Changing to synthetic oil

[DreamsofaCobra]

Hey all,

I have a question about synthetic oils. I have a '68 Mustang with a rebuilt 289, with several thousand miles on it since the rebuild. I want do the best for the car, so I was thinking about going from Castrol GTX (the oil I have been using,) to Mobil 1 or other synthetic. Going to the auto parts store I trust the most, I have heard (on two different occasions):

A: sythetic is always better, always...

and

B: Don't bother unless you have a new car. If the car is broken in on standard oil, it will not like changing to synthetic.

I have reason not to believe B, knowing you should not break in a car on synthetic at all. I was wondering if there was anything to what she was saying though. Will my precious car not like me if I make the move to synthetic? I don't mind the higher cost, and the engine has been modded, (cam, headers, induction, etc.)
What do you all think?

[Steel]

generally, its ok to put in synthetic after a car has been broken in with synth. Usually on OLDER engines, like high mileage, synthetic is bad because it can squeeze by gaskets that the dino oil couldn't.

[DreamsofaCobra]

ahh, now that makes sense, but what about a rebuilt engine?

[Neutrino]

Originally posted by DreamsofaCobra
ahh, now that makes sense, but what about a rebuilt engine?

well i presume you have a new gasket so you should be ok with syntetic.


imo it is always better to use syntetic its properties are so much better that dead-dino stuff-especially if you push hard the engine.

[SaabJohan]

There are many myths about syntetic oil.

1. Synthetic oil and conventional oil use the same cleaning addetives so synthetic can't cause old dirt to loose and damage the engine.

2. Synthetic doesn't attack seals, if they are fresh it's going to be OK.

3. Synthetics doesn't in general have lower viscousity than conventional oils, but they are less sensitive of temperature changes. This means that if you have two oils, one synthetic and one conventional with the same viscousity at 100 degrees C, the synthetic will have lower viscousity at 0 degrees C compared with the conventional oil. Some people seem however to think that the synthetic oil is too thin when they see it, pouring it into the engine.

4. Synthetics have lower friction, therefore they aren't always suited for break in. Aeroengine manufacturers (as one example) therefore use a special break in oil which is also synthetic but it contains particles to increase wear.

5. Synthetics doesn't make the oilpressure to drop, some pressure gauges have however problems to show a correct value with synthetic oil (the value drops).

[Holyterror]

Here's the low-down on "bad things" that can be attributed to synthetic oil:
[list=1]
[*]Leaking
If your seals are bad, leaks are a definite possibility. You see, synthetic oils are more slick than conventional oils. In my experience, almost all synthetics have greater surface tension as well. These two traits combined mean that synthetic oils find it much easier to slip through bad seals. If you engine already leaks, then switching to synthetic will only make it worse. Of course, the oil is not actually creating a problem, but making it more obvious. In this way, it's almost a sort of diagnostic tool, albeit an expensive one. Bottom line: if you know there's a problem, fix the engine before you switch.

[*]Mysterious noises
You bought synthetic oil for reduced friction, right? Well, guess what? Some of that friction was probably dampening NVH (noise, vibration, and harmonics) in your engine. For example, a slightly improperly tensioned timing chain that was silent before now makes a little noise. Again, the oil did not create a problem, but made it apparent. This is one of the first things you will probably notice after switching to a synthetic oil. Not really a downside, just an explanation of a sometimes misunderstood effect.

[*]Improper break-in (or no break-in at all)
Synthetic oil is bad for break-ins. It's simple: you need some friction transfer between the rings and the cylinder wall for them to seat properly. A really low-friction oil (such as Amsoil 0W-30) will probably never allow an engine to break-in. Here's what happens when you run synthetic on and engine that hasn't been broken in:

The synthetic oil doesn't allow the rings to seat, so there is not a good seal between piston and cylinder wall. The effect is that a lot of your expensive new oil ends up in the combustion chamber, and the stuff that remains in the crankcase ends up contaminated with all those lovely bi-products of combustion. You lose oil, and the oil loses its ability to perform. Bottom line: don't use synthetic for break-in.

I've heard some people say that they don't want conventional oil to ever touch their engine so it'll be completely clear of varnish and sludge deposits. Honestly, if you're good to the car through break-in (i.e., follow the manufacturers recommendations) and change to synthetic soon after, then you should be fine. My method is this: as soon as I can no longer detect any smoke (sight or smell) from the exhaust, I change the oil and drive it for another 200-300 miles. I then drain the oil and check it for any sign of combustion bi-products (indicating blow-by). You can send it to a lab if you want to be really sure. If the oil is clean, then I trust that the break-in has been successful, and I then go synthetic.

[*]Alienation from certain circles
And, finally, if this sort of thing matters to you, then be forewarned that using synthetic oil will probably alienate you from a number of people. All the Ford guys I know won't touch it (like I won't touch a Ford), and plenty of mechanics swear by the same dinosaur oil that their grandfathers used. It seems that here in the south, the myths are even more popular than elsewhere. Most V8 guys around here like their oil thick and sludgy. Some of them run 20W-50 in engines that could probably do 5W-30 most of the time.

Honestly, unless you tell them you're running synthetic, they'll probably never know. And if they wonder why your motor makes slightly more power than another, give them some bull about rod-to-stroke ratio or something. :smoker2:[/list=1]

All joking aside, there really aren't any disadvantages to running synthetic. And the advantages are endless: reduced wear, better exonomy, extended drain intervals, and on and on and on. As far as what brand, Mobil 1 is, in my opinion, the best stuff you can get off-the-shelf. The best oil you can buy, period, would have to be Amsoil. You're not too likely to find it at Autozone, but you can easily order it online at Amsoil.com. All of their oils are API certified, and most of them guaranteed to last 1-year or 25,000 miles, whichever comes first (providied that you use it in conjunction with their oil and air filters). Hard to beat that. I currently Amsoil 10W-30 in two of my vehicles, and the Series 2000 20W-50 is likely to end up in my hi-po Nissan motor.

Hope that helps!

[lapspec]

Holyterror has some good points, it does take longer to break in with a synthetic oil however filling from day one is ok. Corvettes, dodge viper, and other preformance vehicles come factory filled. If your looking for performance on your baby I would highly recommend the Amsoil 0w-30. I use it in everything!!! You can learn more about Amsoil at www.synthetic-lubricants.com there is even a comparrison between Mobil 1 and Amsoil There..

[Neutrino]

Originally posted by lapspec
Holyterror has some good points, it does take longer to break in with a synthetic oil however filling from day one is ok. Corvettes, dodge viper, and other preformance vehicles come factory filled. If your looking for performance on your baby I would highly recommend the Amsoil 0w-30. I use it in everything!!! You can learn more about Amsoil at www.synthetic-lubricants.com there is even a comparrison between Mobil 1 and Amsoil There..

i just love how unbiased that site is......



i'm sorry but i need uninterested third party tests to believe them

[lapspec]

I was an unbeliever too. But if you notice on that site my 40,804 miles without an oil change is more prove than what you may be able to come up with with the brands you use. Proof is in the results. Bias as to other oils Yes because I found the best!!!

If you wish to see the results click on the 40804 link on top of the page. These are the actual reports all 3megs of them

[NSX-R-SSJ20K]

you sound like a commercial for oxy clean

sorry

[Neutrino]

Originally posted by lapspec
I was an unbeliever too. But if you notice on that site my 40,804 miles without an oil change is more prove than what you may be able to come up with with the brands you use. Proof is in the results. Bias as to other oils Yes because I found the best!!!

If you wish to see the results click on the 40804 link on top of the page. These are the actual reports all 3megs of them

so you would have us belive that you actually pushed your car 40k with only one oil change...there is only one reason you would do that...if you work for them....nobody in their right mind would do that to their car unless you stood something to gain....so I'm sorry but that makes your views biased

[lapspec]

Does it work? If it does dont knock it. I became a dealer because it does work. Call it biased or whatever. It works and it makes me money. I get the best of both worlds. One person who is a Amsoil dealer uses the slogan "Change your mind not your oil" If you refuse to accept facts that is up to you, there are thousands of believers in Amsoil many right here in the forum. You are entitled to your opinion that is what the forum is all about. Ah freedom of speech. How nice it is!!!

[lapspec]

PS You can be happy that Amsoil has stood by synthetics from the beginning Expert agree that is why synthetic oil is available. Amsoil came first than mobil one. Mobile one started out at 25,000 mile change intervals but they caved in now they say do it according to the manufactures recommendations. No other oil company has stood by there product. Lubricantion Experts agree....