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Discussion Starter · #1 ·
I know this issue has been discussed before, but not in depth. I have a csc powered L36 and I was considering switching to synthetic oil. I have heard numerous "testimonies" of leaks after switching to synthetic. Most of them say that it's due to the thinner viscossity of the synthetic. They also say that you shouldn't switch if you have a high mileage car. I only have 38,000 on mine. I don't know if it's a bunch of crap or what. Keep in mind though that none of these "testimonies" were from people with our engines. I would like some imput from anyone currently running synthetic oil.
Thanks
 

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I bought my car at 40K miles and waited till over 60K miles to start using Mobil 1. No more leaks now than what I had before.LOL
 

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i just started running it at 28,000 miles i didnt notice any difference but i have seen a lot of people that race their cars swear by it. They say it has saved a lot of their motors from being worse off when something goes wrong. Thats good enough for me. I am running royal purple
 

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i switched at 18k miles... my car was already leaking from the valve covers...

after a rocker install about 6k later i replaced those gaskets and now its been over 2 years and 72k miles and no leaks

i use mobil 1 supersyn 5w30
 

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Discussion Starter · #6 ·
Thanks guys. I think I will be switching over. Zoomer uses Mobile so I think thats what I will be going with.
 

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Just to add a little technical insight, there are some instances where leaks can develop after a switch to synthetic, but not for the reasons most people think. Synthetic is not slipperier than regular oil, nor is it any thinner. At operating temps, it's the same thickness and has very similar lubrication abilities as regular. The main advantages to synth are that it will flow at much lower temperatures (read: better protection on very cold starts) and it's much more resistant to thermal breakdown than regular oil. The fact that heat won't break it down as quickly gives the oil a longer service life and more consistent performance over that life.

Getting back to the leaks, all oils have ingredients designed to keep the seals flexible. When oil breaks down, it forms sludge and varnish. A coating of varnish over a seal will prevent those ingredients from getting to the seals, allowing them to turn hard and shrink. Synthetic oil won't varnish to the extent that regular oil will and will often clean away layers of old varnish that may be hiding an already existing leak. This is typically why some people see leaks after switching to synthetic. The reality is that the regular oil was just band-aiding a pre-existing problem.

So on a relatively young engine, you should have no problem. On an older engine, you're more prone to expose weak seals with synthetic oil, so there's some truth to the wisdom of not waiting too long to switch. I'd say, though, that anything under 100k miles would be pretty safe. If you do get leaks, though, the only REAL way to take care of them is to get the seal replaced, although some of the high mileage oils can help with this.

BTW, I've used Mobil 1 10w- and 5w-30 on my L36 since the first change at 1k miles. It's got 85k on it now and still purrs like a kitten, just as quiet and smooth as the day it left the factory. If you look under my valve covers, you'll see no varnish or sludge whatsoever and I have no oil leaks at all. My rate of oil usage is about 1 qt in 10k miles, which is very acceptable in my book. I swear by that stuff.
 

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i switched over to valvoline syn power at 165K in my gt, then mobil one at 200K, now mobil one in gt and gtp, switching now in the gtp, itll be first oil change since i bought it.

the only leak areas id be concerned about are the valve covers and oil pan gasket, but in my opinion it didnt get any worse than it was allready, and the added protection is worth it if it ever gets low. plus its good to change those gaskets anyway. :D

allways 10w 30

my .02
 

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I appreciate the thread you posted in regard to the synthetic oil "war". I do feel the same way and so i have chosen to blend 5w-30 mobil with a conventional.
 

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Amsoil Switchover

Four of the last six vehicles I've owned were switched over to Amsoil 10W-30 full Synthetic at over 100K. 1986 LeSabre Sequential Port 3800 ,sold at 220k still running great( needed 4dr for family). 1991 Park Ave Series 1 3800 sold at 265K still running great( needed minivan for bigger family) .1999 Montana 3400 still running at 160k and my 1998 GTP still running at 130K. All had 10k filter and 20K oil changes. None ever burned or leaked more than than 1/2 qt in 3K miles sometimes 1/2 qt in 5K. The Park Ave used Amsoils Bypass filter system and had not had the oil drained in the last 165K!!! that I owned it(after 12 New England winters the damn body had just had enough though)
 

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Mobil1 SuperSyth. is the shiznit
 

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I run either Castrol Syntec or Amsoil and have been sinc the car had about 8k miles on it, no leaks (now ar about 80k)
 

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i bought my GTP used with 26,000 miles on it and have been running amsoil 10W30 ever since and have had no leaks or problems with it.

one word of caution though- if you are going to switch to synthetic transmission fluid- DO NOT POWER FLUSH YOUR SYSTEM!!! just drain and replace the fluid and filter. I made the mistake of flushing mine and it stirred up a bunch of crap that ended up causing a nasty tranny slip. that resulted in me building a much stronger tranny with all the Intense parts though :D so dont flush the system unless you are looking for an excuse to beef up your tranny!
 

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Well, it seems a lot of others use Mobil 1. That is what I use as well. Switched over at around 70K. I replaced the valve cover gaskets (which were leaking before) when I did my rocker install....no leaks since. Very happy with using synthetic.
 
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