A The accepted standard for "normal" oil consumption is a maximum of one quart per 2,000 miles. So the oil consumption on your daughter's vehicle is high but not necessarily excessive. Depending on the engine's mileage, it's borderline. GM doesn't recommend any type of engine flushing and, of course, engine flushing isn't going to fix worn parts like valve seals, piston rings, etc.
I'd try treating the symptoms first. Adding a half-can of SeaFoam to the oil can help free sticky oil control rings and dissolve carbon and varnish from oil residue. Using a different brand or higher-viscosity multiweight motor oil, particularly in warm weather, may help reduce oil consumption on a higher-mileage engine. Full synthetic oils will lower oil operating temperature and may reduce consumption.
Q I have a 1970 VW Bug with an add-on external oil cooler and 20,000 miles on a new (not rebuilt) engine. It runs cooler on multiweight oil than with straight 30-weight, But with so many varieties of oil on the market, which is best?
A Air-cooled engines are also oil-cooled engines, so a synthetic multiweight oil would be an excellent choice to control oil temperatures.
Q Settle an easy question: What was the old General Motors "pecking order" from least expensive to most expensive? I say it was Chevy, Pontiac, Buick, Olds, then Cadillac. My buddy says it was Chevy, Pontiac, Olds, then Buick, then Caddy.
A That's not an easy question. Before General Motors, Ransom Oldsmobile and David Buick were building cars before 1900. Billy Durant formed GM with the purchase of Buick in 1903 and Oldsmobile in 1909. He also added Cadillac and Oakland Motors (which became Pontiac) that same year. And finally, Chevrolet was added in 1916. By the end of the 1920s, each GM "brand" had is own marketing and identity.
I'm not sure it's possible to identify an absolute pecking order for GM vehicles, but by the late 1940s, several different automotive platforms were in production. The more expensive "C-body" was used for Cadillacs and Oldsmobiles and eventually for higher-end Buicks. The less expensive "A-body" was used for Chevrolets, Pontiacs and lower-end Oldsmobiles. Even at this stage, there was a great deal of "sharing" among GM brands.
By the late 1960s and into the 1970s, Buick, Olds and Pontiac shared many of the same platforms, so the "B-O-P" moniker applied to many chassis, engines and components. Perhaps that was an insight into today, where only Buick survives along with Chevy and Cadillac as the GM car brands.
So was it Buick, then Olds? Or Olds, then Buick? I guess it depends on which is your favorite. I lean toward Buick as the more prestigious brand. My dad drove a '41 Pontiac until the mid-1950s; then we had a succession of Buicks until he could afford a used Cadillac in the early 1960s.
There was a '68 Pontiac Catalina in there for a year or two, but he never liked the car so it was back to Cadillacs, including his last -- a 1972 Sedan DeVille. In fact, I took my driver's test in our '59 Sedan DeVille, a leviathan of an automobile that made the parallel parking test a real challenge. We figured out a clever way to make sure I parked between the white lines -- but that's a story for another day.