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I have a 2.4L 2004 Santa Fe (3 of them actually). I recently changed to Mobil 1 full synthetic oil 5W30 about 17,000km ago. I'm using a genuine Hyunai Oil Filter. I made this change at approx. 205,000km after it using Castrol GTX dino oil since Day 1. Some have told me it's not good to swtich to synthetic with this many km's on it, other's have balked at that saying synthetic is always better. (I'd appreciate your thoughts on this issue as well)

For the first 10,000km all was fine, albeit it was warmer weather last Fall.

Did the first change at 10,000km and by 6,000km into the second oil change I noticed rought start-up in the morning in weather that was just below freezing (around 0 to -5 degrees C).

When I say "roough start-up" I mean the motor just "sounds" rough. It's not misfiring or anything, just doesn not sound "smooth". I thought I heard some slight engine pinging on the intial few seconds sometimes. Then it just runs "loud" and noisy. I guess the best way to describe it is it doesn't purr like the kitten it used to. Once it fully warms up it's fine, but even then it sounds a bit "hard".

So by 7,000km into my second oil change it was bothering me so much I decided to change the oil out and put in fresh Mobil 1 5W30 synthetic oil and a new genuine Hyundai filter. It ran very "smoothly" for the first 700 or so km. Now 1,000km into that last oil change it is again having these hard cold starts.

I thought perhaps it was an oil pump problem but my Hyundai dealership assures me it's not an oil pump problem and I've left my vehicle with them overnight and although they agree it sounds rough on start up, they can't find anything wrong with it persay.

This morning is seemed a bit better (at 7 degrees now), but still "loud".

They recommended I return to 10W30 conventional oil.

Before I do this I wanted some thoughts or experiences from others who may have a similar vehicle and switched to synthetic oil with the Hyundai filter?

I really would like to keep using Mobil 1 synthetic, but I can't help but think it is somehow associated with these hard morning starts and a "loud" sounding motor. During my last oil change there were some very small flecks in the bottom of the used oil pan about the size of a grain of sand...maybe 30 or so. Of course I'm wondering if the cold starts, metal on metal have caused this or if it's just my imagination.

I'm also wondering if I should try and use the corresponding Mobil 1 synthetic oil filter with this oil instead of the genuine Hyundai one? I know the Hyundai ones are very good, but I'm just thinking out loud.

I'm also wondering if perhaps I should be using Mobil 1 10W30 oil instead of 5W30. I have previously done a lot of research on bobistheoilguy and everything I've read suggests the lower first number is better in all vehicles for start up lubrication (ie 5W30 over 10W30 and even some suggesting 0W30 is even better, although I haven't tried that).

And then there's the issue of returning back to dino oil. Again, some say this is not good to do once you've had synthetic in it, others balk at that as well.

Any help, and especially any similar real life experiences around this issue would be most appreciated.

Thanks!
 

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If you changed viscosity, then yes, the symptoms you're noting might be due to the change. But if you just changed from the same viscosity of conventional to synthetic, I doubt it.

BTW, the narrower the viscosity range, the more shear stable the oil tends to be. Everything else being equal, a 10W-30 is more likely to maintain its original viscosity in long service than a 5W-30. But the 5W-30 will have less initial engine wear on cold starts. Everything is a tradeoff. But this may be the reason you're noting a change in how the engine runs with time in service.

When you start getting up to extraordinaryly high mileages, I'm a believer that you don't rock the boat - just keep doing what you've been doing because it is working fine. If I had a 205K km car using conventional, I would have stuck with conventional.

- Mark
 

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Sounds to me like you should have stuck with dino. Have you had the valve cover off? I would have investigated the relative amount of oil gunk in the motor before I shocked it with synthetic because the gunk loosens up when you do that. My guess is you loosened some gunk and it probably clogged the little tiny oil ports in the lifters. That would give you valve chatter, and eventually it would smoke.
 

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Sounds to me like you should have stuck with dino. Have you had the valve cover off? I would have investigated the relative amount of oil gunk in the motor before I shocked it with synthetic because the gunk loosens up when you do that. My guess is you loosened some gunk and it probably clogged the little tiny oil ports in the lifters. That would give you valve chatter, and eventually it would smoke.
This. Likely over time your use of dino oil has built up deposits up around the cylinder heads, and the superior cleaning agents of synthetic are now loosening those up and potentially causing clogs in the ports or even the oil filter (which could explain your better results right after a change). It's not always a "bad" idea to switch to synthetic with higher mileage, but usually a motor flush is recommended before you do. This will help get that junk out so you can start fresh with the synthetic. You could still do an engine flush right before your next oil change and see if it helps. Something like this:
Gunk MF3 High Mileage Motor Flush - 32 fl. oz. : Amazon.com : Automotive
 

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Everything is debatable in an "oil thread", but I think the concerns about sludge and clogged oil passages are overblown. If the car has had a reasonable oil change schedule through its life (and putting 200K+ km on an engine without significant problems is an indicator it has), then I doubt sludge is an issue. Most of the time when this is a problem is because oil changes have been neglected. And the ability of synthetic to "loosen" sludge is not that much greater than conventional - both have similar detergent packages and the detergent is what loosens sludge, not the oil itself.

Also think that if clogged oil passages were an issue, the symptoms would be a lot more severe than a little extra noise at startup and after the oil has some time in service. The fact the engine runs more/less normally after warmup indicates to me that things are basically Okay.

I'm also not a fan of engine flushes, especially if the car has had regular oil changes. More harm than good.

Again, always lots of opinions in oil threads.

- Mark
 

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Mobil 1 synthetic is a good lubricating oil but it is loud. Good for sport car. Try a different brand of synthetic like Valvoline or Castrol. I find them a bit less noisy than Mobil 1. My Santy really likes Valvoline and it can runs like a 3 years old SUV. It is quite amazing. The idle speed is right on the specification 650 rmp. I did put in a front strut bar and the rear spring cushion though. Planning to change all sway bar end links to make it goes quieter.
 

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Duh... thread is three months old with no feedback from OP...?
 
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