can synthetic oil be detrimental?

enotslim · Post by **enotslim** » 23 Aug 2017, 17:12

I apologize in advance for what is probably an annoying question. But ... I am returning to doing oil changes on our cars after letting someone else do it for 30 years. In the old days ... there were warnings that the "new" synthetic oils could damage cars that had been maintained on dino oil. Perhaps because the relatively harsh early formulations could damage seals and/or remove "stuff" that shouldn't be there but that actually performed a sealing function in older cars? From reading it seems these issues are largely a thing of the past (like me) but I just wanted to check to avoid heading down a wrong path. What concerns if any should I have about using synthetic oil in our 1998 V70 T5 wagon and 2004 XC70 that have only seen dino oil? On the other hand, is it likely that synthetic oil will be an improvement beyond the ability to go longer between oil changes? Without a significant likely improvement the additional cost may not be worthwhile.

The 1998 V70 T5 was driven over 10 miles with essential no coolant last winter (the story is in the MVS forum). Miraculously, the engine seems OK with a new radiator, but I do worry that leaks lurk just below the surface. In this case is there a greater risk that switching to synthetic oil may cause problems with seals or otherwise?

The 2004 XC70 has no similar background or concerns.

Post by **bmdubya1198** » 23 Aug 2017, 18:37

I'm not too big of an oil guy, but I have a good idea about it. Synthetic oil is much more resilient to heat, and especially considering your cars are both turbocharged, I would recommend switching. It is also less prone to breaking down and thinning out over time. Yes, you can do longer OCIs as well.
I don't think there is any danger to seals by switching from dino to synthetic. You'd probably do more damage by switching weights (but again, minimal risk unless you've got a seal that's already ready to let go).
I switched over my car to synthetic at 169k miles and I have not experienced any problems that I could correlate to the oil. I was honestly concerned that the car was still running conventional on a turbo motor at that mileage.

Post by **abscate** » 23 Aug 2017, 19:12

Ive moved three cars from dino to synthetic with no additional problems, leaks,burns, etc. Two of them were high mileage, over 100k

Post by **rainman** » 23 Aug 2017, 19:43

2000 V70 SE with 210,000 miles. I was just wondering if I should continue to swap out 3 quarts of Mobil 3309 at least every 3-4 months? This was something I came across on You Tube DIY Robert. The reason his method seemed so appealing to me was due to his emphasis on "Not Shocking the transmission" with a full remove and replace. Instead it exchanges in percentages where over time it might look pretty red and healthy. It seems like the perfect balance to improve,extend, and preserve, with out trashing it completely. And So, this is what I have been doing for almost a two years now, and my question is, am I wasting my time in continuing to do this or could this theoretically only be of benefit? I've reset the fluid counters and adaptation a hand full of times, only because statistically, I thought the quality of the fluid would have to be improving?
Thank You MVS, and for all your help in the past.

Post by **oragex** » 23 Aug 2017, 20:06

I switched on synthetic on two cars both with 100k miles, a Honda and the S60. Both started drinking oil like crazy for the first couple thousands miles, so I kept adding oil. I've also replaced the filter after about 500 miles. With time both engines stopped drinking oil at all, not even dropping on the dipstick between oil changes.

Post by **mrbrian200** » 23 Aug 2017, 20:44

Changing 3 quarts every 3000 mi. on the transmission ad infinitum seems way overkill unless you're towing or live up a mountain. If it were me, after doing 4 in a row spaced apart by 3000 miles I'd drop back to once a year or 15,000 miles whichever comes first. Just pull the dipstick once in awhile and check fluid quality and level. Which you should be doing anyway.

Post by **tryingbe** » 23 Aug 2017, 22:10

My 85 GLH, 94 855, and 00 Insight all used synthetic oil.

The Blue Whale · Post by **The Blue Whale** » 24 Aug 2017, 07:19

Its the oil filter you should worry about with the switch to synthetic. Make sure to get one that can last as long as the oil between changes. I started using synthetic but failed to upgrade my filters and had one near collapse and one come apart in my hand when I changed the oil at the longer intervals. Switching to one designed for synthetic worked out I am happy not changing my oil as much. Run it in 06 xc90 260000miles and an2011 xc60 125000.

Post by **wizechatmgr** » 24 Aug 2017, 13:53

As long as the oil meets the performance specs of the application you're using it in, and the manufacture is honest with their test results, you should not have any issues.

Occasionally folks may experience minor oil leaks, but this is due to seals that likely should be replaced due to age/wear.

The only "real" negative to synthetics is cost. If you choose to attempt longer oil change intervals, make sure to make MORE frequent oil level checks on the dipstick.

I know I'm going to catch hell for this, but I use Rotella T6 and the rest of their line. I've used it on every engine I have had for years. There are rumors of the extra additive packages potentially causing issues to catalytic converters - I haven't experienced this in the 300k+ miles I've driven on it. Then again, I've never had a car burning/blowing oil with it in it either... Been trying LiquiMoly lately and really like it. It is relatively cheap & the jug even has a pour spout!

https://www.amazon.com/gp/product/B005H2SHS8

Post by **bmdubya1198** » 24 Aug 2017, 15:36

wizechatmgr wrote: ↑24 Aug 2017, 13:53 As long as the oil meets the performance specs of the application you're using it in, and the manufacture is honest with their test results, you should not have any issues.

Occasionally folks may experience minor oil leaks, but this is due to seals that likely should be replaced due to age/wear.

The only "real" negative to synthetics is cost. If you choose to attempt longer oil change intervals, make sure to make MORE frequent oil level checks on the dipstick.

I know I'm going to catch hell for this, but I use Rotella T6 and the rest of their line. I've used it on every engine I have had for years. There are rumors of the extra additive packages potentially causing issues to catalytic converters - I haven't experienced this in the 300k+ miles I've driven on it. Then again, I've never had a car burning/blowing oil with it in it either... Been trying LiquiMoly lately and really like it. It is relatively cheap & the jug even has a pour spout!

https://www.amazon.com/gp/product/B005H2SHS8

I haven't used Rotella in my Volvo, but I've been thinking about it. It's designed with a heavy duty additive package obviously for heavy duty diesel trucks, and although Shell says it's not meant for gasoline powered cars, that could only be a good thing that it's "heavy duty," especially if you put a lot of miles on your car or you're like me and drive your car a lot harder than you should.
It is API SM, which is above the standards for our Volvo 5 cylinders, which I think is SH or SJ.
I wouldn't be too worried about the cat being damaged by oil unless you have leaking valve stem seals or rings. So that really shouldn't be a concern.