Just wondering what you guys have found to be good oil change intervals when using full synthetic. I just did Mobil 1 5w30 on my Cobalt...

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Christian Thomas
87 Pontiac Fiero GT Burgandy/Silver 5.7L ZZ4 5spd
301rwhp/345rwtq

Next Mod: 88 suspension
06 Cobalt SS/SC w/ LSD

I change the Mobil 1 synthetic in our car every 5,000 miles. I figured that since I have the car jacked up to rotate the tires, it doesn't take that much extra work to change the oil as well.

The oil still looks pretty good after 5,000 miles, and can probably go much longer. I just figured that since I was getting dirty anyway... Not to mention, changing oil is a lot cheaper than changing engines.

I usually go between 7500-10,000 on mine. I do mostly all freeway driving. If I dont get those miles, I change it every spring anyway at the beginning of driving season. Ive done it that way for many years and never have had any oil related engine issues.

Its always best to go with your owner's manual if its under warranty. If not- 10,000 miles on Mobil 1 is generally no problem. Working on 15k in the Volvo with M1 now. I test the oil every 3k.

The owner's manual of my Jetta has 10k intervals listed in the manual even for mineral oil.

I use mobil one, and change the oil once a year.
If I go over 10K I change it sooner.

its kinda off topic but how do you like that cobalt, i just ordered one 06 SS1 (w/o supercharger ) saturday.

Some say every 5,000 miles but I feel safe that I will change about 3 to 4 thousands miles

You may feel safer but it's total overkill for regular oil much less a good full synthetic like Mobil 1. Interval depends on how it's driven, if your firing up a cold engine and beating the snot out of it for short distances, or just idling around town in stop and go traffic, change the Mobil one about 6K mile intervals, otherwise your safe to about 10K. To really be sure... get a oil sample kit and have it tested and find out.

Doesn't the Cobalt have an oil life indicator as part of the driver information control panel? I'd just follow that. In my Fiero I change the oil once a year, whether it needs it or not. I change the filters with K&N oil filters every 5-7000 miles.

Mobil 1 has a new one called Mobil Extend. They guarantee it for 15,000 miles or one year which ever comes first.Thats what I am using. Also it is a lot cheaper at Walmart rather than Auto Zone.
Don

i use mobil 1 extended performance, its rated for 15k miles, but i usually change it at 10k and it still looks good. 04 neon with 40k miles, been using full synthetic since the 2nd oil change. (6k miles)

I don't use a full synthetic in my daily drivers just because I can't get myself to wait that long to change oil. As you said, Scott, it's probably overkill, but I change the oil in my cars every 3,000 miles regardless. It costs about $12 for oil and $5 for a filter (max) which amounts to about 1/2 cent per mile in operating costs. Tires cost more than that per mile and fuel is 20 times that per mile at least. To me, an oil change is the cheapest thing I can do to a car and fresh oil never hurt anything.

I don't deny the value of synthetics in certain cases, but for a car that's well maintained I really don't see any cost effective benefit from it when you factor in the price of the oil if you're like me and just can't let your vehicles go that long without an oil change. If you can make yourself wait for 6,000 to 10,000 miles, then the synthetics become more cost effective, otherwise I don't see it.

John Stricker

quote Originally posted by Scott-Wa: You may feel safer but it's total overkill for regular oil much less a good full synthetic like Mobil 1. Interval depends on how it's driven, if your firing up a cold engine and beating the snot out of it for short distances, or just idling around town in stop and go traffic, change the Mobil one about 6K mile intervals, otherwise your safe to about 10K. To really be sure... get a oil sample kit and have it tested and find out.

Question: Is it fine to change to syntethic if you have small oil leaks? Does it remove carbon deposits thus it isn't safe to use if you have oil leaks. Clarify me on this.

I run Mobil 1 in my T-bird and Intrepid, and I shoot for a target of 3000 miles. 5 quarts for about $20 at Wally World. Overkill, for sure, but I waste a lot more money than that on other things. The extra ten bucks I spend on Mobil1 over fossil oil is peace of mind when I can't get to it on time for some reason, or I make a long road trip. I mainly use synthetic because of the cold flow characteristics.

I have used fossil Havoline in my Fiero since 1988, 10W-40 in summer, and 5W-30 in winter. Had the heads off last summer, and no ring ridge at all, no slime in the lifter valley or rocker areas. 184,000 miles.

Only 2 Ive had any direct contact with is Mobil 1 and Castrol. Ive seen engines that were borderline start leaking at mains when changing to Mobil. Ive not any leaks from Castrol, even changing over from regular oil at 70,000 on the vett.

If you use a turbo or supercharged engine, synthetic is highly recommended because it withstands heat that regular oil wont. All my cars Ive used it in showed at least a 10-15 pnd oil pressure increase when engine is up to temp.

quote Originally posted by jstricker: I don't use a full synthetic in my daily drivers just because I can't get myself to wait that long to change oil. As you said, Scott, it's probably overkill, but I change the oil in my cars every 3,000 miles regardless. It costs about $12 for oil and $5 for a filter (max) which amounts to about 1/2 cent per mile in operating costs. Tires cost more than that per mile and fuel is 20 times that per mile at least. To me, an oil change is the cheapest thing I can do to a car and fresh oil never hurt anything. I don't deny the value of synthetics in certain cases, but for a car that's well maintained I really don't see any cost effective benefit from it when you factor in the price of the oil if you're like me and just can't let your vehicles go that long without an oil change. If you can make yourself wait for 6,000 to 10,000 miles, then the synthetics become more cost effective, otherwise I don't see it. John Stricker

A man with a handwashing obsession could save a lot of money on soap if he just wore gloves. Obsessive-Compulsive Disorders don't really lend themselves to accurate feedback and rational behavior.

quote Originally posted by fierogtowner: Question: Is it fine to change to syntethic if you have small oil leaks? Does it remove carbon deposits thus it isn't safe to use if you have oil leaks. Clarify me on this.

I would NOT recommend changing to a synthetic lubricant if you are already experiencing oil leaks. Synthetic lubricants have a natural detergency that will result in the removal of build up around seals and such. This will most likely result in increased leakage on a vehicle that is already leaking.

Thanks FieroOilAnalyst. I won't change to syn.

Mobil 1 Synthetic for past 10 years in 3 different Fieros with 0 oil related problems. Oil & filter change every 6K miles. Would feel comfortable running to 9K. Have read a couple of tech articles stating full synthetics should have a 14K lifespan but I would not feel good about pushing that mileage range. For what it's worth.

Not recommended, but remembered this from wayyyyy back. My high school girlfriends dad had a 54 Ford at the time that he bought new. He put like 150,000 miles on it and had me take it in to work on it in our school auto shop. Oil was thick as syrup was the reason it was knocking and tapping. After questioning him about the problems, found out he NEVER changed the oil, only added to it when it got low. He figured as long as he was adding new oil all the time, it didnt need drained and changed.

quote Originally posted by ka4nkf: Mobil 1 has a new one called Mobil Extend. They guarantee it for 15,000 miles or one year which ever comes first.Thats what I am using. Also it is a lot cheaper at Walmart rather than Auto Zone. Don

Yea, I wouldnt trust it at that though. I ran that stuff in my DOHC, now as anyone with a DOHC knows, they have a built in oil life indicator. When the oil needs changed the lifters will tick after a hard run, I also notice the oil pressures running lower at any given tempature, change the oil and all goes back to normal. Last change of 15,000 oil, lasted 2000 miles. Granted I run it hard sometimes, and rev it pretty high, but still...

Plus keep in mind no matter what you use, keep the filter clean, when it gets gummy the pressure will rise, and the bypass valve in the block will open, allowing unfiltered oil to flow through the engine.

quote Originally posted by FieroOilAnalyst: Please change your filter more often than 15k.

I think the climate where you live has a big factor on your engine oil. Here in Florida I think you can go longer on a oil change than you can in the winter time in Mich. I say this because because oil gets polluted through condensation. That is why you see 18 wheelers leave their engine running when at a truck stop. But they do not leave it running in most of Florida or other warm states. In Hawaii the average temp is 72 year round, so the oil will stay cleaner there as opposed to Alaska. And In my Fiero sitting in the garage, It has zero miles on it since the last oil change in march. and I am not going to change that oil for some time as I do not believe the oil goes bad just sitting. The oil goes bad from starting and stopping. This 3000 mile oil change that the quick change artist come up with is a selling gimmick. My 2000 Mazda says in the book under my driving conditions to change the oil at 7500 and filter. So the best theory i suggest is to go by the recommended oil change the factory recommends.
Don

[This message has been edited by ka4nkf (edited 05-06-2006).]

I think you missed the very point of the post that you quoted. He said "Change your filter more often then..." and then you gave an argument about condensation polluting the oil. (I'm not really following that one too well, something about oil and water not mixing and seeing condensation boil off in exhaust as steam, but I'm a layman.) I'm not sure how oil will stay any cleaner at one ambient temperature (Hawaii) vs another (Alaska) isolated from any other factors such as use or load. I'd offer that there are many environments with delightful climate that have other horrible conditions on a vehicle such as airborne pollutants. While the oil conitinues to have a useful life while your oil filter is doing it's job, an oil filter is only going to take so much abuse. The oil filter is not a drain plug, it is quite easy to change an oil filter without draining the crank case of oil.

I learned early on that fresh oil is a pretty good performance 'mod'.

My dad had a 1960 Oldsmobile. 394 ci, and 320 hp. He didn't change the oil very often. I took the car out one day and it would only manage 95 mph. I brought it home and did an oil change. I took it out again and ran it right off the scale at over 120 mph.

That was my lesson.

Arn

about syn and oil leaks: syn will identify if you have a leak. when i bought my duke with 53k miles it didn't leak a drop of oil. one of the first things i did was change the oil and put in mobile 1 5w-30 syn. started an oil leak around the crank within a week. if i hadn't of spent so much on the oil i would have changed it out by now! next time i change it i'm going to use some of that high mileage dinosaur juice.

I agree with the oil Filter needs to be changed regular, Go into Walmart and look at the ice cream section and open the door for a few seconds and then shut. Then you will see the glass door fog up. this is what I call condensation and if you live in Mich. the same thing happens to you engine when you star it on a cold morning. The more starts and stops, the more condensation. This does not take place in warm climates. So my theory still stands that you change the oil and filter according to your weather climate. Take your auto tranny for example, you do not change the oil very often because it is more or less a sealed unit and does not take in air born particles or damp condensation.
Don

quote Originally posted by ka4nkf: I agree with the oil Filter needs to be changed regular, Go into Walmart and look at the ice cream section and open the door for a few seconds and then shut. Then you will see the glass door fog up. this is what I call condensation and if you live in Mich. the same thing happens to you engine when you star it on a cold morning. The more starts and stops, the more condensation. This does not take place in warm climates. So my theory still stands that you change the oil and filter according to your weather climate. Take your auto tranny for example, you do not change the oil very often because it is more or less a sealed unit and does not take in air born particles or damp condensation. Don

The filters used in automotive engines are not made with water removing capabilities. If they were, they would cost much more than what they do now. Any engine will create condensation after it is shut down. The small amount that is created will boil off once the engine comes back to operating temperature and is generally a non issue. This is why oil samples are to be pulled when the engine is at operating temperature.

Actually, the more starts and stops of the engine would create less of an opportunity for the condensation to build up than if you shut it down and let it cool all the way down.

Also, oil begins to degrade immediately. Oil does have a shelf life. Once you introduce new oil to an engine that has had old oil in it, you've just cut the shelf life in half. When you perform and oil change, up to 15% of the volume of the sump could remain behind if you do not do a thorough flush. This old oil can have a drastic adverse affect on the lifespan of the new oil.

While I applaud you for putting thought into this, the ambient temperature will play only a very small factor in the need to change the oil in an automobile. What's most important is that you are using the correct viscosity grade for the ambient temperature in your area.

Thanks- Matt

quote Originally posted by ka4nkf: I agree with the oil Filter needs to be changed regular, Go into Walmart and look at the ice cream section and open the door for a few seconds and then shut. Then you will see the glass door fog up. this is what I call condensation and if you live in Mich. the same thing happens to you engine when you star it on a cold morning.

Well, that's called condensation anywhere. Now take a blowtorch to that glass door and watch how quickly it dries up. Thats what happens when combustion occurs in the cylinder, and all that water that does not mix with oil blows through the exhaust. So... what's your point exactly?

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Telegram Sam. Your main man.

quote Originally posted by Telegram Sam: Well, that's called condensation anywhere. Now take a blowtorch to that glass door and watch how quickly it dries up. Thats what happens when combustion occurs in the cylinder, and all that water that does not mix with oil blows through the exhaust. So... what's your point exactly?

One thing is rust
I think a muffler and tail pipe (galvanized) will last longer in Hawaii than Mich. This is possible with engine parts.
Don

quote Originally posted by FieroOilAnalyst: The filters used in automotive engines are not made with water removing capabilities. If they were, they would cost much more than what they do now. Any engine will create condensation after it is shut down. The small amount that is created will boil off once the engine comes back to operating temperature and is generally a non issue. This is why oil samples are to be pulled when the engine is at operating temperature. Actually, the more starts and stops of the engine would create less of an opportunity for the condensation to build up than if you shut it down and let it cool all the way down. Also, oil begins to degrade immediately. Oil does have a shelf life. Once you introduce new oil to an engine that has had old oil in it, you've just cut the shelf life in half. When you perform and oil change, up to 15% of the volume of the sump could remain behind if you do not do a thorough flush. This old oil can have a drastic adverse affect on the lifespan of the new oil. While I applaud you for putting thought into this, the ambient temperature will play only a very small factor in the need to change the oil in an automobile. What's most important is that you are using the correct viscosity grade for the ambient temperature in your area. Thanks- Matt

Matt can you document any of the above, especially the shelf life of oil and old oil effecting the lifespan of new oil? What exactly would be effected in the new oil if it contacts a small amount of 'old' oil?

I thought I had a pretty good understanding of oil specifications, this is something I've never heard. Sounds like a sales pitch for oil flush equipment.

quote Originally posted by FieroOilAnalyst: Oil does have a shelf life. Thanks- Matt

Where is the date located on a bottle of oil. How do I know if I am getting Fresh Oil?
Don

quote Originally posted by Scott-Wa: Matt can you document any of the above, especially the shelf life of oil and old oil effecting the lifespan of new oil? What exactly would be effected in the new oil if it contacts a small amount of 'old' oil? I thought I had a pretty good understanding of oil specifications, this is something I've never heard. Sounds like a sales pitch for oil flush equipment.

Scott-

Don't worry about the sales pitch. I do not own or sell any type of flushing equipment. In fact, when I change the oil in my car, I change it like everyone else. I do a simple drain and fill. I don't subscribe to the Auto RX regime or anything of that nature. My opinion- engine flush = drain oil and replace filter, refill with new oil, run back to operating temperature, drain oil, refill with new oil. There are many out there that fully believe in the flushing fluids on the market. I am not dispelling any claims made by those companies or individuals but I'm also not supporting or selling their product.

New oil contacting old oil- Once an oil- or nearly anything for that matter- begins to degrade, the rate of degradation increases over time. Having said that- and some will think I'm going backwards here- when you change your oil at 3k miles, you are essentially taking good oil from your engine and adding good oil. Meaning, with today's oil, after 3k miles, chances are very strong that the oil in your engine is still in fine shape. Conversely, if you run your car for 25k miles on regular mineral oil, chances are extremely strong that the oil is severely degraded. While you'll be adding in all new oil, the residual old oil still on the mechanical components and the acidic sludge build up will have been severely degraded. This is when it is detrimental to the new oil. (I should have clarified this in the earlier post).

Regarding shelf life- You as the everyday car enthusiast or even repair shop will likely never have to worry about the oil on your shelf or the oil that you buy being bad due to shelf life. I bring this topic up only to indicate that oil does degrade even when just sitting in the engine albeit it takes quite a bit more time than when used in a daily driver. On a car that sits over the winter and is only used during nice summer days- the oil will still be fine. I apologize if my earlier comments led to a different conclusion.

This is more of an issue in industrial settings where new drums are ordered but the stock may not be rotated.

The oil degradation process begins almost immediately although extremely slow. The rate of degradation is increased when introduced to a contaminating environment. Being put into an engine is a contaminating environment (the metal is a catalyst for acid and oxidation formation). Being put into a daily driver engine is even more of a contaminating environment (add the heat and load for shear and further oxidation, additive degradation, possible fluid and environmental contamination). Being in an engine that is run hard is even more volatile (increased load, quicker shear, etc). Do you see how the harsher the environment the higher the rate of degradation?

If you find a quart of oil in a house that has been sitting for 30 years, chances of that oil being up to specifiication (obviously the specification applied when it was new) is slim. Furthermore, this oil would likely degrade at an alarming rate if put into a machine.

There is no arguing of anyone's point here. Dan is correct in the best bet is to follow the mfr recommendations on the lube change interval. Also note, the mfr makes these recommendations based on driving habits not on ambient temperature (that is really the point I was meaning to focus on). They may make different viscosity recommendations based on ambient temperature.

Let me know if I need to clarify. Sorry for the misleading post earlier.

That sounds good. One more question, does it take one sample kit for each oil test?
Don

quote Originally posted by FieroOilAnalyst: $35/ sample gives you: Wear metals Contaminant metals Additive metals FTIR- (oxidation, nitration) Base Number Viscosity Water % Fuel % I have sample kits here that I can send out.

quote Originally posted by ka4nkf: That sounds good. One more question, does it take one sample kit for each oil test? Don

I'd send you out a small sample bottle. That single sample bottle gives you all the tests mentioned above. (4oz sample)

Thanks for clarifying... It sounded like you were saying oil sitting in a sealed bottle was going to go rancid in a year or whatever. Average shelf life guarantee for motor oil is usually about 3 years. In a vehicle I like to see it changed about every 6 monthsto a year regardless of mileage if the vehicle mostly sits parked because of what you stated.

On the other hand... I can't see wasting fresh motor oil to flush an engine, sounds like an incredible waste of a hard to produce resource. Only time I've done that has been to flush out an engine where a blown head gasket caused the milkshake experience. Repair gasket, change oil, run it drain it and change oil again until clean. Or maybe on that vehicle where the owner went 96K miles on an oil change and what comes out looks like black toothpaste. That's when I have flushed in the past using a quart or two of transmission fluid along with 10/30 to top off and ran til hot unloaded and drained before doing a normal oil change.

I had a customer with an Isuzu Rodeo that got sludged up from extended oil change intervals where the TSB to run Mobil One 0w20 worked great. It stopped the lifter rattle in about 20 minutes and cleaned out the rings etc to the point where it burned about 2 quarts in 3000 miles with it smoking a bit, then it stopped using oil between changes entirely as the engine resealed with the parts instead of carbon. Only used the ultra light weight oil the one oil change, then used Mobil One 5w30 I believe an ended up switching to Castrol Syntec.