Man, If I hear one more shade tree "expert" remind me that you shouldn't swap between Dino oil and synthetic, I'm gonna puke.

It's oil. Get over it. If swapping between high quality synthetic or "normal" oil is gonna make your seals leak, they were on the verge anyway. Am I right?

Can I have a genuinely well-informed soul put this myth to rest for me one way or the other?

Thanks,
Scott

I put Mobile1 synthetic in my Geo Metro and had a 1qt puddle under my car every day after work until I changed back to Dino.
Yes, it leaked oil anyway, but not a 1qt puddle while shut off every day for a month until I changed back, when it went back to 1qt between changes, no puddle.
And no, the drain plug was not loose, but I did check it. It had one o'them white plastic gaskets on it (forget now what that's called), which seemed fine. And I did nothing but change the oil to synth and back. That was in ~1992, so there are more additives in synth, and more advances in seals since then, I'm sure. I don't know from where it was leaking.

I use a blend in my car now. Metro is long gone.

I`d say with "good seals" no leak ,no problem ,but with "leaky seals" it may leak quicker....
got Mobil 1 synth in both my daily driver and the bird....
yes the bird has a slight leak around rear main ,but not any more pronounced than with 'regular oil'...I actually tried a thicker oil (thicker regular oil than my 'normal ' regular ) for a short period to see if I`d stop the leak, but all that happened was I ran very high oil pressure, didnt dare to keep it that thick, never had time to check for the leak, since it scared the c*ap out of me reading the pressure gauge...! :rolleyes:

Scott...I hope you have your barf bag handy!...I don't think it's correct to mix synthetic oil with conventional oil. Besides, synthetic oil is way too costly and far too thin!...Perhaps we should get the myth busters to test these oils out in a nonconventional way. :p

Of course, not mixing it in the crank like a 50-50 mix of antifreeze, I don't see how going from one type to the other will make the seals leak. Syn oil is more apt to leak around seals because it's thinnner. The amount left in the oiling system and general internal residue isn't enough to make a difference as far as the definition of mixing the 2 oils. And I don't like dirty oil to begin with, so whatever oil is in the crank will never live there long enough to make a difference.

What's up with the engine?

My bird leaks in a few normal spots anyways, and its minor and predictable, like clock-work. I've learned to know exactly what size puddle she'll leave over 3-5-7 days.

If using synthetic will change that known standard, it would cause me to have to learn her pattern all over again!! :p

Scott,

I have been using synthetic oil for over 25 years. 100% synthetics are compatible with conventional petroleum based oil and vice/versa.

There is only one reason engines leak oil after switching to synthetic - the oil seals were already going bad and the synthetic oil just brought it to a speedier result due to the excellent cleaning properties of synthetic oils. Vicosity (thinner) has nothing to do with synthetic oils leaking more - all oils have to meet the same SAE specs. Leaking is directly related to the condition of the engine seals.

The synthetics clean so much better that they will cause a high mileage engine to start leaking. I have recently switched my son's high mileage 4 cylinder engine to synthetic. It does not burn as much oil as it did when we first purchased it - it does not leak any oil.

Not just my opinion - well documented facts.

Tom

I have used mobile one in my cars exclusively for 15 years now. Unlike the earlier vehicles, these have not develop engine wear problems. The car I bought well used with 160k miles on it sucked enough mobile one past the guides to puff on start up but it never got worse. I gave it away with 230K running strong.

The Taurus we have has 80K miles using mobile one and burns insignificant oil between changes which I do at 3K intervals. In my older beater truck, I don't think I could pour mobile one in fast enough to keep it full. At 100K that vehicle suffered a stuck lifter and was heavily varnished inside. At 80K miles it was always down 2-3 quarts at 3K miles using dino oil. That was fed dino oil since new.

On a new engine, I would break it in with dino for the rings to seat. Then I would use mobile one from then on. I don't believe there is harm switching from one to the other and back, but I see no reason to run dino oil after the rings have set.

Nothing but the oil grade and type recommended by GM in mine. I've used conventional Pennzoil exclusively for over 35 years now and have never had an engine out or repaired. We've put almost all of the 1.2 million miles of our vehicles on Pennzoil. My current GMC's 350 is at 262,000 and uses about the same oil between changes as it did when new. Every 2,500-3,000 they all get fresh clean oil and filter. Synthetics might be great but when something works I don't fix it.

That's why I know so little about engine rebuilds. I've never needed to.

It's not just cleanliness, which is from detergent additives. There are also additives to keep the seals properly... ummm sealed.
Well documented facts
may show that synth oil needs additives to swell the seals. Dino oil either does this by nature, or for some reason already had these additives while the early synths did not. Newer seals are designed to not rely on these additives. Most of this info is available on Google, some of which might be reliable

I also would like to add that early Mobile1 was incompatible with Slick50, which i must say i abhore anyway, but still... It Will turn to gel, as warned by the Mobile1 rep at the shop I once worked for (when i had the Geo). Mobile1 also settled a class action suit regarding sludge buildup in the avaiation field.

edit: sorry for undocumented snow-tech. I've been looking this cr@p up for too long already to provide links now.

Personally used Mobil 1 in the winter months for years in one vehicle for easy starting. Switched back in the spring.

It may lubicate better, I will leave that to the experts; however got over 500K miles on shop truck on conventional oil before retiring for rusted out body (ain't salt on the roads grand?). Cylinder head had never been off the engine, and engine was still in excellent shape. Did not burn any oil between changes. Key IS to change the oil AND filter.

Jon.

I have to agree with Tom 100%

Typically they used to recommend that you add one quart of high end synthetic to clean out the system. Then you change the oil and filter. And then change the filter at regular intervals, but only change the oil once a year or 25,000 miles.

Now as even the Synthetics have improved, you don't even have to do that to change it over. But it's true that quality synthetics will clean out the system. Conventional oils will over time make seals brittle and the seals will shrink. This is not the case with quality synthetics. They prolong the life of the seals, and keep them pliable much longer. But if the damage is done, yes it will clean out the years of deposits and you may see more leaks because of the poor condition of the seals or gaskets once you change to a quality synthetic.

A high end synthetic is usually cheaper. Especially once you factor in the improved performance, improved gas mileage, and the longer life of the engine, with far superior protection of it's moving components. You change the oil once a year, and the filter say 3 or 4 times a year. Conventional oil you change at least 8-9 times a year and the filter at least that many times (based on the 25,000 miles a year changing conventional oil at every 3k)

The quality synthetic oils come in about any viscosity you would want. Heavier weights for hotter climates, and lighter viscosities for colder climates. The beauty of a quality 100% synthetic, is that you can use say a 0W-30 or a 5W-30 where you would usually use a 10W-40 or a 20W-50 weight oil. The motor produces more HP, the motor pushes the oil easier and more efficiently, and all this with superior protection. So you can use any viscosity you want in either conventional oils or quality synthetics.

This is why in the last 5 years every major oil company has all of a sudden come out with Full synthetics, synth blends and the like, as well as in the last 10 years there are at least 2-4 additional companies who have come out with 100% synthetics, not to mention the pioneer synthetic brand that has been around for over 25 years. Yes, most of the shows you see also praise the benefits of a quality synthetic lubricant. Not just the oil, but gear oil, tranny fluid, antifreeze etc you name it, and it's out there in synthetic form, and will out perform it's conventional counterpart.

Now is it right for everyone? No, like Jim said, if it isn't broken, don't fix it. And some of out car are not driven that hard or especially that often. The fluids get changed more often than needed etc... so it would not be a huge benefit for many of our birds for example.

For me, I saw the benefits early on, and did the math for myself... and I know that many of my cars would never have seen 250,000 - 315,000 miles unless I had switched them over to a high end 100% synthetic as soon as I bought them. All my cars are used, and who knows how well abused before I got them...

So if it leaks more, it's because the problem was there before, and plugged with sludge and build up.. now that it's clean, the poor seal is just that, a poor seal. Synthetics will in most cases help recondition the seal, but only so much...

Yes, I've done a LOT of reading up on both sides of the issue... and even between brands of Synthetics, and yes... there is a big difference.

Just my opinon... but I feel better using it than I would using conventional oils.

Brett - 67 Drop Top 455! (sorry for the long post!)

Thanks for your replies gentlemen!

Jim and I are on the same wavelength: When I use dino, I use Pennzoil.

My one piece of compelling anecdotal evidence is that full synthetic REALLY helps out dry starts on both my 2000 Honda Civic and my 68 Bird. An easily AUDIBLE difference.

At $1.00 more per quart, the Extended Life Mobil 1 seeems to be a good value over the "normal" Mobil 1.

I'm having a new engine put in my Bird. (Work should start on it in a few days.) AFTER the break-in period, what weight of Mobil 1 should I use? 10W-30? 10W-40?

Thanks again,
Scott

Brett, I'll switching to syn. this spring in my bird the break in period on my new engine is just about over.

So if I can run my bird on the same oil all summer how often should I change just the filter ?

A side note a few years ago I bought a 89' Buick Lesabre with 172,000 and before I quit shopping Wal-Mart they were the ones who changed my oil.
Only using the bulk oil whatever it was they had I sold that Buick with 315,000 and it still ran like a top.
I was told once that as long as you use whatever oil had the rating the manufactuer recommended you'd be fine.
The oil issue has alot of variables in it conv. oil vs. syn. oil which if I remember right Smokey Yunick was pushing back in the 80's.
Well I bought some syn. oil from a auction last new from a dealer who was going out of bus. so I'll try it this spring.

Doug, for oou cars that get less use and are for the most part cruisers... personally, I'd extend the break-in period oil wise just to make sure the rings seat well. I've heard different things depending on what type of rings you use etc.

But, when your ready, and again, depending on the oil manufacturer (I use Amsoil) go by their specifications. But say Amsoil, I would change it with the oil, and again after about 1K and then at the end of the season. The next summer/season typically you'd only change it once...

Again, a lot of variables, but just watch the oil, coloration and do what feels best for you.

Brett - 67 Drop Top 455!

Yea that's the brand I bought I just couldn't think of it at the time.

The last time I bought oil for the bird the synthetic blend was just slightly more expensive than the Penzoil I buy so I bought some. I change the oil at regular times a year with low miles in between. Pete