I was told by the auto parts guy, that if your car was started out on regular oil and you switch to synthetic it will cause your seals to leak, since it is more oily. He told me I should switch back to regular, since I made the switch already and my seal is leaking. I have 253k on my engine and switched to synthetic at about 147k. Should I bother switching back? or will something drastic happen? Thanks!

 

 

All I can say is that my leak from the timing chain cover appears to be gone since switching back to regular oil. I was losing significant amts of oil between changes and this was going on for about a year I was on the synthetic stuff. Switched to synthetic at about 65k miles and switched back to regular oil about 83k miles.

 

I hope this wasnt covered in your oil analysis. To tell you the truth, I have been so busy during your whole testing, I have not even read any of it. Sorry Bill.

 

the leaking "concept" is a myth..if u have a seeping/slow leak w/ dino oil..with syn it's going to leak a lot more. syn have smaller uniform molecules compared to dino that have different molecule size. if your seals are good and not leaking with dino it's not going to leak with syn..if it's leaking with syn that mean your seal(s) was going/gone already but it was not leaking bad enough for dino.

also syn tend to have more detergent in the oil...it may loosen/clean up carbon that was acting like a plug around the seals.

u can switch back and forth w/o worries.

 

Thanks Dan, time to head to the auto parts and switch.

 

I think your mileage has more to do with the leak than the oil. Seals don't last forever.

 

Ditto. You have run synthetic for 100K, it's clear it didn't cause your leak. In fact, seals run with synthetic oil tend to last longer as lomg as they were in good shape prior to the switch. I'd be shocked if swithing to a dino oil actually "solved" your problem for long.

 

The dino causes build-up which plugs little scratches in the cylinders and turning parts... If you switch to syn. you will wash the residue away and oil will now travel in these micro grooves... To my understanding neither cause any more damage to seals then the other but the residue crack sealing properties of the dino oil cause the micro scratches on the crank and cams to be sealed.. on syn. these grooves now act as mini sanders and wear the seal faster...
I personally use Dino oil in my cars...

Note: English was my worst subject and I can't spell worth a damn.

 

so whats the point of syntetic then. i don't get it. from read your guys posts i found no good in it.

 

The point is easier cold starts, better high temperature protection and film strength, increased fuel efficiency, longer drain intervals, etc...

Using synthetic oil in an engine that has been regularly maintained and in good shape is no problem. This thread was more slanted towards why synthetic oil can be a poor choice in an engine that has been negelcted or maintained poorly with regards to seals.

 

oh ok i see thanks