Oil change today... full flush or simple change?

[Kingsly]

I am taking my 93' BMW 325i (102k/mi) to the mechanic today for an oil flush and switch from dino to synthetic. I picked up 7 bottles of Mobil 1 10w-40 High mileage (its on 20w-30 dino now) thinking that the slight increase in thickness will negate any leakage that I have read synthetic causes when coming from dino.

My main question is: The mechanic wants to flush the system with this double bottle kit (one bottle goes into the old oil, idled for 10 min, and then the oil is replaced with synthetic and the second bottle is added to that). I am worried because as nice as it sounds to have the engine made all shiny and clean, I have also read about perfectly fine engines that have failed after having all the old buildup removed (I guess because it was acting like a sealant of sorts between all the worn parts)

Should I simply tell him to drain the old stuff and put in the Mobil 1? If I did this I would probably change it again (to BMW spec Mobil 1 0w-40) after 1k/mi as a kind of "mini flush".

Is there any danger of the Mobil 1 reacting adversely with what's left of the dino in there?

Help?

 

[robl]

From what I understand that is a myth about synthetics causing leaks. If it didn't leak before, it shouldn't leak now. Switching shouldn't make it leak. There is no 'danger' of the Mobil 1 and the old oil, oils are compatible, so no danger should be had. I'd probably just drain and fill. But that is just me. Do they want to charge lots for the flush, etc?

 

[Kingsly]

They are not charging a particularly large amount... I just don't like the idea of foreign chemicals being added to my engine without me knowing what they are. Furthermore, the engine is in fine shape and I don't think it even needs a full flush. Simply adding Mobil 1 and driving around for 1k/mi is enough of a flush for me.

 

[KW]

If it were mine I would just drain and fill with the Mobil 1. I would only run the M1 for a few thousand miles the first time. The flush might work to well and do more harm than good.

 

[Doc8404]

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From what I understand that is a myth about synthetics causing leaks. If it didn't leak before, it shouldn't leak now. Switching shouldn't make it leak.

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+1

 

[WishIhadatruck]

I wouldn't let anyone flush my engine with anything if I didn't know what it was. I switched a car to synthetic with over 95k miles on it once with no leaks as a result and it still doesn't leak enough to drip on the garage floor now with 203k miles on it. I just switched another car over with 101k miles on it to synthetic and 1500 miles later I don't have any leaks yet.

I'd skip the mystery flush. I did do 2 Auto-Rx cycles on the most recent car before switching since I did not know what the past history was on the car and wanted to try and clean it up if it needed it first. The first car I'd owned most of its life and knew it was probably clean inside due to frequent OCI's.

 

[Kingsly]

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If it were mine I would just drain and fill with the Mobil 1. I would only run the M1 for a few thousand miles the first time. The flush might work to well and do more harm than good.

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I am just going to drain and refill then. After a few thousand miles should I go to the BMW suggested 0w-40 or stick with the HM stuff?
Thanks.

 

[B00SS]

I would treat the switch to synthetic as I would any other oil change. Dump the old (dino), put in the new (synthetic)and run it a normal interval. Or maybe even longer.

 

[AndyH]

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I am taking my 93' BMW 325i (102k/mi) to the mechanic today for an oil flush and switch from dino to synthetic. I picked up 7 bottles of Mobil 1 10w-40 High mileage (its on 20w-30 dino now)...

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20W-30 oil? Never seen anything like that. Are you sure it isn't 20W-50???

As far as flushing goes, I wouldn't bother. But you might want to consider an Auto-RX treatment (see the "Additives" forum for many Auto-RX threads) if you really want to make sure your engine internals are cleaned up.

 

[Kingsly]

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20W-30 oil? Never seen anything like that. Are you sure it isn't 20W-50???

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Sorry, I misread the maintenance record. 10w30

 

[wavinwayne]

I'd skip the flush, as most everyone else has suggested. Just switch straight to synthetic, and run a couple of abbreviated oil change intervals.......OR, run a couple of Auto-RX treatments before switching to synthetic.

 

[PT1]

No flush needed......that would be a waste of $$

 

[ThirdeYe]

I'll concur with everyone saying you don't need to flush. I'd recommend switching to Synthetic and seeing how your engine takes to it, and drain it at the recommended interval of 3k/3mos. then run it longer on the next OCI. The only thing that would cause a leak is an already faulty seal. The oil itself doesn't cause leaks.