I switched to Mobil 1 and now I have a slight rear main leak....

[Anthony 94 525i]

I switched to Mobil 1 and now there is a slight rear main leak..mechanic said to use a gunk brand sealer which may work......not having a good week..so far I installed a new belt for coolant pump,new heater hose,and a screw in my front tire, and now the leak.........anyone have this leak problem switching from traditional oil to synthetic? to fix rear main seal big job? help....

[Bill R.]

I switched to Mobil 1 and now there is a slight rear main leak..mechanic said to use a gunk brand sealer which may work......not having a good week..so far I installed a new belt for coolant pump,new heater hose,and a screw in my front tire, and now the leak.........anyone have this leak problem switching from traditional oil to synthetic? to fix rear main seal big job? help....

[632 Regal]

but i dont think thats what caused the leak. DO NOT USE additives! I'm not sure but think all you have to do is drop the oil pan and trans to replace the seal. Check for leaks coming from other places, did the mechanic confirm that it is the main for sure?

[Dick Schneiders]

I have switched over many old and high mileage cars from regular oil to Mobil 1 and only once did I ever have any leak soon after the switch. That one time, the leak was a very small one and I never did figure out where it was coming from. In fact, after a few weeks of driving the car with the leak, it simply stopped leaking and never returned! This was over a year ago. I really don't know what happened. Perhaps the Mobil 1, with its better lubricant and cleansing action, initially removed some crud that was sealing off this small oil leak. Then, perhaps the Mobil 1, after being in contact with the seal, which was probably dry from being "protected" by the crud, moistened the seal and allowed it to swell back up to plug up the leak. I have read in several places that the modern Mobil 1, unlike the first formulas, have a very good seal lubricant in them.

Anyway, that is a guess on my part.

Dick Schneiders


I switched to Mobil 1 and now there is a slight rear main leak..mechanic said to use a gunk brand sealer which may work......not having a good week..so far I installed a new belt for coolant pump,new heater hose,and a screw in my front tire, and now the leak.........anyone have this leak problem switching from traditional oil to synthetic? to fix rear main seal big job? help....