bship

I should have known better but when I had my oil changed recently before a track weekend the mechanic asked what oil I used I said Kendall 20-50 he said they used red cap MOBIL 1 in all their race cars and I should try it. I mentioned I had heard that older engines could begin to leak if using synthetic. He said if I had no leaks now I wouldn't have any problems with synthetic. Well he was wrong! I have never had any leaks and now I have at least 3 after running it for 2 track days. My question is have I done damage to the seals or will I be leakless if I go back to my conventional oil???

Thanks

jlkline

If you do a search Mobil 1 and oiled leaks on this forum, you'll have a pretty good answer. I switched back after finding leaks a few months following M1 installation, and this eliminated nearly all of my leak problems, with the exception of the oil lines going back from the fender thermostat to the engine, and the short flexible lines coming off of the front oil cooler.

From now on, its dino for me!

sschmerg

Mobil 1 does not cause leaks. The leaks were already there, they were just covered up by deposits and thicker oil.

Once you use the Mobil 1, its detergent will clean up some of those deposits and reveal further leaks, so switching back will not entirely solve the problem. Mobil 1 is a superior oil though, so if you can spare the expense, you might want to fix the leaks and use Mobil 1 regularly.

-Sean

jlkline

I think some philosophy is warranted here..... If an engine has an oil leak that doesn't leak, is it a leak?

As my personal testimonial, I had 11K miles on a one year old rebuild of my daily driver. (no DE ever) Up to that point, I ran dino (Castrol 20-50) changing it every 3000 miles with no engine leaks. After reading a lot of tech articles and forum threads, I decided to bite the bullet and switch to Mobil 1. After 2 months I observed leaks developing in multiple engine locations...case halves, valve covers (930's), etc. which got increasingly worse over the next several months.

I switched back at my 1st valve adjustment interval after the rebuild (15K miles) and the engine leaks stopped and have not reappeared after 6 months so far. End of story.

Douglas_T

Interesting...Any other imput guys?

sschmerg

Well, I have used Mobil 1 in my car for the last 2 years, and it has not leaked a drop. I think the previous owner used Castrol. The car only has about 25k miles and has been very well maintained.

We had a '78 SC 3.0 rebuilt about 3 months ago, and it was filled with conventional oil (as is standard practice after a rebuild). It has not had its first change yet, but I can already spot some seepage and some dripping on the heat exchangers. Putting Mobil 1 in this thing would probably sprout leaks all over the place! (We are getting these leaks taken care of under warranty).

Air/oil cooled motors are difficult to stop leaks on, as they expand a great deal when hot, and have to have tolerances that can handle that expansion.

So, I guess it all depends on how well the engine is sealed. I personally would like it sealed well enough that I can use Mobil 1, because I think it's a great deal better than conventional oil.

My 2 cents.

-Sean

pjc

I had slights leaks on a '76 911 run on a 20:50 which turned into rivers with Mobile 1. My solution was to try and cure the leaks but some proved stubburn and I have now switched back to 20:50. Still have some dampness but not so much. I also have a 993 which has been run entirely on Mobile 1 or equivalent and that also started some leaks - which I have managed to cure.

Those leaks onto the heat exhangers can be difficult to find let alone fix.

Drew Theodore

This subject is discussed on all automobile boards and there is no clear answer to which is best if you change oil less than every 3000 miles.
I change every 1000 miles because I do not put but 1000 miles a year on the car. Even the high temperatures in a 911 cannot break down dino oil in 1000 miles. Save your money and use a good quality dino oil.

KC911

Having purchased my '88 (with 46K on her at the time) a little over a year ago, I switched to Mobil 1 15W-50, and within a few months and a couple of thousand miles I began to see an occasional drop of oil on my garage floor. I switched to Castrol 20W-50, and the leaks have stopped. In my case, my motor is virtually spotless (...many hours of cleaning), and it's not an issue with not being able to see the leaks. I no longer see them...'cause they're not there! I had also read the caveats about switching back to dino (to stop leaks which appear after using synthetic) as being ineffective, but in my case, w/ dino...she doesn't leak a drop!

sschmerg

I like to use Mobil 1 15w-50 just for the added protection. The extra cost is not an issue because I don't put many miles on the car, and only have to change it a couple times a year.

If it starts to leak, then I'll think about going back to the conventional oil!

-Sean

Ed Bighi

Some cars will leak with Mobil 1, while others not. Mine does not. But to clear it up, I'll say again what sschmerg said. Mobil 1 does not cause oil leaks. And while the detergents in Mobil 1 will clear up deposits, what makes the leaks start is the flow rate of that particular oil at lower temperatures. You see, what makes Mobil 1 a great oil for year round use is what helps it go through weak seals. Even though it is a 15/50 oil, it is far better than other oils of the same weight at startup and low temps, while still having as good if not better hot temperature properties. It just really flows. For example, cold start a 911 running Castrol 20/50 on a 40 degree morning and then do the same with the same car running 15/50 Mobil 1 and the difference is clearly evident. The superior flow rate at even much lower temperatures is what shows the leaks. Sure one can use the argument that if it does not leak, the is no leak. We can get philosophical about this, but what it boils down to is basic physics. For example, a pipe connection that leaks water, will probably not leak molasses if it were present. Of course I used extremes in that example, but it explains why Mobil 1 will suddenly start leaking in an otherwise dry motor. And this does not mean that Mobil 1 has the viscosity of water. It just flows a heck of a lot better than a dino 20/50 when cold. Also, the cold viscosity of 15/50 Mobil 1 is 15, which is already lower on the cold side than the usual dino 20/50. That is actually a good thing because it makes the oil better suited to a wider variety of ambient temperatures. I just with I could get the 5/50 Mobil 1 in the US, since that would have an even better range.

JPhillips-998

Okay, here's my take...OIL LEAKS FROM MOBIL 1 ARE GOOD!. Why? Because if your engine never leaked on traditional oil and begins leaking w/Mobil 1 that tells me that Mobil 1 is finer and getting into the recesses that traditional oil doesn't reach.

Logic says that if the mobil 1 can get to the far recesses of the engine that traditional oil can't then it's mobil 1 for me. I just put a cardboard sheet under car and let it leak.

jet911

Question: For the winter, I've been running Castrol 10/30. I have a small leak from the lower valve cover nuts (it is not bad, just a very small drop on the floor on the left side). It leaks less in the summer when I change to 20/50 (a drop every other day or so). If I change to Mobil 1, 15/50 could I expect the leak to increase, stay the same or decrease. From what I've been reading above, it would appear that the leak would stay about the same or maybe even decrease to about the same as when I run the 20/50. Opinions would be appreciated as I'm about ready to change the oil for the summer driving season.

Regards,
Jim
'86 911

jlkline

JPhlillips-998, I guess you've never experienced the embarrassment of a smoking engine compartment caused by oil dripping on to the heat exchangers while the hot babe in the car next to you at the light looks smirkingly on. (Me neither, thank God, but I've seen it happen)

The additional protection of Mobil 1 or any other lubricant at the expense of a drippy, wet Porsche motor, a creature designed / engineered with elegance and precision, is not a trade off I'm willing to make.

sschmerg

Take a look at this long-term test of Mobil 1:

<a href="http://neptune.spacebears.com/cars/stories/oil-life.html" target="_blank">http://neptune.spacebears.com/cars/stories/oil-life.html</a>

Holding up amazingly well after over 8,000 miles!

-Sean