synthetic oil seems to be stopping/slowing leaks

[girr tory]

Does anyone have a comment on this phenomenon?

 My roomie's 98 legacy had a seal leak in passenger side front axle at trans.  I changed (at a shop#1) the trans oil which was very cruddy, with synthetic 75-90 wt. transmission oil.  That shop#1 and another, (shop#2) that diagnosed the same seal leak, both confirm there is no leak now.  This two months after the oil change.

 

Also,,,,

Four months ago the same shop#1 swapped the 2.2 engine with a JDM long block.  I watched it closely and found a head gasket leak at passenger side bottom front area. A small one but a leak.  And a leak at driver side tappet cover.  Shop #2 picked these up too, at the same time as the above seal . When they did the swap they used 5-30 synthetic oil.  The first little while we just drove it in the city.  The exhaust would catch the leaks and you could smell burning oil at times. The last six weeks there have been highway trips, and ski trips - extended 60 - 70 mph runs up 4% - 6% grades in 4th gear.  The car has been worked and is working well.  The thing is .. the smell is way less, there is no oil loss, yes a little leak but maybe less?  I never was able to determine a rate of leakage. The coolant is not cloudy. Shop#1 put a dye in the oil and say there is no trace in the coolant. 

 

Is there any record of gaskets, seals, o rings and such swelling from the current crop of synthetic oils?  Maybe some kind of mechanical seating from thermal stress from a hard workout?

Where is the research on this?  Discuss,,,,

[1 Lucky Texan]

(how does the trans shift with the synthetic gear oil? many people report problems with clashing unless running conventional GL-5)

 

www.bobistheoilguy.com may be an interesting place to find some info on your question.

 

There have been anecdotal reports in the past of use of synthetic oil in engines previously lubricated with conventional oil developing leaks. But, if modern synthetic formulations include any additives designed to help gaskets/seals be more pliable or expand, that leads to the possibility of reduced leakage.

 

or perhaps after the engine work, there was just some residual oil being cooked-off the exhaust?

 

maybe others can comment with better knowledge.

Edited February 4, 2017 by 1 Lucky Texan

[idosubaru]

It could be related, it would be an outlier. Varying symptoms are common, oil choice making a significant difference is not.

 

Unlikely related to the oil. Could switch back under identical circumstances, to confirm. the oil *change* would be more likely the culprit than the oil *type*. Two totally different things but most people are terrible at living or operating under the reality (even if they know it's true) that correlation does not mean causation. They are quick to assume.

 

Intermittent leaks are common. I've seen used engines use oil the first oil change or two and then subside. Maybe the previous oil was an undesirable weight, overfilled, or ancient or contaminated, maybe the leak(s) will return in the future and were previously intermediate. Maybe the leak was present for years but intermittent and rarely noticed. Maybe the car is driven significantly different than before or time of year dependent (typical for college students for instance). Maybe the diff vent tube was clogged and was dislodged during work. Assumptions, history, change in usage, environment, vehicle condition...are all highly variable and subject to ambiguity. There's a lot of possibilities.

 

"Suspicion often creates what it suspects".

In general there's a false sense of oil choice importance giving infinite anecdotal commentary and opinions. which makes it easy to see whatever possibility you want to see.