went through 2 quarts- oil, in 1100 miles!

[David]

passed dyno inspection 6 months ago, with
extremely low levels.

- just replaced valve cover gaskets
- 10/30 mobil one synthetic
- havent been racing it- normal driving
- obviously its not smoking

what should i be checking?

[90LSCdrvr]

Rear Main. Mine lets out about a quart every 2500 miles or so.

Climb under your car, look at the oil pan, towards the back of the engine, where the Trans bolts up. It'll look all dirty and wet like. This is probably your problem.

When was the last time you replaced the PCV Breather and Valve? Sometimes, Pressure can build in your cankcase, because the PCV Breather is clogged, which will force the Pressure through a weak seal, usually the Rear Main, and creating a leak in the process.

You may get lucky and minimize the leak by replacing the the PCV Breather(which sits under the PCV Valve, in the back of the lower intake manifold), but once the oil starts coming out of that rear main, it almost never mysteriously stops.

Good Luck

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90LSCdrvr

[Lscman]

Ditto.

[xx_jack]

Originally posted by Lscman:
Ditto.

say guys, i dont know anything about anything--and only offer this as a personal-----and unconfirmed opinion---
mobil one---and all synthitic oil will seek out and penetrate any weak places in gaskets and make a car that otherwise has never leaked oil....begin to leak!!!!---especially old cars with old and fragile gaskets due to age, climate etc.........right or wrong????

-------and that reverting back to reg non synthetic oil will indeed seal up the "leaking" gaskets----except probably for the rear main....though, it should even improve that! again right or wrong?------------

synthetic is super penentrating and that is the reason it causes leaks and should not be used in older cars for that reason unless you want a leaker.!!!!---

again guys i dont know s*** about anything but that is pretty much my experience.!!!!!-

-hope i am not putting out any false info here..that is not my intentenion-----jack

[Lscman]

Jack,
Your claims may be a little overstated with respect to synthetic causing older motors to leak & your conclusions don't cover all the pros and cons or measure their seriousness.
>>I'd say yes, synthetic oils do tend to dissolve gooey buildup out of seals in older motors & that can cause them to leak, in some cases.
>>I'd also say that synthetic greatly reduces friction and will basically cause engine wear to stop.

My conclusion is you can change a couple leaky $5 seals every 10 years on synthetic or rebuild your worn out dino motor every 125K or so. Which is more difficult & costly?? Hmmm. My car with 230K miles needed a front dampener seal that took about 3 hours to change and a rear main seal that I had changed 100K ago when my trans was rebuilt. Cost me about $25 for both. I changed over several high mile cars to Mobil 1 synthetic at 100K+ mi and they are all on the road today with no engine wear symptoms. I change my oil every 25K and I get better gas mileage and virtually no engine wear. Plus, I lay under my car less often. My oil change costs are cheaper due to the extended interval and the 1-3% increase in economy and horsepower is welcome. My cylinders have absolutely NO ridge and hone marks are visible to the top! My motor might go another 230K.

[Guido]

My 2 cents: if you ignore the debate (depends on who you talk to) about synthetic oil's additive package never lasting 25K miles (because that is not synthetic, only the lubricant portion of it is), then I hope you still change your filter per the manual because synthetic won't stop dirt buildup.
What has worked for me is using quality mineral oil and changing it often (max. 4K KM) and use the synthetic where you don't change so often (differential).

Another advantage of changing your oil often is you can monitor engine wear/debris in the old oil and see if there is a trend of anything unusual happening in the engine and hopefully correct the problem before it does real damage. If you wait 25K miles to check for wear, a lot can happen in the meantime.

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'92 LSC, fully loaded... except CD!

[mdcluth]

I'll jump in on this one! The reason why synthetic oil was developed in the first place was to resist thermal breakdown which occurrs naturally in most lubricants. Time and temperatures use up the detergent, ash and other additives that give the oil it's ability to clean, cool, and lubricate. These additives also determine how well it will stick to metal, or get into the pores of the metal. Organic engine oils were improved over the years for better lubrication and cleaning, but can only go so far with avoiding thermal breakdown. This is why you see reccommended oil change intervals at 3 - 5,000 miles.
Synthetic engine oils clean and lubricate better because they invade the pores of the metal better than organic, and they hold their additives better. Just ask any oil recycler. Dirt in oil comes mostly from engine wear, but can also come from poor intake air filtering and a few other minor causes. If you reduce the wear, you allow your oil to stay cleaner, lubricate better, blah, blah, blah.
Those 25K mile oil changes are a direct result of a top quality engine oil and filter combination, and an overall well maintained engine. Some folks might be paranoid about going more than 3K miles without a filter change or oil change. The simple fact is that it can be done, and it ends up saving you a lot of money in oil and filter changes as well as engine wear.
OK - who's next!

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"Lincoln Moves Me"

[90LSCdrvr]

LSCMAN: How hard was it to replace your rear main seal? Did you pull the tranny? Does the flywheel need to come off? Would it be easier to "pull" the motor, and do the seal that way?

I'm tired of leaving spots on my driveway, my friends driveways, the parking lot at work, etc.

[Lscman]

90LSCdrvr,
The right time is when you rebuild the tranny. The easiest and proper way is to remove the tranny. that involves disconnecting the starter, driveshaft, shifter cable and torque converter bolts. The flexplate, which is basically the flywheel on an automatic must be removed and a special oil seal puller is used. Good Luck

[Guido]

mdcluth,
I agree synthetic oil will resist thermal breakdown better than any organic oil but what I'm talking about is the additive package. You say; "Time and temperatures use up the detergent, ash and other additives that give the oil it's ability to clean, cool, and lubricate.", and I agree, but these additives are not synthetic so they will break down just as fast whether in organic oil or 100% synthetic oil (actually they will last a little longer in synthetic oil because of the lower temperatures, but that's negligeble - not 5 times longer).

Also you said; "If you reduce the wear, you allow your oil to stay cleaner...", then is it safe to say that the benefits are not as great if the engine is already worn (100K + miles)? The wear is already there so there is nothing stopping the oil from getting dirty (blowby, etc.) so it has to be changed often anyway.

One last thing (hey, nothing personal), you don't mention the benefits of frequent oil analysis. Over-the-road diesel trucks can go 60-70K miles between oil changes but the sensible owners/fleets will do an oil analysis every 20K miles or so. I personally think 25K miles for a car is too long to check out what's happening inside the motor.

(I'm talking about fairly stock motors here - with high compression/turbo motors I would always use synthetic, but still change at 5K - it's cheap insurance for an expensive motor).

[Lscman]

There's nothing wrong with changing your oil often for extra insurance. I change my Mobil 1 every 25K miles, based upon lab testing I conducted and the results I witnessed. Most healthy, normally aspirated cars that do not see severe duty with good fuel management systems (EFI & no stuck injectors) can safely run 50K oil service intervals with filter changes every 25K. That's assuming clean road use and no dusty conditions. My engine shows almost zero cylinder wear (witnessed during head gasket change) and "like new" oil pressures at 225K+ miles.

[mdcluth]

Hey Guido, I think we're both on the same page on oil changes. I work at a large industrial engine company where we build and spec test engines used for natural gas compression, or power generation units. We use recycled organic SAE 40W engine oil. Every month, our oil is sampled and sent out for lab analysis looking for sodium and ash content, detergent structure, viscosity, debris and water in PPM (parts per million). We expect to see additives deplete naturally over a period of time, and water and debris will accumulate. This happens even faster on new engines due to debris left in oil passages as the engine gets flushed out on it's first run.
The reason we don't use synthetic oil is cost, but you also know that these engines are as dirty as they should ever be in their entire service right here at the initial run. The oil is centrifuged daily to remove dirt particles, and each engine's oil is drawn from the clean tank. Once the engine has been flushed, and initial break-in is done, we reccommend a lighter weight break-in oil to be used for the first thousand hours. Then the customer can use our reccommended run-in oil, or their own preferred type.
That's when the debate starts. Early in the engine's life is when you begin a pattern of proper maintenance that determines how long it will last, and how well it will perform. Your engine oil has a very critical function to perform in cleaning, cooling and lubricating precision parts.
Whether you use synthetic or organic oils, it helps to know what's going on in your engine. Oil contamination will naturally occurr from dirt particles getting in through air intake, metal from part wear, blow-by from both fuel and oil getting past the rings, and water from condensation or coolant leaks. Oil filters are designed to remove particles down to a certain micron size, but they don't remove water or fuel.
My point would be that you're right Guido. 25K miles is a long time to go without changing oil, synthetic or not. I will religiously change my engine oil every 3 - 5K miles, and I use organic 10W-30 oil. The biggest reason I do that is because I have always driven used cars, while my wife gets the new vehicle. I use synthetic oil in her car because I started maintenance from day one on that car. I will change her oil every 15K miles, but filters get changed every 5K miles.
You can't argue with results like LSCMAN is getting. If you can still see honing marks in your cylinder after 100K miles, you're doing something right, whether you use synthetic or organic oil.
One of the advantages of synthetic that my oil recycler tells me is that the additive molecules bond to the synthetic oil much better and longer than organic oil. Any oil type can become contaminated, and the only thing you count on to remove contamination is your filter.
This is why some people trust synthetics, and some don't. Is it cheap insurance to change your oil more often? You bet! But you have to make that call based on what works. Each engine will be a little different based on ring design, bearings, valves, seals, etc. This is why engine manufacturers reccommend different oils. The debate comes from using oils other than what the engine maker tells you to use.

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"Lincoln Moves Me"

[Lscman]

Great info. The reason I run synthetic is because the tests we ran at Chevron/Gulf Research & Development showed Mobil 1 provided better protection at 50K miles than fresh premium organic oil right out of the bottle. That result only applied street motors that were normally aspirated, "healthy" and the air was not laden with dirt. Excessive blowby and crankcase acid buildup on unhealthy motors drastically affects the results. Also, it is obvious I'm talking strictly gas-powered cars, not trucks, diesels or industrial/commercial apps. The used oils for wear comparison came from sedans on outdoor chassis simulators running severe duty taxi and police cycles. A more frequent interval for oil filter changing like you chose is wiser than my practice, IMHO...but I'm somewhat lazy and it's clear my motor is going to outlast the chassis. I've heard the filter bypass condition can occur well before the filter is full and this point is not published or consistent between brands. I've seen no hard data to support it, though. My oil filters don't have much "sediment" in them when I change them at 25K. I run a K&N air filter.

[Guido]

Thanks guys, excellent information - that's why this site is the best!
I have a few questions: what exactly is meant by "semi-synthetic"? Any comments about it?
If you're low on oil and running fully synthetic can you top it up with organic oil? How about if you're running semi?
Lscman do you add oil often between changes?
Any comments on installing remote dual filters? I heard it might create too much pressure for the pump, but it sure helps with cooling and extended filter changes.

One last question (while I'm at it) what do you guys recommend for transmission and differential?

Thanks again!

[Lscman]

>>semi-synthetic or synthetic blend is a marketing gimmick. Consumers absolutely demand it, so even Mobil has released one recently. They are about 20% synthetic and 80% organic but this ratio varies by type/brand. The organic components shear and break down just like regular oil which limits it's performance and longevity. It's analogous to taking four quarts of tap water and mixing it with one quart of distilled water. Whadayagot?
>>If you want to roll your own cheap synthetic blend, simply buy one quart of Mobil 1 for $4 and four quarts of Mobil organic for 80 cents each. You will achieve the same result. Yes, mixing is fine but serves no useful purpose.
>>Most Ford's use the huge FL-1A oil filter. It is absolutely huge compared to the filters GM runs even on their heavy duty big block 454 truck motors. It is total overkill. Oiling system failures often involve external oil line leaks due to perforation or other damage. They will probably decrease reliability for this reason.