123k miles on 3.1L V-6. OK to switch to synth oil?

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1996 Beretta 3.1L V-6
123k miles
After reading all the glowing reviews of Mobil-1 synthetic oil in here, I decided to switch over from regular Pennzoil 5w-30 to
Mobil-1synthetic 5w-30. I just talked to my mechanic to schedule the oil change (too cold for me to do it), and he advised against it.
He stated that there would likely be leaks in seals, etc. after switching to synthetic, and that I would probably harm the engine if I switched to synthetic.
He advised to stick with what I've been using.
Is this correct, or is it something that only applied years ago, if ever at all?
The car's going in for the oil change next Tuesday so I need help here folks.
Many, many thanks to one and all for any help/thoughts/opinions.
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it all the time after all synthetic is just a super oil.I work for Freightliner.
Jim.J
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I'd say why chance it?
The car is only good for another 75K or so on the engine before it needs major work in any case(mostly sensors and valves and such), so I'd leave it as is.
Oh - change the timing gear/chain ASAP. Mine ate itself at 140K and if I'd done it at 80K I'd have saved myself $300 in extra parts.
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I'm getting along just fine on regular 10 w 30 oil ( 5 w 30 in the winter ). Month's ago some other mech posted advising against switching to synthetic oil on a high mileage car, something to do with the chemical reaction between the two oils & rubber seals which tended to shrink causing oil to leak.
========Harryface ======== 1991 Pontiac Bonneville LE, 3800 V6 _~_~_~_~276,100 miles_~_~_ ~_~_
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I've heard that synthetic oil has cleansers in it and that regular oil gets into some places and hardens or something to that effect. Then the cleanser takes the baked on oil and rips it off so oil can leak. I'm not sure which one is the right one. BTW has anyone heard anything about the oils for high mileage engines?
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If the engine has been well maintained and isn't burning or leaking oil now, I don't think it's likely to start with synthetic. Some heavily sludged engines might have problems because of the sludge being the only thing keeping seals from leaking..
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Robert Hancock Saskatoon, SK, Canada
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My understanding is that synthetics have "smaller" molecule size, which accounts for both their superior lube capability, and an increased tendency for leaks on marginal seals, etc.

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Synthetics "causing" oil leaks is a total myth, do your homework. Anyone who says it does probably doesn't realize that the leak in question was probably coming anyway. I changed my car from normal to synthetic a few years ago, I use Amsoil. Makes my bitter cold winter starts much easier as opposed to when I was running dino oil (read: the car usually would not start in the winter!).
Here was my sequence of events for my change. Valvoline max-life for 2-3 oil changes. Ran Amsoil engine flush to clean all the crap out before switching to synthetic (a step no doubt *many* do not do then bitch later) And I have been running Amsoil series 2000 0w-30 without incident ever since. Amsoil oil filters too, SDF-29 or SDF-34, I forget which one. Filter change every 6mo/12.5k miles, oil+filter change every year or 35k miles.
No oil leaks, no problems.
-GV
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The "synthetics causing leaks and damage" story is just a myth. The same was said of detergent oils when they first hit the market. If the vehicle's engine isn't sludged up, make the switch anytime you want to.
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Rich B wrote:

The original poster said he had Penziol in it so it probabaly is sludged up. I have seen two vehicles, my wife's first car and my parents 84 blazer which both had maintenance records from Fastlube who uses Penziol and both had what looked like fudge in the engine.
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wrote:

If not Pennzoil, what would you recommend dino wise? Or should I stick with the sludge maker since it's what I've been using?
Thanks!
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Rutger6559 wrote:

That is beyond my expertise and experinace, I haven't owned a lot of vehicles but used valvoline in my 88 and when I tore the engine down at 170,000 miles it still has the crosshash marks in cylinder walls but did have some crud built up on the pushrods. I switched my wife's Impala to mobile 1 at 16k when we bought it and my s-10 at 36k when we bought it. only other time I ever had an oil related problem was when I switched brands in my s-10 because the parts store was out of stock on valvoline so I bought the parts store brand. When I checked the oil next time there was white milky stuff in it. I had to drain and change it again. So in my experiance I learned to stay away from Pennziol, keep consistant in one brand even if they are supposed to all be able to be mixed, and don't chance your engine )and your life) to a Fram filter.
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wrote:

LOL!! On this point, we fully agree.
Thanks for the info!
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Pennzoil seems to have a past reputation for sludging up the engine, but I don't believe it's like that anymore - the API standards are much stricter than they used to be. In fact it's probably one of the better conventional oils for preventing sludge buildup these days..
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wrote:
OK, thanks for all the info guys. I'll stick with regular oil then and not chance anything, and I'll definitely get that timing belt/chain swapped ASAP as well.
So when is the use of synthetic appropriate? Is the ideal situation to only switch to synthetic on a brand new vehicle right when you get it home? Or is that even out of the question since regular oil has already been placed in the engine? Sorry for this, but I'm a bit confused on this now.
Many thanks again!!

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@yahoo.com says...

New cars usually come with synthetic. The only draw back to that is it takes a long while for the engine to fully break in. If you want to make a switch to syn oil try to do it before 80k is put on the engine. In an ideal world you would go 500 miles then 2500 miles and then 3000 miles on conventional oil then switch to synthetic. I started using synthetic in one of my cars that had 113k miles on it but it always leaked a little. After 4k miles it would be down a 1/4 of a quart.
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Really? I only thought it was new performance cars (Corvette, etc.) that came from the factory with synthetic. Then again, they don't list what type oil the car has been loaded with, do they?

Sounds like a good plan. Many thanks!

OK, switching to synth is definitely out for me then. Seems too risky.
Thanks again!!
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I bought two used cars, a 91 LeSabre 3.8L w/ 60K and an 00 Grand Prix 3.8L w/ 40K mi. Switched them both to Mobil1 and then they both leaked from around the oil pan. No other probs after getting the leaks fixed but it was at least $500 for each (and for those with 3.8's there is a GM TSB on a revised oil pan gasket install procedure).

the
I
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If the engine is reasonably clean, synthetic will be fine, a sludged up engine will react to synthetic's powerful detergents, and could leak at seals.
I went to synthetic 500 miles after the rebuild. Ran fresh engine for 20 minutes, changed oil and filter. Ran engine 200 miles, changed oil and filter. 300 miles later, switched to synthetic. The early change outs got rid of any metal shavings / solvents/ assembly lubes.
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M
Why did it cost $500 to replace an oil pan gasket on a 91 Le Sabre? That's about a ten minute job & a $12 pan gasket.
========Harryface ======== 1991 Pontiac Bonneville LE, 3800 V6 _~_~_~_~276,100 miles_~_~_ ~_~_
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