Just before my most recent oil-change, I noticed my car's "check oil level" warning coming on when I would start my car when it was pointed downward on an incline. I was, indeed, at the "add a quart" level. A day or two later, when my mechanic was changing the oil, I mentioned this to him, and he suggested that, instead of using the 10w-30 oil that one is supposed to use in a 2001 Buick LeSabre custom, that I try using 10w-40 oil for the remainder of the summer, hot months.
"The parts of the engine get worn, over time, and the thicker oil will tend to fill in some of the slightly larger gaps."
My mechanic's FATHER--they are a father and son in business together, and both extremely good, smart, seasoned, old-fashioned mechanics, who love cars--overheard this, and objected. "I wouldn't put 10w-40 in that car; in emissions school they told us not to--and it will sludge up the engine!"
This was the first time I heard them disagree about such a matter, but the son said, "It's what I would do for my own car," and went ahead to add 10w-40.
My 2001 Buick LeSabre custom has about 133,000 miles on it. Since my oil change, I've come accross a number of remarks, on line, from people saying that "down a quart" in about 3000 miles is not at all to be regarded as problematic. (I have always had an oil-change quite regularly every 3000 miles).
My question is: Who is right? Albin, the father, or Justin, the son? Could it be somewhat HARMFUL to disobey GM's engineers and use a heavier oil in summer? Will it "sludge up" the engine, as Albin suggested? Or, as Justin suggested, in warmer months, might the heavier oil be less likely to burn and be more likely to keep the engine well-lubricated longer?