of 15w40 in the garage so I changed the oil in my car with it, my question is will my engine be ok with that oil? I'm probably going to change it again around Dec. 15th when I get paid before all the Christmas traveling.
