Originally Posted by
owl
I forgot to mention the rings. They may not be seated properly. Before taking it to the dealer change the oil to a regular 5w-30 and then on the way to work rev the thing to 5000+ rpm a few times a day for a week. The low range may be needed. Also try accelerating moderately going uphill. Don't abuse it, by any means but get it under a good load multiple times.
That will force the rings against the cylinder walls and hopefully create a better seal. After a week or so change back to the light oil and see if things have changed. If this doesn't work, you are out of six litres of oil and some time, but if it does, your satisfaction is priceless. I wish you all the best.
I had a 2007 Dodge Megacab with the 5.7 V8. It wasn't until 30,000 miles until it quit burning oil. I had switched to synthetic at the first oil change and it burned a quart every 3000 until I hit 30k. I used a larger filter so the capacity was 7.5 quarts. Oil changes were expensive indeed.
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View my fuel log 2015 Mirage ES 1.2 automatic: 40.5 mpg (US) ... 17.2 km/L ... 5.8 L/100 km ... 48.6 mpg (Imp)