synthetic in leaky engine

[MustangGT]

I have an older pickup that seeps some oil, not enough to have to any oil between changes though. If I used Mobil one for six month oil changes do you think it would likely begin to leak more oil or probably the same amount? I like the idea of extended drains and mobil one would be my choice. Any thoughts?

Thanks

 

[csp203]

Had a 85 chevy with a small bloack (305) with a small leak at the rear main. I bought it on its 2nd engine with god knows how many miles. I put rotell T 5w-40 synth in it. The small leak turned into a large leak.

 

[Hankrr]

I had an old Buick (305 V8)that leaked a lot. I still used Mobil-1 but used a thicker weight. 15W50 towards the end. *car went to 350k* Still leaked but not nearly as much as say a 5W30.

 

[andyfish]

quote:

---

Originally posted by MustangGT:
I have an older pickup that seeps some oil, not enough to have to any oil between changes though. If I used Mobil one for six month oil changes do you think it would likely begin to leak more oil or probably the same amount? I like the idea of extended drains and mobil one would be my choice. Any thoughts?

Thanks

---

Stick it in and try it out. You'll never now till you try it as there are an infinite amount of variables between vehicles.

 

[Ray H]

Two thoughts:

1> Synthetics, both Group IV based as well as Group III based, contain esters in the blend. The original intent of the ester content was to promote controlled elastomeric seal swelling to counter the shrinkage when traditional PAOs were used as motor oil that resulted in synthetics' notorious leakage problem. (Solvent refined Group I based motor oil lube stocks have cyclical ring "aromatics" left over from the original crude oil. These aromatics have a solvent quality that promote seal swelling. Unfortunately, aromatics are not good lubes. However, in addition to their seal-swelling qualities, esters are superb lubricants in their own right because they're also polar molecules which aid cleaning and adhere by charge attraction to the molecule-thick oxide coating present on all metal surfaces - unforeseen functional bonuses...)

But, before you race to dump in a full changeout of Mobil 1 in your tidiness-challenged engine...

2> Since synthetics are "slipperier" than their Group I solvent refined counterparts, normally a sterling quality, that extra lubricity can often allow leakage past seal flaws which would otherwise be impenetrable, or nearly so, to conventional motor oils.

If you're confused by these contradictory synthetic qualities, it's evident you're thinking. (always dangerous...) I'd venture if your engine is already leaking with conventional oil, it'll be at least as bad (and likely even worse) with synthetic motor oil until you track down and repair the leak(s).

 

[TC]

Good post, Ray. A compromise would be to use one of the synthetic blended high-mileage oils. Maybe add a couple thousand miles to your oil change intervals -- not as much as a full syn, but helpful nonetheless.