rtd111 Posted April 2, 2006 Share Posted April 2, 2006 91 LS400, 147K miles Short of it: should I do something special or what's the down side of switching back from synthetic to regular engine oil? The long of it... I changed oil about 1500mi ago, changing from regular to Mobil Synthetic. That was the first time I switched to synthetic in this car. Sure run smoother (or maybe because I also have done lots of other work around that time). Perhaps by coincidence, perhaps due to thinner synthetic (and other posts about questionable sealing capability of synthetics) I have had a small engine oil leak for about the last 600+ miles. It may have started sooner given the drip has gotten increasingly noticeable to a small puddle every 2 out of 3 times I drive the car. I checked under the car and sure enough, there is oil seeping thru, a drop at a time, from the rear main seal (kind of like the first pic at http://www.lexls.com/tutorials/transmission/removal.html). I want to delay the work a few months plus am wondering if going back to the thicker regular oil might help slow down or even stop this problem. Anything special I should do before I switch back to regular oil? I plan to drain, put new oil filter, and fill with 5W-30 MaxLife. Many thanks. Quote Link to comment Share on other sites More sharing options...
dcfish Posted April 2, 2006 Share Posted April 2, 2006 91 LS400, 147K miles Short of it: should I do something special or what's the down side of switching back from synthetic to regular engine oil? The long of it... I changed oil about 1500mi ago, changing from regular to Mobil Synthetic. That was the first time I switched to synthetic in this car. Sure run smoother (or maybe because I also have done lots of other work around that time). Perhaps by coincidence, perhaps due to thinner synthetic (and other posts about questionable sealing capability of synthetics) I have had a small engine oil leak for about the last 600+ miles. It may have started sooner given the drip has gotten increasingly noticeable to a small puddle every 2 out of 3 times I drive the car. I checked under the car and sure enough, there is oil seeping thru, a drop at a time, from the rear main seal (kind of like the first pic at http://www.lexls.com/tutorials/transmission/removal.html). I want to delay the work a few months plus am wondering if going back to the thicker regular oil might help slow down or even stop this problem. Anything special I should do before I switch back to regular oil? I plan to drain, put new oil filter, and fill with 5W-30 MaxLife. Many thanks. Do not switch back to dino. The seal has to be replaced no matter what. Deal with the slow leak until you can get the replacement in there and stick with syn oil from here on out. ;) Quote Link to comment Share on other sites More sharing options...
alsalih Posted April 2, 2006 Share Posted April 2, 2006 Not surprised with what happened. I just had a very similar experience with my 98 (read my posting). Anyway, syn is thinner and will leak through worn or weak seals which normal oil wouldn't leak through. I went from a perfectly dry car to massive leaks 4K miles after switching to Mobile 1 and I switched right back to regular oil and I'm pleased to say that 2K miles since the switch back my seals have swelled back and the car is no longer leaking. To answer your question, nothing special needed just switch back to regular oil or even better use the one made for vehicles with higher miles which has additional additives that will help seals swell and maybe stop your leak. Give it 2K miles before you look for any improvement. Good luck. Quote Link to comment Share on other sites More sharing options...
monarch Posted April 2, 2006 Share Posted April 2, 2006 I'd use a slightly heavier oil - a 10W-30 or 10W-40 and a high mileage oil since these oils have a seal swelling additive. In tropical countries where there are no government fuel economy standards, Toyota approves of the use of these higher viscosities so they shouldn't hurt the engine and will help slow the leak. Quote Link to comment Share on other sites More sharing options...
SKperformance Posted April 2, 2006 Share Posted April 2, 2006 AGree use a thicker oil but don't switch back. Don't add stop leak agents either. Quote Link to comment Share on other sites More sharing options...
Bill H Posted April 21, 2006 Share Posted April 21, 2006 91 LS400, 147K miles Short of it: should I do something special or what's the down side of switching back from synthetic to regular engine oil? The long of it... I changed oil about 1500mi ago, changing from regular to Mobil Synthetic. That was the first time I switched to synthetic in this car. Sure run smoother (or maybe because I also have done lots of other work around that time). Perhaps by coincidence, perhaps due to thinner synthetic (and other posts about questionable sealing capability of synthetics) I have had a small engine oil leak for about the last 600+ miles. It may have started sooner given the drip has gotten increasingly noticeable to a small puddle every 2 out of 3 times I drive the car. I checked under the car and sure enough, there is oil seeping thru, a drop at a time, from the rear main seal (kind of like the first pic at http://www.lexls.com/tutorials/transmission/removal.html). I want to delay the work a few months plus am wondering if going back to the thicker regular oil might help slow down or even stop this problem. Anything special I should do before I switch back to regular oil? I plan to drain, put new oil filter, and fill with 5W-30 MaxLife. Many thanks. At 75k I noticed on my 1997 LS at 3000 miles between changes I heard lifters ticking. Checking the oil I was down 1/2 a quart. I noticed this for two more changes. I then switched to Mobile 1 and now only change every 5k without and sounds or loss of oil. I get the change at Wal-Mart and for a Mobile 1 change they charge $36 bucks. I would stay with the mobile 1 and fix the leak. JMO Bill Quote Link to comment Share on other sites More sharing options...
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