Synthetic oil
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From: Savannah, GA
Synthetic oil
I'm wanting to run synthetic oil in my 300, but I know the gaskets were made to expand with petroleum based oil. So if I put synthetic in is it going to leak? If so, which gaskets would I need to replace?
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Joined: May 2006
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When I bought my 88f150 300cid it had 101,000 miles and I ran Mobil 1 in it for three years until I sold it to my brother in law, with no problems, no leaks, it did not burn any oil. I use Mobil 1 in all my vehicles and my kids cars. No problems what so ever. Ive used it my wife 2005 Nissian Altima since it was new, I used it my kids 2002 Chevy Malibu since it was new, I use it my kids explorer with a 4.0 sohc V6, bought it with 88,000 miles on it and it now has 110,000 none of them ever had a problem with leaks or using oil. The rumors that surround Synthetics are all bulls**t. A lot of the hot rodders run synthetics like Amsoil and Royal Purple in cars that they have invested big bucks because synthetics are just that much better than regular oil.
Originally Posted by N7ghtwolf
I'm wanting to run synthetic oil in my 300, but I know the gaskets were made to expand with petroleum based oil. So if I put synthetic in is it going to leak? If so, which gaskets would I need to replace?
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Joined: Jun 2003
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Synthetic oils CAN cause leaks that never existed before. Been there, done that......more than once. The reasons are simple. Synthetic oils typically have less viscosity and much greater lubricity (slipperyness) and cohesion (ability to follow) than coventional oils. They can sometimes seep past gaskets that would not otherwise leak with coventional oils. The only way to find out if your gaskets will leak is to try it. Odds are in your favor. If it does start to leak you can always go back to conventional oil. The leaks should stop. Always have for me. Let us know what happens. Cheers.
Postmaster
Joined: May 2004
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I use synthetic in my new vehicle...no problems at 100K. But the question was about using it in old vehicles, and leaks forming isn't BULL****.
I opted to stay with regular oil on my 83 with 170K. Why not? It treats me good, I don't drive it alot. The last thing I need is a bunch of new leaks.
I opted to stay with regular oil on my 83 with 170K. Why not? It treats me good, I don't drive it alot. The last thing I need is a bunch of new leaks.
5th Wheeling
Joined: May 2006
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From: s.e.iowa
Ive put synthetic oil in over 100 cars with 80,000 and more miles and have never seen any leaking problems as a result. the synthetic oils have to meet the same standards that might affect seals and gaskets as petroleum oils. Oils are rated for their viscosity at 100 degrees celsius. If it is a 30 weight oil both synthetic and petroleum will have the (very close to the) same viscosity at 100 degrees. But petro and syn oil have very different viscosity at other temperatures. If you look at a curve of viscosity vs temperature petro oils get thicker much faster than syn oil as the temp decreases and the petro oils lose their viscosity ( become thinner) as the temp goes higher than 100 degrees.
Postmaster
Joined: May 2002
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From: Broken Arrow, OK
We run synthetic (Amsoil) in both of our toys, but not in the daily drivers. Oddly enough, this is for economic reasons. The toys get Amsoil because they don't get driven a lot. I would need to change petroleum oil every three months whether I drive them or not. With synthetic I just do it every year and it saves me some money. Synthetic also is better for the engine. On the daily driver I run petroleum oil because it isn't worth the money. After 298k miles on TropArtic I don't see any reason to change. It would double my oil cost for added protection that my 300 doesn't need. When I finally get around to a new engine, I'll run synthetics. I've had bad luck changing formulas that work, so I won't change anything for now.
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Post Fiend
Joined: Mar 2002
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From: Bonita Springs FL
The benefits from using synthetic oils are clear. I don't think (?) anyone is really disputing that.
As for whether or not they may cause leaks, it depends. I switched my '89 to synthetic about 10k ago. It had 140k on the clock. The valve cover gasket leaked before, and it wasn't any worse after I switched it. I changed the gasket and it hasn't leaked at all since.
As for whether or not they may cause leaks, it depends. I switched my '89 to synthetic about 10k ago. It had 140k on the clock. The valve cover gasket leaked before, and it wasn't any worse after I switched it. I changed the gasket and it hasn't leaked at all since.
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Joined: Sep 2005
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From: Clermont county, Ohio
I haven't used synthetic in mine, but a close friends 300 started leaking after switching to synthetic. Switched back to petro. and the leak stopped. My thought is this, if you have a new or very low mile engine, go ahead and switch, if you have a high miler stick with what has been working.
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Joined: Jun 2003
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If your vehicle is a keeper, regardless of mileage, you can try the synthetic oil. Some will leak, most should not. If it does leak you can always switch back. My experience has been, numerous times, that the leaks will stop. Degrease the engine before the oil swap so the origin of the leak is obvious.
If it's simply a valve cover leak and nothing else, it's worth replacing just the one gasket and continuing to run the synthetic. I personally drive too much to stop and change my oil every 3,000 miles. Time is money. Synthecic oil is money well spent.
If it's simply a valve cover leak and nothing else, it's worth replacing just the one gasket and continuing to run the synthetic. I personally drive too much to stop and change my oil every 3,000 miles. Time is money. Synthecic oil is money well spent.
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Joined: Jul 2003
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From: Nashville
After my 300's new cam is broken in I'm switching it over to synthetic. Wouldn't bother before as the motor was leaking like a sieve. Now with all new seals/ gaskets I certainly don't mind, and the price difference between regular and synthetic oils isn't really that much any more.
Used Mobile 1 in another vehicle and it ran for over 250K with the oil only ever getting changed every 20K- 25k miles. Dropped the oil pan for a gasket change at 125K miles and it was clean as a whistle. Little varnish from blowby but ZERO sludge. Previous engine in the car died at 140K after the oil pump failed from the screen getting clogged... and it had religious 5k mile oil changes it's whole life. When I started tearing down my 300 with only 75k on it I was horrified at the amount of gunk in it.
Used Mobile 1 in another vehicle and it ran for over 250K with the oil only ever getting changed every 20K- 25k miles. Dropped the oil pan for a gasket change at 125K miles and it was clean as a whistle. Little varnish from blowby but ZERO sludge. Previous engine in the car died at 140K after the oil pump failed from the screen getting clogged... and it had religious 5k mile oil changes it's whole life. When I started tearing down my 300 with only 75k on it I was horrified at the amount of gunk in it.
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Joined: Apr 2006
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From: Savannah, GA
Is it safe to degrease the engine with a power washer? Or do I need to use a little elbow grease and buy a lot of engine decreaser and brake cleaner? As for the valve cover gasket, i'll probably end up replacing it anyway since they're cheap and i'm taking the valve cover off to re-paint it. As for the oil pan, how tough are they to get off from under the truck?
Also, what viscosity should I use? The normal 10w-30 that i'm running now?
Also, what viscosity should I use? The normal 10w-30 that i'm running now?
Last edited by N7ghtwolf; May 23, 2006 at 02:35 PM.
Mountain Pass
Joined: Feb 2005
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not true, its a bear, but it can be done with the motor where it sits, take all the pan bolts off, and drop the pan the 3 to 4 inches that it drops, and then work the gasket down and under ther oil pump pickup, it can be done, Ive done it before, no leaks... 15K on it so far...