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post #16 of (permalink) Old 01-07-2017, 08:57 AM
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When I say "vacuum", maybe I'm using the wrong term. But what I mean is that when you are full throttle, surely there is more "suction" at the throttle body opening than there is under light throttle? I mean way more air is being sucked in, so I would think that there is a better chance of oil to be sucked in as well?

Like I said, I have no evidence this is try, just seems to make sense to me...

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post #17 of (permalink) Old 01-07-2017, 09:16 AM
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Vacuum (which operates the pcv) is at its lowest during wot due to the open throttle plate. Vac. is at its highest during deceleration due to the closed throttle plate and still elevated rpms. To determine a healthy engine using a vac. pressure gauge you want to see ~20 in. mercury @ idle at normal operating temp. A/c engagement will lower the reading. Another good test is the snap throttle. At idle, rev eng. momentarily and vac. gauge should nosedive to ~0, then spring back up to ~25 and settle back down to ~20. For other gauge scenarios/readings, there are vac. charts all over the web with symptoms/causes. The simple vac. gauge is becoming a lost art in determining eng. health....

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post #18 of (permalink) Old 01-11-2017, 08:28 AM
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Originally Posted by kb3gup View Post
Hey guys,

Just wondering what kind of gas mileage are you getting in your 8th gens? With stock tune? And if you're running top tier gas? And any other considerations like excessive oil consumption (some cars seem to really drink the oil through the PCV and back through the intake and some don't at all thus don't experience the carbon issues and reduced gas mileage like other do). Also if you mostly if you do city or highway driving. I'm getting about 16 town 20 highway top tier 93 octane which is up a few miles after replacing the evap purge solenoid and the canister vent solenoid which were both bad. Mine drinks a lot of oil and I'm wondering if my mileage has decreased enough that I can get the dealer to do a manual cleaning of the valves under the powertrain warranty. The normal $100 deposit won't cover them telling you whether or not it will, so I'm fishing for evidence. Thanks!
My 2016 is running the stock tune, and I've been averaging 24 mpg running Tier 1 (mostly Chevron; some Shell) regular 87. This is with 80% freeway and 20% surface street driving, but my freeway drives are almost all during rush traffic, with lots of stop-and-go / creep-and-beep going on. I've been very happy about this mileage, because the car that the Impala replaced never returned better than 22 mpg with exactly the same usage on the same roads, despite the old car being a couple hundred pounds lighter and having a much smaller motor with far less power.

I have put about 1500 miles on the Impala since buying it and have not noticed any oil usage. I have not yet changed the oil from whatever was in there when I bought the car, but will be putting Mobil 1 5W30 in the crankcase when I do.

Cheers! Impala Limited LTZ
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