At 162k miles my XL-7 ran powerfully without smoke or any oil use (fresh "synthetic" 5w-40 in it).
Then I serviced the timing chain, valve covers were taken off and stored upside down, probably liquefying characteristic sludge in PCV of which I did not know at the time.
After completing the work and driving ~15 miles, the very next morning it started blowing a cloud of smoke.
This continued happening on first cold start of the day. After driving in town at slow speed for a while and then accelerating, it would ping and blow blue smoke, so I'd give it little throttle until ping mostly cleared up, then italian tuneup for 3-4 seconds and then it ran beautifully again. I quickly learned to simply step on it from stops. One consolation of XL-7 is that it rips down the road like nobody's business :-)
It would suck up 1 quart per 150 miles. I basically carrier a gallon of oil and topped it off at every 1/2 tank fill-up.
Having prior experience with Suzuki's valve seals leaking synthetic oil, after the 1st gallon I changed oil to "high-mileage" unsynthetic. 2000 miles later changed it again. 2000 miles later cold-start smoke decreased to a little puff of blue instead of a smokescreen. ~500 miles later it was not smoking on cold start and oil consumption stopped. Oil level stayed at the same 3/4 level over 3 fill-ups, so I topped it off to the full mark. At another fuel fill it was still exactly at the full mark. So total of 2 oil changes & 4500 miles and it's due for another one. Dipstick wipe still looks "clean".
It was a good opportunity to check the spark plugs and they were heavily baked over with oil ash, the ceramic-like gray hard rock that withstands scraping with a screwdriver. Stock IFR5j11 plugs. Sparking electrodes were still clean and bright - they didn't misfire and the engine started on first crank pretty much instantly. In fact with PK16pr11 it takes a moment longer to cold-start.
Conclusion of the story is to never remove the valve covers, or else drill the PCV drains while they are off. And always keep oil fresh, like 2k-3k miles at the most. Suzuki V6 are weird engines.
Did you ever find out what causing those issues for you?
I have been driving a 2002 XL-7 with a 2.7L V6 with about 222,000 miles and it suddenly now in the last month or so started blowing blueish smoke on start up and it's upsetting to see.
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