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Synthetic Oils - Mileage Between Changes?



I have never run a full synthetic before,
but I think you guys have me convinced to start.

Previously, I have been using Syntec Blend, and change about every 4000 to 5000 miles, with about 80 to 90% highway driving.

I have heard conflicting arguements (imagine that :rolleyes:
about the life of synthetics.

HOW MANY MILES (in general) do you run a full synthetic before you do an oil change?

I am running the mobil one for 7500 miles as that is the longest allowable in the gm manual. It averages out to changing the oil about every 8 weeks, sometimes less.
3-4000 miles a month, just depends on the oilfield and how busy we are :B:
I used to use oil but now I use Syntec exclusively on my Avalanche Z-71.

I used to change every 3000 miles but now I let the on board computer tell me when it's time to change. The computer actually monitors the oils life. I noticed that I get more miles between drains on synthetic than regular oil.

Castrol Syntec is the best synthetic on the market from a 100 year old oil company . . . not a gas brand.

Lubricants are all they make and they do it the best for my money.
minutajj:First,the oil monitor does not "look at" the OIL in any way.It checks things like engine revs,temp,etc.It cannot discern between synthetics and 'standard" oils.

Castrol Syntec:This is the oil that crossed the line between synthetics as we used to know them,and today's "synths".It is an oil made mostly of Group 3,hydrocracked mineral oil(not a synthetic-it's dino).Check this thread http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=1;t=000042 Car and Driver exposed the Castrol mess years ago when Castrol went away from the PAO synthetic to a blend.
The current SL "dino" oils are very similar to Syntec in almost every parameter.If you really want to learn a lot aout oils go to www.bobistheoilguy.com and click on the "forums" section.These forums have several guys in the refining industry plus a knowledgeable regular core of posters.
Before synthetics, I'd always changed at 3-4 k miles. With synthetic in the Av now, I think that I'll give the oil change monitor a shot.
For warranty issues I would follow the manual.....no matter which oil you choose....

I for one now use the oil life moniter....and keep the receipts.....
I did my first change yesterday. The oil monitor went off at 4100 miles. Made the change to Mobile 1.
I am @ 8000 Kilometers and my change light still has not come on! How much more do I have to wait? I have done some towing and dusty driving and I am thinking I should just change the oil now!
Leather said:
I am @ 8000 Kilometers and my change light still has not come on! How much more do I have to wait? I have done some towing and dusty driving and I am thinking I should just change the oil now!

Isn't that 5000 miles for us non metric people? :)
4500-5k is my garage guys recommendation when running full syn.

As Ygmn pointed out, always save the paperwork/recepit on any oil changes in the event you do run into mechanical troubles and they come after you.

Leather, as i had posted earlier i am running 7500 miles on oil change since that is the longest my manual says i can go. This last oil change my light came on at roughly 7250 so i went ahead and changed it the next time i was in town.
This is almost all totally interstate driving with a little (little) in town mixed in. I do not know how far you can go without light coming on. My mechanic said he would start checking the computer each time i bring it in for oil change to see what the computer says (percentage wise). Give me something to go on.
I have not noticed any gas mileage fluctuation as i am getting near oil change time.
I have a general quesiton on motol oil changing.

From what I see on the boards, most people recomend changing at 3000 miles, or approx 4 times a year.

With my previous vehicles I have owned, I always went with 6000 miles or twice a year. Always with 'Dino' oil, and sometimes with additives (no more).

Of the '73 Doge Dart, '85 Tercell and '85 Silverado I have done this with (and over many, many years) I have never had engine problems. (yes, I might just be lucky ;))

On my AV, the GM oil life monitor recomends to change the oil every 12 months if the system does not activate, so they have gotten away from recomending just on mileage.

Is there anyone else out there who would regularly change their oil at 6000 miles?

I am not refering to heavy usage vehicles, only light usage.
As I am an A.S.E. Master Certified Auto Tech with over 25 years experience (no I am not tooting my horn) I change my oil every 3000 miles, also as far as synths use them if you want but I use a good quality motor oil and a GM filter. Cant go wrong this way and IMHO synths give prople a false sense of longer protection - as far as OCM (oil change moniters) I think they are glorified mileage counters as they cant tell you the actual condition of your oil.
My GM dealership offerred lifetime oilchanges(every 3000mi) for $169. Imagine, lifetime oilchange for that price. Course I have to purchase the filter which i only change every other time.

Works for me.
I have been changing the Mobil 1 every 7K miles on my '91 K2500 and plan to do the same on the Av. The K2500 has 114,000 miles on it and I add a quart about every 2000 miles which is good. I change the filter every time I change the oil. :B: If I had to change the oil every 3-4000 miles I don't think I would spring for the synthetic.
Ok... how many of you guys race the engine on your Av over 5000 rpms and run it there in a single gear??? Probably NONE OF YOU!! So the stats are and through personal experience, the only vehicles that TRULY benefit fron the synthetics are the multivalves high rpm revving sports cars or formula 1 or the off-roads that rev high and have a higher probability for thermal viscosity degeneration ...other then that simple oils and a little Prolong, Dura- lube or what ever...unless you are really lazy...synthetics...oil is oil...syns are syns...each has a place of there own. Forget about It.
In my 02 Avalanche I change the oil with Mobil 1 5w30 and a Hastings oil filter every 3,000 miles. I cut a few oil filters apart and the Hastings were the best made. Also the filter material seemed to be of a better quality.
In my opinion, Mobil 1 is the way to go. In the 90's a friend and I rebuilt the Quad 4 engine of an Olds Calis. At 201, 000 miles, parts were measured with a mic. They showed no wear. I was very impressed. Several months later when I bought my 91 Mustang, I used Mobil 1 even though the dealer said that it would void my warranty. Today at 96,000 miles, I runs as new. I also used Mobil 1 in my 96 Dodge Ram. Shortly before I traded it in I took it to AAA for a daignostic. All cylinders except one, were at 100% efficentcy. The cylinder that was not was at 95%. And the truck had 147,000 at the time. Mobil 1 is well worth the investment.
After my run-in time of changing dino to synthetic adding another quart every 3M (At 6M miles 5 quarts dino and 1 quart syn, at 9M, 4 qts. din, 2 qts syn, etc.) I plan to change syn at 5M intervals.
I have a questioin relating to synthetics. I just switched
to Mobil 1 at 9300 miles using the standard AC Delco
oil filter. Why do I have an increase in oil pressure?

I have seen other threads indicating the same, but no real explanation.

I registered my Avalanche with the chev owners center at www.chevrolet.com. It lists the maintenance recommendations for the Avalanche. If you put in your last oil change date and milage as a maintenance item, it calculates the suggested milage for the next change. I just performed an oil change at 4016 miles and the site lists 14016 as my next required change. It should be noted here that the 10,000 miles between changes is the maximum recommended by Chevrolet. No way am I going to run mine for 10,000 miles without changing the oil.

My read on the synthetic oil is that it is manufactured to retain its properties at a higher temp than regular oils. While few people are running their engines under extreem conditions, oil does break down at normal engine temps under normal driving conditions. The synthetics should break down at a slower rate than normal oils. That should allow the oil to remain in the engine for a longer period of time without causing any undue wear on the engine.

I have not used much of the synthetics in the past but I just put Mobil One in my Avalanche. If GM recommends up to 10,000 miles between oil changes using regular oil, I figure I'm save running the synthetic for 4,000 or 5000 miles between changes.

I have been using Amsoil (www.amsoil.com) for 21 years. My parents used it many years before that. Back then they had 25000 mile oil changes and change the filter every 12500 miles, or 6 months, whichever comes first. We usually always ended up with over 150,000 miles on our vehicles. We drove them till too many things started going wrong. Never did we have a problem with the engines or drivetrain.

Synthetics DO NOT break down. They get dirty. If you can remove the dirt, you can run the oil for hundreds of thousands of miles(people have done this). The amsoil filters are the best oil filters made, they filter out smaller particles of dirt than any others. Hastings filters are #2 for dirt removal. With Amsoils Oil Filtration Bypass system, you can run your oil for tens of thousands of miles. You just send in a sample of your oil every 3000 miles for analisis and you can tell before things start happening to your engine.

Also, if your running a true synthetic, you do not need to add additives to them.

The syntetics oils can have more dirt in them and continue to lubricate. That is the primary job of oil. Secondary is cooling. But, with the synthetics being able to keep lubricating longer with more dirt in the oil is where a lot of the extended oil changes come from.

With good filters, you can get this dirt out of the oil, and therefor cause less wear.

If you follow the oil manufactures reccomendations for changing the oil, you should be safe.

I have used Amsoil because it is the BEST oil out there.

I do know that running Amsoil at its recommended intervals will not void the warranty. If you get a Dealer that tries to tell you diffrently, just contact Amsoil and they will set them straight. There have been a few court cases in the past that also set presidence.

I know I will hear flak from this post, but, It would't be the first and it won't be the last.

Oh, and Amsoil also makes a 7500 mile oil that I beleive is a semi synthetic for those that don't want to think about going 35000 miles on a oil change.

I have not currently put it in my AV, but will as soon as I change the oil. I do have it in my Dodge Grand Caravan (124,000 miles on that) Engine, Tranny, Differential. The MPG on it increased about 20% when we did that. We run about 22 - 23 mpg avg now and were around 18 - 19 before. And I have it in my Corvette.

Most people would never try to run there oil for 35,000 miles because of uneducated and misinformation. I DO know that Amsoil used to have a guarantee that there oil would not cause your engine failure. Not sure if they still do though.

I have used amsoil for many years and many miles and have had no problems with it.

Oh, I also had an instance where my dad went about 75000 miles without an oil change on a Chevrolet Celebrity. as soon as I found that out I took the car and had the oil changed. It was the Blackest oil I have ever seen. it was nasty. But, we ended up putting another 75000 miles on it after that before we gave it to the Kidney foundation or something like that.

Amsoil doesn't just make oil either, they also have tons of other car care lubricants and cleaners.

I just ask you to go to there web site and take a look around.

There certainly is a lot of paranoia about oil change intervals floating around. I have a 03 Z66 Av that is about 4 months old. Dealer told me the oil monitor system is the key to a long good life of vehicle. I've got about 5900 miles on my Av, oil monitor is at 21%. I'll change oil soon. It just so happens I also have a 95 Chevy Tahoe 4wd with Louis area before moving south, and never an engine problem or failure. Did I change the oil every 3000 miles? No way. I used 10w30 quality oil. At first I was changing oil at 3500 miles like dealer recommended. However, this seemed absurd (and expensive) because I was changing oil every month and a half. I checked the manual and it indicates a light duty and heavy duty interval neither of which clearly applied to my use. It occured to me that with all the advances in oil (at least thats what they claim) and in engines why weren't the oil change intervals getting longer, not shorter? Some research and some discussions with actual knowledgeable mechanics led me to believe that changing oil every 3500 miles was great for the oil producers and the arabs but totally unnecessary under most driving conditions. After the initial warranty ran out, I started changing the oil in the Tahoe no less than 5000 nor more than 7500 miles (ie about every three months). As I said I've never had an engine problem and it still runs perfectly with normal maintenance at 159,000 miles. I might also add that recently we leased a 2003 Jaguar S Type R for my wife (i get todrive it occasionally). The Type Ris a high performance designation. It has a supercharged dual overhead cam V8 that puts out 396HP roughly the same amount of torque. It is high performance and it screams. AND the first oil change is at 10,000 miles and every 10,000 thereafter! Those are the recommended oil change intervals. Needless to say I asked the service manager about that and he said that is all that is required by Jaguar to maintain warranty. He suggested that if I wanted to change every 5000 for my own peace of mind, he wouldn't disagree, but wouldn't recommend spending the money to change any more frequently than that. So what's the deal with oil? The oil companies want to sell oil. The arabs want us oil dependent. The cars makers admit the rule of every 3500 miles is unnecessary except for the most extreme circumstances. Do what your comfortable with, but don't be a fool. Its your money.
I've owned vehicles now for over 25 years. Put over 100,000 miles on a 1980 Mitsubishi-built Dodge Challenger and a 1986 Pontiac 6000 STE that I purchased new. I've got over 200,000 miles on a 1989 Pontiac Grand Prix that I bought with about 13,000 miles. Never had any problems with these vehicles that were related to oil. A fellow who checked the compression of the Challenger's engine when it had about 120,000 miles on it was amazed at how high and consistent the readings were between cyclinders, even without know how long I went between oil changes. Used non-synthetic oil in all of these vehicles.

The best man in my wedding bought a new 1982 Toyota Corrolla when he got out of college. Didn't change the oil in it until it had 15,000 miles on it. He drove that car over 200,000 miles.

I agree with you Hunter2072 on not needing to change oil as often as some seem to like to do it. I've now got just over 20,000 miles on my AV and have changed oil twice. I figure going with the oil monitor or 10,000 miles, whichever comes first, along with the added security of using synthetic oil when I change, should offer me plenty of protection. The evidence above testifies to that.
Gentle-Men new to the club and guess i will add my 2 cents in. i am a Shell lubricant oil rep and i will not try and persuade you to use syn or not or tell you how many miles between changes as these all depend on wheather driving conditons and driving habits i will add that the people who beleive in addidng additives to the oil is doing a dis service to their engine. oil companys spend millions of dollars to create a formulation to work with todays engines by adding additives eg:slick 50 etc, you completely destroy the chemical make up of the oil use the reccomended viscosity and that is half the battle.