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Synthetic oil: when to switch

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  • breakingcontact

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    I have one high mileage car (around 120k) and one "new" lower miles car (around 25k).

    Im kind of kicking myself for not running synthetic oil from the beginning in the new one.

    Im considering switching to synthetic in both of them but heres my hesitation. The one time i tried synthetic oil was in a real high mileage car (240k) and it started leaking bad. I switched back to regular oil and it stopped.

    When is it safe to make the switch to synthetic?

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    codygjohnson

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    Earlier the better. Synthetics tend to loosen up all the crud that's holding your engine together, hence the leaks. You'll also get a bunch of fresh crud floating around to plug up your oil galleries. It's a little more complicated than that explanation, but that's about what you risking running full synthetic in an older car.

    I've been told before 5000, before 20000 and before 30000 miles by 3 different mechanic friends. I don't trust either if them though...lol.

    Sage should be around at some point to give his prospective...I don't trust him either. Haha! I kid, I kid.
     

    TexCzech

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    Iv switched oil type in cars with all different level of miles , what iv learned at least with my experience is it will cause older cars with more miles to sometimes leak oil . Synthetic tends to be a little thinner especially when at operating temperature . Just remember once you make the switch you should not go back to conventional oil .
     

    rsayloriii

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    Switching back and forth won't harm it, but you won't get the benefits of the full synthetic. Switch it now and don't worry. I started my Tundra on synthetic around 100k or so. It's now at 208k. Only had to replace the valve cover gaskets recently due to a slight leak. But after 13 years and over 200k, I'd say their life was coming up. That's the only thing I've had to change on that engine other than normal scheduled maintenance. I run Mobile 1 and change it every 10k for the regular or 15k for the extended life. And before anybody gets in a tizzy over that, I've had oil analysis done by Blackstone Labs and everything is good to go. I'd highly recommend sending them a sample. Quite telling of how well everything is running. Also, use a good quality filter. IMO, stay away from Fram. Others will say they're fine, but I just don't trust them. I used to work in auto parts, and on long boring dead nights, I'd cut open the filters to see how they were constructed. From was by far the cheapest. Last recommendation would be to maybe change it once or twice at 5k after the switch, and then start doing longer. Get that analysis done and you'll know how far to push it without going too far.

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    diveRN

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    If the oil in your new car is relatively new, add some Seafoam and run it to the end of that oil's life. Change to synthetic and call it good.

    I've run synth in my 2k1 Silverado since I got it with 24,000 on it. No leaks. My wife's turbo charged 2.0L now has 31k on it and came with a synthetic blend from the factory, we switched to full synth at around 10k. No problems.
     

    vmax

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    synthetics aren't "thinner" than conventional oil and it does not hurt to switch back and forth

    Synthetics are produced from select base stocks and the molecules are arranged to be of the same size and shape this makes the oil have less resistance to flow, but not necessarily more "slippery"
    The viscosity index is the ability of the oil to maintain a constant flow characteristic over a wide range of temperatures, and this is another area where synthetics are way better than conventional mineral oil

    This is why you see synthetics used in cold weather environment and aircraft where you want the hydraulics to work the same at 50000 feet as they do at 10000 feet

    the only reason that switching to a synthetic would cause a leak is because you already had seepage around some gasket material in the first place and maybe just didn't know it yet

    what you need to buy is something like Mobil 1 High Mileage formula. It has gasket and seal conditioners in it that actually cause them to reverse the shrinking that they go though with age and reseal minor leakage
     

    breakingcontact

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    synthetics aren't "thinner" than conventional oil and it does not hurt to switch back and forth

    Synthetics are produced from select base stocks and the molecules are arranged to be of the same size and shape this makes the oil have less resistance to flow, but not necessarily more "slippery"
    The viscosity index is the ability of the oil to maintain a constant flow characteristic over a wide range of temperatures, and this is another area where synthetics are way better than conventional mineral oil

    This is why you see synthetics used in cold weather environment and aircraft where you want the hydraulics to work the same at 50000 feet as they do at 10000 feet

    the only reason that switching to a synthetic would cause a leak is because you already had seepage around some gasket material in the first place and maybe just didn't know it yet

    what you need to buy is something like Mobil 1 High Mileage formula. It has gasket and seal conditioners in it that actually cause them to reverse the shrinking that they go though with age and reseal minor leakage

    That makes sense. I did buy that specific oil but there were some small existing leaks im sure plus that engine was about done.

    So whats the verdict on switching with my two cars now? Suggested oils?

    -Without Life there can be no Liberty-
     

    Ranger60

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    I have a new truck and plan to switch at the 5000 mile oil change. Did this on my last truck with no problems. Have never switched on a high mileage vehicle, so, no input there,
     

    Charlie

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    If the oil in your new car is relatively new, add some Seafoam and run it to the end of that oil's life. Change to synthetic and call it good.

    I've run synth in my 2k1 Silverado since I got it with 24,000 on it. No leaks. My wife's turbo charged 2.0L now has 31k on it and came with a synthetic blend from the factory, we switched to full synth at around 10k. No problems.

    Seafoam is the very best stuff you can put in your gas tank and your crankcase.
     

    shortround

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    My 2013 Ford Focus came equipped with 5w30 synthetic motor oil blend and the "intelligent oil monitoring system." The manual instructed me not to change the oil until the "change oil" warning appeared on the "information center." When I hit 7,500 miles, I called Ford Customer Service and spoke with one of their "experts."

    He told me that the Ford oil was good for up to 10,500 miles.

    To hell with that! I changed my oil at 8,500 miles with full synthetic, despite the Ford recommendation.

    At cold start up, synthetic oil produces about 10 lbs higher engine oil pressure than the factory synthetic blend.

    It also takes a bit longer to reach operating temperature.

    No leaks or squeaks so far. I hope the drive train warranty is good for another 41,500 miles.
     

    vmax

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    My 2013 Ford Focus came equipped with 5w30 synthetic motor oil blend and the "intelligent oil monitoring system." The manual instructed me not to change the oil until the "change oil" warning appeared on the "information center." When I hit 7,500 miles, I called Ford Customer Service and spoke with one of their "experts."

    He told me that the Ford oil was good for up to 10,500 miles.

    To hell with that! I changed my oil at 8,500 miles with full synthetic, despite the Ford recommendation.

    At cold start up, synthetic oil produces about 10 lbs higher engine oil pressure than the factory synthetic blend.

    It also takes a bit longer to reach operating temperature.

    No leaks or squeaks so far. I hope the drive train warranty is good for another 41,500 miles.

    I run Mobil 1 in both my vehicles and I run them to 10K miles

    I sent used oil samples into the lab and had them tested at 5500 and at 8000 and the additive package, Viscosity and acid numbers were all great so I know I can go that far.

    Big rigs are running out to 30K plus miles now using oil analysis and higher quality oils



    I also run an extended performance filter and on my truck I re-grease every fitting at the oil changes and once in between, same with cleaning or changing the air filter.
     
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    M. Sage

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    synthetics aren't "thinner" than conventional oil and it does not hurt to switch back and forth

    Synthetics are produced from select base stocks and the molecules are arranged to be of the same size and shape this makes the oil have less resistance to flow, but not necessarily more "slippery"
    The viscosity index is the ability of the oil to maintain a constant flow characteristic over a wide range of temperatures, and this is another area where synthetics are way better than conventional mineral oil

    This is why you see synthetics used in cold weather environment and aircraft where you want the hydraulics to work the same at 50000 feet as they do at 10000 feet

    the only reason that switching to a synthetic would cause a leak is because you already had seepage around some gasket material in the first place and maybe just didn't know it yet

    what you need to buy is something like Mobil 1 High Mileage formula. It has gasket and seal conditioners in it that actually cause them to reverse the shrinking that they go though with age and reseal minor leakage

    This.

    The old "synthetics cause leaks" thing seems to go back to a time when synthetics weren't meant for daily drivers and didn't have the seal conditioners in them. Not the case these days.

    High mileage cars are gonna leak no matter what oil you put in them until you replace those worn/hardened/shrunken seals/gaskets.

    As for the mileage, I do 5,000 miles. Unless you drive a lot of freeway, 10,000 is simply too damn far. I've seen BMWs with plugged/collapsed filters at that mileage, and those get filled with 7 quarts of synthetic.
     

    breakingcontact

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    By "when to switch/change" i mean when can i make that initial switch over to synthetic not when should i change out the oil and replace.

    Thanks for the input. I tend to be a bit too old school but i know synthetic is better. Just need to make the leap with knowing i wont be doing any damage to the engines with 25k and 120k.

    -Without Life there can be no Liberty-
     

    AKM

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    unless youre going through mud or pulling loads everyday theres no reason you cant go 5000 on oil theres all sorts of crap on google to read
     

    rsayloriii

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    This.

    The old "synthetics cause leaks" thing seems to go back to a time when synthetics weren't meant for daily drivers and didn't have the seal conditioners in them. Not the case these days.

    High mileage cars are gonna leak no matter what oil you put in them until you replace those worn/hardened/shrunken seals/gaskets.

    As for the mileage, I do 5,000 miles. Unless you drive a lot of freeway, 10,000 is simply too damn far. I've seen BMWs with plugged/collapsed filters at that mileage, and those get filled with 7 quarts of synthetic.

    Can't speak for the BMWs, but 5k is a waste for synthetic. My truck gets 7 quarts of Mobil1. I've got the oil analysis to back up 10k on my engine. That's with a puralator filter.

    I highly recommend the oil analysis for getting the most out of the oil.

    Also, a filter change isn't going to hurt halfway through.

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    mroper

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    I run Amsoil in my Caddy STS it requires full Syn. If you are going to switch out the Oils to Synthetic it might not be a bad Idea to do a engine Flush on the 100K to get all the gunk out before you put the Synthetic in. The 20K I would just do the switch.
     

    txinvestigator

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    I purchased a VW Passat in September. It is a 2013 demo. It has synthetic, and changes are recommended at every 10k. In fact, VW covers the first three. My dealership offers a lifetime powertrain warranty as long as they service it.

    Just did the first one.
     

    Bozz10mm

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    I have one high mileage car (around 120k) and one "new" lower miles car (around 25k).

    Im kind of kicking myself for not running synthetic oil from the beginning in the new one.

    Im considering switching to synthetic in both of them but heres my hesitation. The one time i tried synthetic oil was in a real high mileage car (240k) and it started leaking bad. I switched back to regular oil and it stopped.

    When is it safe to make the switch to synthetic?

    -Without Life there can be no Liberty-

    You can change to synthetic any time. No harm will come to the engine.
     
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