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Old 08-30-2017, 12:13 PM   #1
Dad's72
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2015 Silverado LTZ

Hey y'all. I recently got me a 2015 Chevy Silverado LTZ Texas Edition. I have final put a put a few miles on it and it is time to change the oil. My question to any of y'all who have or do own this model of truck is this. I would imagine that the previous owner and dealership probably used conventional oil on this truck would I do it harm by switching to synthetic at this point in the game? It has exactly 40K miles on it as I type. I was reading that by switching to synthetic oil and draining the differential and putting synthetic in there I could gain mpg. I get pretty decent right now. I average 19.5 in the city and when I took it out of town on the highway I got 22 mpg on that tank.
Also one other question. I see that they put in a 200 degree thermostat from the factory. Would it hurt to go to a 180?
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Old 08-30-2017, 01:14 PM   #2
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Re: 2015 Silverado LTZ

Do not switch to a cooler T-stat. These rigs have a 200 degree T-stat for a reason. The modern engines of today run more efficient at a slightly higher temperature than the engines of yore. You'll do more damage than good.

Gary
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My 1972 GMC 1500 Super Custom (Creeping Death) "long term" build thread.

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Remember Murphys 2nd law of mechanical relationships... "OPPOSING COMPONENTS ATTEMPTING TO OCCUPY THE SAME SPACE, AT THE SAME TIME, GENERALLY END UP OCCUPYING ADJOINING SPACE AT THE BOTTOM OF THE OIL PAN"
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Old 08-31-2017, 09:19 AM   #3
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Re: 2015 Silverado LTZ

Crazy. Seems counterintuitive but that is why I asked. How about switching to synthetic in the motor and rear end? Any input from any of you guys? I plan on changing my oil this weekend and have been thinking about it. Which synthetic oil would y'all recommend?
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Old 08-31-2017, 10:10 AM   #4
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Re: 2015 Silverado LTZ

How many miles???
Any of the name brand synthetics are fine to use. Even the house brand at Wal Mart, HoReilly's and NAPA are usually bottles by Ashland, the company that makes Valvoline. Use a NAPA or Wix filter.

You need to find out if the rear end is a posi, if so, do NOT use synthetic it it. If it is a posi use a name brand 80w90 in it with the GM posi additive,

If you don't have too many miles I would not worry about the rear end, yet. Just check it to make sure it's full!!!
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Old 08-31-2017, 11:10 AM   #5
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Re: 2015 Silverado LTZ

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Originally Posted by Dad's72 View Post
Crazy. Seems counterintuitive but that is why I asked. How about switching to synthetic in the motor and rear end? Any input from any of you guys? I plan on changing my oil this weekend and have been thinking about it. Which synthetic oil would y'all recommend?
Actually, even older SBC's will perform a bit better with a bit of heat in them. Keeping an engine too cool will cause condensation in the engine, which builds sludge, which can choke an engine.

Gary
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My 1972 GMC 1500 Super Custom (Creeping Death) "long term" build thread.

The Rebuild of Creeping Death after the wreck

Quote:
Originally Posted by LONGHAIR View Post
I would never rebuild a 305.
Quote:
Originally Posted by prostreetC-10 View Post
I love using vacuum gauges as part of the carb tuning process. I hook the gauge to the inside of my garbage can and leave it there.
Quote:
Originally Posted by Marv D View Post
Remember Murphys 2nd law of mechanical relationships... "OPPOSING COMPONENTS ATTEMPTING TO OCCUPY THE SAME SPACE, AT THE SAME TIME, GENERALLY END UP OCCUPYING ADJOINING SPACE AT THE BOTTOM OF THE OIL PAN"
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Old 08-31-2017, 11:50 AM   #6
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Re: 2015 Silverado LTZ

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How many miles???
Any of the name brand synthetics are fine to use. Even the house brand at Wal Mart, HoReilly's and NAPA are usually bottles by Ashland, the company that makes Valvoline. Use a NAPA or Wix filter.

You need to find out if the rear end is a posi, if so, do NOT use synthetic it it. If it is a posi use a name brand 80w90 in it with the GM posi additive,

If you don't have too many miles I would not worry about the rear end, yet. Just check it to make sure it's full!!!
Thanks for the advice. I will jack up the rear end and see if it is posi or limited slip before doing anything. I think I will make the switch to synthetic. I want to research to see the benefits of making the switch to synthetic oil in the motor.
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Old 08-31-2017, 11:51 AM   #7
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Re: 2015 Silverado LTZ

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Originally Posted by GASoline71 View Post
Actually, even older SBC's will perform a bit better with a bit of heat in them. Keeping an engine too cool will cause condensation in the engine, which builds sludge, which can choke an engine.

Gary
Good to know. I will get the 200 degree thermostat when I put together the motor for my 72.
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Old 08-31-2017, 01:09 PM   #8
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Re: 2015 Silverado LTZ

That truck should have been running a Dexos 0w20 oil from the start...all 0w20's are full synthetic. If you run conventional oil and you have an engine issue they will NOT warranty it. It's 8qts, about a $90 retail oil change.
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Old 08-31-2017, 01:26 PM   #9
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Re: 2015 Silverado LTZ

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That truck should have been running a Dexos 0w20 oil from the start...all 0w20's are full synthetic. If you run conventional oil and you have an engine issue they will NOT warranty it. It's 8qts, about a $90 retail oil change.
Sho you right! I looked it up and found it out. Good to know. This is my first "new" vehicle. Getting used to all the new technology in the thing.
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Old 08-31-2017, 01:29 PM   #10
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Re: 2015 Silverado LTZ

I do have a question for y'all since this site always seems to have good advice. Not always but sometimes at red lights I notice that he idle is a little rough. And by rough it is pretty dang light really. It is only noticeable in the steering wheel and pedal. If I let go of the wheel it is barely noticeable. What could this be? I thought it might be cheap gas so I filled up with premium before heading to the coast and burned through it. Filled up and did it again. I got 22 mpg on those tanks so it ran fine. Just the idle.
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Old 08-31-2017, 04:44 PM   #11
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Re: 2015 Silverado LTZ

Any of y'all have this model truck and installed the leveling kit for the front end to be raised by 2"? I am thinking about leveling the front end and installing bigger tires. These tires just seem a little small for the truck. Last truck I owned was a 94 single cab Chevy which I leveled and put 31X10.50's on. I liked the look and would like to do something similar to this one.
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Old 08-31-2017, 09:57 PM   #12
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Re: 2015 Silverado LTZ

Quote:
Originally Posted by Dad's72 View Post
I do have a question for y'all since this site always seems to have good advice. Not always but sometimes at red lights I notice that he idle is a little rough. And by rough it is pretty dang light really. It is only noticeable in the steering wheel and pedal. If I let go of the wheel it is barely noticeable. What could this be? I thought it might be cheap gas so I filled up with premium before heading to the coast and burned through it. Filled up and did it again. I got 22 mpg on those tanks so it ran fine. Just the idle.
The direct injected engines have a tendency to build carbon on top of the valves, could be the cause of a rough idle. Whether it actually is or not, it cannot hurt to do a "top engine clean" or "fuel induction service" regularly. If you have somebody with the right equipment they can monitor any misfires, it may be slight but not enough to set a code.

Quote:
Originally Posted by Dad's72 View Post
Any of y'all have this model truck and installed the leveling kit for the front end to be raised by 2"? I am thinking about leveling the front end and installing bigger tires. These tires just seem a little small for the truck. Last truck I owned was a 94 single cab Chevy which I leveled and put 31X10.50's on. I liked the look and would like to do something similar to this one.
Have done several 2" level kits on these. Seems like they need another 1" in the rear unless you go with 1.5" front. I have also removed three due to popping in the front steering rack caused by excess inner tie rod angle. 285's fit nice on them.

By the way, NICE TRUCK!
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Old 08-31-2017, 10:55 PM   #13
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Re: 2015 Silverado LTZ

Thanks. Not bad for an almost 3 year old truck. It is I ridiculously great shape. I just got 40K miles. It came with the running boards, bed cover, and magnaflow duel exhaust. I will probably start by parking it on level ground and measuring to see what the difference is between the front and rear. I heard the rough country kit works well on these trucks.
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Old 09-01-2017, 09:43 AM   #14
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Re: 2015 Silverado LTZ

Quote:
Originally Posted by Dad's72 View Post
Good to know. I will get the 200 degree thermostat when I put together the motor for my 72.
For a SBC, I don't know if I'd go 20 degrees hotter than stock on a 1972. Should be a 180. But I've seen cats use a 185 and a 190 and not have problems. Being that you live in TX, you might wanna stick with a 180 in that application. There are lots of variables depending on your engine configuration. My comment was more geared towards the 180 to 185 T-stats. Because a lot of cats will toss in a 160 and then wonder why their engines are full of sludge and white goop.

Gary
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My 1972 GMC 1500 Super Custom (Creeping Death) "long term" build thread.

The Rebuild of Creeping Death after the wreck

Quote:
Originally Posted by LONGHAIR View Post
I would never rebuild a 305.
Quote:
Originally Posted by prostreetC-10 View Post
I love using vacuum gauges as part of the carb tuning process. I hook the gauge to the inside of my garbage can and leave it there.
Quote:
Originally Posted by Marv D View Post
Remember Murphys 2nd law of mechanical relationships... "OPPOSING COMPONENTS ATTEMPTING TO OCCUPY THE SAME SPACE, AT THE SAME TIME, GENERALLY END UP OCCUPYING ADJOINING SPACE AT THE BOTTOM OF THE OIL PAN"
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Old 10-05-2017, 02:21 PM   #15
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Re: 2015 Silverado LTZ

One more question for y'all. What should my batter gage be reading while idling and accelerating? I noticed a vibration sometimes and when I feel it I look at the gage and it seems like the battery is a little low. The two pics are while idling and while accelerating while the AC is OFF windows down.
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Old 10-07-2017, 11:14 AM   #16
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Re: 2015 Silverado LTZ

That is normal if you dont have alot of loads on computer comands the alterantor to a lower charge setting to be less drag on the engine
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Old 10-07-2017, 11:34 PM   #17
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Re: 2015 Silverado LTZ

Thanks. This is the newest truck I've had since my 94 1500. All these luxuries in my new one throw me for a loop sometimes.
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