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I've been using mobile one 0w20 . It is a 6 speed. Just inspected the undercarriage and can't find any sign of oil anywhere. Still looks new underneath. A friend told me I should start using the sea foam spray to help keep the intake valves clean. Is this a good idea? Have noticed when at a stop light under load the center console shakes and my water cup vibrates to the point water comes out of the cup, could this be because of dirty valves?

Thanks, I do drive mostly hwy miles and probably in v4 mode alot. My service manager told me they fixed this problem in 2015 and he hasn't seen one use oil since the 14 model and and a quart to quart and half loss wasn't a big deal. Having to add oil in between oil changes on a new truck doesn't seem normal to me. Is this something that could get worse once my warranty runs out?

I recently purchased my first GM vehicle, a 2017 Sierra with the 5.3l. Purchased from a local GMC dealer in August of '18, with 18k miles on it. At 22k I had to add a half quart of oil, thought maybe dealer didn't fill oil properly. At 24k I changed it myself with 8 quarts of 0w20 and ac delco filter. Just checked the oil at 30k and is barely showing on dip stick, no leaks in driveway. Took it to dealership and they started an oil consumption test. Service manager said they put in 8.5 quarts instead of 8. Said he wanted the oil to measure at the top hash. When I got home on level ground I checked the oil after sitting for half an hour and the oil was a quarter inch above the top hash. Is this normal procedure and how do they measure the oil loss when I come back 1k miles later?