bought a Pontiac G8 GT and age-old oil question

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cprince

Senior member
May 8, 2007
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Bought this used 2009 Pontiac G8 GT with 9k miles on it for $25k. I love the car--especially the 6.0-liter V8 engine. I know that the engine in this car is the same as the one GM use as the base engine of the Silverado 2500HD and an option for the Silverado 1500. So my question is, should I put synthetic oil in it? I kinda want to put regular oil and change it more often--like 5k miles. What do you think?

To clarify: If I go with synthetic, then I'll change the oil less often--like at the suggested 10k miles. If I put regular oil, then I would change it at 5k miles.

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Bignate603

Bignate603

Lifer
Sep 5, 2000
13,897
1
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What does the manual say? Personally, I'd just go with a good oil that matches what the manual suggests.
 
thescreensavers

thescreensavers

Diamond Member
Aug 3, 2005
9,916
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Yea, I would go Synthetic imo. But people will say its not worth it blah blah.

But according to UOA, it definitely is better for my car.
 
Kadarin

Kadarin

Lifer
Nov 23, 2001
44,296
16
81
I used to own a 2005 GTO with the 6 liter LS2 engine, and it came from the factory with Mobil 1. My advice would be to use whatever the manual states, but I am partial to synthetic oils.
 
Throckmorton

Throckmorton

Lifer
Aug 23, 2007
16,829
3
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Use synthetic. It's a fact that synthetic oil lubricates better and lasts longer. All things considered it's not very expensive to switch to synthetic and still change oil at 5k or whatever interval. Use a good filter too like Wix or Mobil 1.

Yes, some folks are saying that you should use what the manual says, etc etc. Well the manual doesn't give a damn how long your engine lasts, as long as it doesn't grenade during warranty. There is even a disincentive to carmakers to recommend synthetic, because a certain percentage of people will say "I'm not spending 0.1% more over the life of the car for synethetic oil, I'll just buy another car".
 
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Throckmorton

Throckmorton

Lifer
Aug 23, 2007
16,829
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http://forums.corvetteforum.com/c5-...t-about-synthetic-oil-in-the-c5-ls-motor.html

The C5 and C6 use synthetic because it's more better.

Here is a quote from Dave McLellan:

Corvettes have been using Mobil 1® 5W30 synthetic oil as the factory fill since 1992. According to Dave McLellan, the Corvette’s second chief engineer, “The most important reason was that the LT1 engine needed an oil cooler for certain high thermal stress situations. We were concerned that the external oil cooler plumbing, which ran near the exhaust manifold, was vulnerable to manifold heat. Tests with Mobil 1® showed that the engine ran cool enough that an external oil cooler was not even needed.” McLellan also added, “Corvette also used synthetics in Showroom Stock endurance racing for their power steering, manual transmission and axle.”
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LTC8K6

LTC8K6

Lifer
Mar 10, 2004
28,520
1,575
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There's no reason to use synthetic oil in that car other than "I want to".
 
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Vette73

Lifer
Jul 5, 2000
21,503
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Throckmorton said:
Use synthetic. It's a fact that synthetic oil lubricates better and lasts longer. All things considered it's not very expensive to switch to synthetic and still change oil at 5k or whatever interval. Use a good filter too like Wix or Mobil 1.

Yes, some folks are saying that you should use what the manual says, etc etc. Well the manual doesn't give a damn how long your engine lasts, as long as it doesn't grenade during warranty. There is even a disincentive to carmakers to recommend synthetic, because a certain percentage of people will say "I'm not spending 0.1% more over the life of the car for synethetic oil, I'll just buy another car".
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That would apply if he was going 10k+ on his oil. But since he said he wants to do 5k oil changes then he will not notice any real differance between a good regular oil and syn.

In all my years as an auto-tech and even shop owner I never had a engine fail or wear out sooner due to using syn or regular oil. Many have hundreds of thousands of miles on many cars with just basic upkeep. Failures were usually due to lack of basic upkeep.

Syn does offer some properties over a regular oil. But for a natural engine that is not being raced and changing the oil at 6k or less, for most the enigne will last just as long on either.

I use Syn in my CTS and Corvette but I also change them every 10k or once a year. My old truck gets regular oil and changed once a year or 5k. So far I have about 60k on the Corvette, 40k on the CTS, and over 160k on my Truck. I worked on a Pontiac Bonneville once with over 300k on it and it had regular oil and was changed around 5-6k each time.

For the OP I would use good filters (NOT Fram) and change every 5k with regular oil. But if you want to go farther on oil changes, tow/carry a LOT of weight, or track/race it then use a Syn.
 
E

Eli

Super Moderator | Elite Member
Oct 9, 1999
50,419
8
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It certainly isn't going to hurt anything, if that's what you're asking.

It might give you a slight(read: basically negligable) MPG increase, especially in winter.

It will enable you to go longer than 5k miles between changes without worry.

But as others have said, if you're religious with your 5k change regimen, it shouldn't make much of a difference.

That said, if you live in extremely hot or cold climates, it could do your engine good regardless of change interval.

Really want to know? Do oil analysis.
 
S

slashbinslashbash

Golden Member
Feb 29, 2004
1,945
8
81
You should have an oil life indicator built in to your car. It will beep at you and light up when it's calculated that the oil needs to be changed. In my experience, this happens anywhere between 7k-9k miles. IMO this is kind of a long time and synthetic would really be better.
 
V

Vette73

Lifer
Jul 5, 2000
21,503
9
0
crazySOB297 said:
Why not use synth and change at 5k miles or when oil analysis tells you to.
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Waste of money and time. Why not change your tires every 6 months, brakes pads, etc... It would offer a little more performance for tires and safety for brakes. But would not really change/offer that much better then using them as intended.

Same as running preimium gas in a car that it is not called for. Will not really hurt but will not offer any advantage.

There are some things worth doing extra. Using Syn in most cars and changing at 5k is not one of them.
 
O

onza

Diamond Member
Sep 21, 2000
8,937
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reviews.ragingazn.com
I just use regular oil in my 06 TL like the manual says. And I go in for oil changes when the computer in the car beeps at me which is 5500-7500miles depending on how I drive.
 
IcePickFreak

IcePickFreak

Platinum Member
Jul 12, 2007
2,428
9
81
You'll be fine with regular oil switching every 5k. If you hold in the left scroll wheel when turning on the ignition the DIC (Yes, Im serious) will display what's called Engineering Mode that shows a bunch of info you can't otherwise see on the standard DIC screens. One of those things is the Oil Life Monitor (OLM) and what percentage it estimates is left on the oil, granted that it was reset at the last oil change. Keep in mind too that the L76 6.0 in the GT holds 8.8qts of oil - ie. a friggen lot.

Oh BTW, it was determined that the G8 GT comes with regular dino oil from the factory, and the GXP comes with Mobil1. I personally use Mobil1 in my GT, but it's just what I always use.
 
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C

cprince

Senior member
May 8, 2007
963
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IcePickFreak said:
You'll be fine with regular oil switching every 5k. If you hold in the left scroll wheel when turning on the ignition the DIC (Yes, Im serious) will display what's called Engineering Mode that shows a bunch of info you can't otherwise see on the standard DIC screens. One of those things is the Oil Life Monitor (OLM) and what percentage it estimates is left on the oil, granted that it was reset at the last oil change. Keep in mind too that the L76 6.0 in the GT holds 8.8qts of oil - ie. a friggen lot.

Oh BTW, it was determined that the G8 GT comes with regular dino oil from the factory, and the GXP comes with Mobil1. I personally use Mobil1 in my GT, but it's just what I always use.
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Thanks for the info about the Engineering Mode. Do you know of any other tricks like this for the G8? I'm a car enthusiast wannabe.
 
MJinZ

MJinZ

Diamond Member
Nov 4, 2009
8,192
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0
Synthetic, if you actually drive your car as it is intended.

If you use Dyno on it, please just sell it and give it a better home.
 
thescreensavers

thescreensavers

Diamond Member
Aug 3, 2005
9,916
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Marlin1975 said:
That would apply if he was going 10k+ on his oil. But since he said he wants to do 5k oil changes then he will not notice any real differance between a good regular oil and syn.
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Well I am not sure if they used Good Regular oil, but the Oil that the dealer put in when I got the car showed some excessive wear in a UOA, When I switched to Synthetic UOA was extremely good. This was based on 3750 oil change interval. So yea you can defiantly tell a difference at 5k. And yea as long as you change the oil you should be good thats the most important part, but I like it that my engine is wearing less then if it was on Dino oil. And any how Why not? I can afford it and costs me 25 bucks for 5 quarts and quality filter of Castrol Syntec.
 
LTC8K6

LTC8K6

Lifer
Mar 10, 2004
28,520
1,575
126
There's still no reason whatsoever to use synthetic in that engine. And at 9 quarts a pop, it will be an unnecessarily expensive oil change with synthetic oil. Just use a good brand of regular oil and change it when you're supposed to and you will be fine.
 
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