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Is it safe to change to Synthetic?


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I Drive a 2000 Sierra that has a 4.8L Vortec in it The engine has 128,000 miles or so on it now. I drive a fair amount, almost 3,000 miles every month or so going back and forth to School and upstate New York. That being said, conventional oil doesn't stay as clean as I'd like it to and I find myself changing it almost every month and the money adds up. I'm wondering if it's safe to change it over to Synthetic oil (Without it leaking) and whats the best way to go about it? If I can get away with changing the oil less often by using Synthetic, would be great. I do oil changes from 3,000 to 3,500 miles, but I don't know what the previous owner maintained, because when I got it, It was a bit of a mess. So i have no idea the conditions of the oil seals. I'd appreciate any feedback I can get!

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I have issues here. But there again, I have many issues..

 

I am not so sure I would go to a full synthetic with the miles and not knowing what the previous owner has ran in it. Your motor will not be harmed internally with changing over. The viscosities are the same but the molecular structures are different.. You may or may not start leaking after running full synthetic but if you do, you always will afterwards.... Just because your oil is getting dirty, does not mean that you have to change it at 3000 miles. The same will go with synthetic. Just because you should be able to make it to 6000 miles prior to changing, does not mean it will not be dirty at 3000 miles. Air filter quality, oil filter quality, quality of conventional oil, etc etc.. will all play into this as well. What are you running now for all of these?

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I switched my 95 blazer to mobil1 high mileage 10W40 at 122k miles this year and it's running a lot better than it used to on conventional. I changed my 1990 miata from conventional to high mileage mobil1 5w30 because it had a horrible ticking sound at over 120k about 4 years ago and it's still running better than ever at 155k. I also changed my 07(GMT900) 5.3 to mobil1 at around 90k (i got it used at 87k in Feb 2012) and it made the thing sound a lot quiter... Didn't do much for the AFM consumption but I havent noticed any new leaks. I did the same thing to my stepdads 02 tahoe (5.3L) with well over 100k and it ran fine too.

 

I wouldn't say it looks any cleaner though than the conventional did... The oil still comes out dark at 5k oil changes.

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I have a K&N Filter for both Air and Oil Filters, and last time I used Castrol Conventional Oil. My main worry is the leaks, because like you said, I don't know what the previous owner was using.

I would dump the K&N filter and put the OEM air filter back in.

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I switched to synthetic at 100k. I used conventional Castrol since new, changing at 5000k intervals. I now use Castrol Edge and change by the OLM, which prompts usually at 7-8k. I've noticed no adverse effects. Saves money, time & a reduction in the waste stream. I was a dummy for not starting this routine since purchase.

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I respectfully disagree with the above analogies, after that many miles, IF there is any sludge in the engine, the highly detergent synthetic oil will remove it, and you will start to have seal leaks.

 

JMHO

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Why not test a sample of your current oil at the next change and see what is recommended for change interval

With todays oils you could go 5k with no issues. Like stated by txab, take a sample of your current fill and send it off. You might be surprised by your driving conditions that you could go longer and still be protecting the engine. I have seen conventional oils go as far as 8k miles with no issues and the oil was doing its job. That would be my first step if you want to save some money. That way you can run inexpensive conventional and max out your mileage.

 

You can switch over to synthetic and get the benefits of it cleaning your engine along with longer drain intervals. Will it leak, possible, but over time the leak could also stop, since more than likely the synthetic cleaned up the sludge that was keeping the seal from leaking and once the oil was able to reach the seal, it could also allow the seal to swell like it is supposed to do and stop leaking. Mostly when the sludge gets cleaned out, the seal has shrunk due to not having any fresh oil contact it to swell. Then the sludge is removed and the seal starts to leak. But once it gets fresh oil on it and swells the leak will stop. Now a damaged seal is a different story. High mileage oils have extra conditioners in them to do just that, help seals swell so they do what they are intended to do.

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I respectfully disagree with the above analogies, after that many miles, IF there is any sludge in the engine, the highly detergent synthetic oil will remove it, and you will start to have seal leaks.

 

JMHO

sorry, but this is not true!!

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you can switch back and forth with no issues. many, many oil threads out there. most who are extra loving stick to the big boys, the mobil 1's , amsoil, castrol, etc. some are rated better than others, depending on where u read it. most guys nowadays, myself included like the full synthetic, but it is just an opinion. there must be a reason though why the corvette motors and a lot of the big (re:expensive/high end) cars have a full synthetic mobil 1 in them from the factory.

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you can switch back and forth with no issues. many, many oil threads out there. most who are extra loving stick to the big boys, the mobil 1's , amsoil, castrol, etc. some are rated better than others, depending on where u read it. most guys nowadays, myself included like the full synthetic, but it is just an opinion. there must be a reason though why the corvette motors and a lot of the big (re:expensive/high end) cars have a full synthetic mobil 1 in them from the factory.

Yes from the factory, not 128k later after using conventional oil.

 

JMHO

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