Remember, this is not 1975, manufacturing and machining tolerances are much better than the "good old days". GM warranty's the engines in their vehicles for 100,000 miles breaking them in with synthetic oil. Oil consumption in the LS based engines, especially the aluminum block ones, is not usually ring to cylinder leakage, they have their set of issues.

From Mobils web site:
Myth: You should break in your engine with conventional oil, then switch to a synthetic oil like Mobil 1.
Reality:
You can start using Mobil 1 in new vehicles at any time, even in brand new vehicles. In fact, Mobil 1 is original equipment (it is installed at the factory) in:
Acura RDX

Aston Martin

All Bentley Vehicles

All Cadillac Vehicles

Chevrolet Corvette C6 and Z06

Chevrolet TrailBlazer SS

Chrysler 300C SRT-8

Cobalt SS S/C Coupe

Dodge Caliber dumdumdumdumdum, Charger SRT-8, and Magnum SRT-8

Jeep Cherokee SRT-8

Mercedes-Benz AMG Vehicles

Mercedes SLR

Mitsubishi Evolution

Pontiac Solstice GXP

All Porsche Vehicles

Saturn Ion Red Line and Saturn Sky Red Line

Viper SRT-10

One of the myths surrounding synthetic oils is that new engines require a break-in period with conventional oil. The fact is, current engine manufacturing technology does not require this break-in period. As indicated by the decisions of the engineers who design the high-performance cars listed above, Mobil 1 can be used starting the day you drive the car off the showroom floor.

 

Thanks Bird

 

I just did a h/c swap recently. I went with Castrol GTX conventional 10w-30. I plan on running that full time from here on.

 

From here on? Do you run the car hard or are you easy on it? Be careful because conventional cannot handle the higher heat/rpms like synthetic....therefore, it breaks down sooner than synthetic. If you go through with conventional, Id say at the least make your changes more frequent

 

I change the oil every 2k pretty much. It's a weekend car that's driven hard. I'm not real worried about it.

 

Sounds ok

 

What? 2K miles? Jesus christ. I change mine every 5K no matter what.

 

^^What oil do you use, just curious...

 

Yeah but he runs conventional and runs it hard. Smart to change more frequently on both counts

 

You can't hurt the motor changing it more often. And the conventional is 1/3 the cost of the synthetic stuff. I don't know. You will get 300 different answers on what oil people use and how often they change it.

 

I know that's what I was driving at

 

castrol gtx isnt a bad conventional oil but for cheaper you can have a better conventional oil... mobil clean 5000. Its almost as cheap as store brand oils but it even says performance oil on it. Its good stuff...It has lots of antiwear additives. Its been dry around here for royal purple... I had already been running the 5000 in my other vehicles and i liked it. So i threw it in my camaro and abused it a lil to see what it would do... it held up really well. better than castrol, valvoline, and penzoil... So for the price of store brand oil you get an oil that clowns on other conventional oils and is damn good... Im not saying im switching too it... just concider it over other conventional oils.

 

Yeah my one buddy runs Penzoil conventional. Him and his father have been using that in literally hundreds of race motors for several years. The motors have been tore down and the penzoil conventional was the best they have used. Practically no wear after "xx" runs or a season.

I have been using Castrol for over 10 years now. I just seem to like that oil over others. I'm sure there are facts that show oil X is better than oil Y for Reason Z.

 

Hmm...Im curious as to what problems would arise from switching to a good conventional oil for good...after 30k miles of synthetic. Would any harm be done? (seals, leaks, etc)

 

My motor has 90k miles on it. I am going to make a bold assumption and say that the previous owners ran synthetic oil since new. I do not think changing to conventional would be a problem. If anything, the seals would swell and stop any leaks since synthetic is thinner by nature. Now if you ran conventional all the time and switched to synthetic, that might pose a problem.

To each their own

 

Anyone else have a comment on this? I did a search but couldnt find a solid answer. After running synthetic since new for 30k miles, would any harm be done switching to conventional oil permanently?

 

179,000 + miles 3 cam swaps and 2 head swaps using Mobil 1 since it was new...the engine uses 1/2 quart of oil between oil changes every 5,000 miles and it see the red line every day..makes 452 RWHP...I prefer Mobil 1 but everybody has their own poison so to speak...

 

Royal Purple

 

I don't drive my GTO very often . I only change the oil once per year. I have driven less then 2K in the past 2 years. I Normally use Mobile One or Lucas products