Home | Mailing List | Specifications | Care and Feeding | Modifications | Vendors | Literature


Extended Oil Change Interval Tests with Mobil 1

New 4/18/06

For the last 106k I have been changing oil every 5k, with filter and the oil analysis came back "No corrective action required, oil is suitable for continued use. Resample at next regular Interval."

Since I moved I had only one analysis kit in my luggage, (used at 106.5k). It took longer than I hoped to find a new home, buy it fix it up and move in. I also knew I had been throwing out $30 worth of good oil every 5k every oil change.

I let this oil change go 9k and the results are the same: "No corrective action required, oil is suitable for continued use. Resample at next regular Interval."

Yes trace metals are higher than with a short interval but still OK, Yes the TBN is lower at 4.12 but still acceptable. Service was "normal" not severe including a few long highway trips and much house hunting.

I am not advocating extended interval with crappy oil, or even extended intervals for others even with Mobil 1. I just thought with the debate on if the new Mobil 1 is any good, I might just report my test results.

attachments - Oil analysis PDF
                      Nickel for bandwidth fund.


oil 115k.pdf    1,720k

oilanalysis 115k.pdf  340k

I ran Amsoil Series 2000 0-30 oil in my '89 for 25,000+ miles a couple of times when it was my daily driver. I had bypass filters and changed the spin-on filter at 10,000 miles or so and added new oil as needed, but never did the oil analysis say it needed changing even past 25,000 miles. And you have seen the pictures of the inside of my engine recently, it was like new. Bearing wear at 180,000+ miles was minimal as reported by Doug Lewis, perfectly acceptable to keep going, but we replaced them while there anyway.

Yea, most people throw away perfectly good oil by changing every 3000 to 5000 miles. Most new cars with oil change monitors will let you go 7000 to 10,000 miles. Some Porsche cars go much longer than that (they DO have bigger oil reserves on some of them though) and BMW also has oil change intervals much longer than typically thought. With a good filter and quality oil, especially synthetic, you can go 10,000 miles in most cars without any problem at all.

For those that will blast me for saying the above, remember, you are welcome to change oil as often as the environment and your pocketbook will allow. Is it "good insurance" as many will say? Probably, but you would need real good scientific instruments to prove that 3000 mile changes versus 10,000 mile changes (if done right, driving style makes a difference etc) made any difference in wear/tear. Of course I would not do this with anything other than an oil made for it, and that is Amsoil, and only Amsoil.

Don Mallinson

I've been running Valvoline 5W30 synthetic in my white (and now silver) 99 for the last year or so now. I switched to synthetic for the extended change interval that it affords me. I used to do the dino change every 3k or so. Now I do it at ~7k. Cost works out pretty close (I go to the local 10 minute quick change) and I don't have to visit him as often!

Dave Garber

I run 10,000 mile oil changes with my 4 cylinder turbo diesel EGR car. If that isn’t tough on oil then nothing is. I get it analyzed at 10,000 miles and it says ‘suitable for extended use’.

I run 15,000 miles on my BMW gas cars and get the same result. People that change their oil at 3,000 mile intervals are supporting terrorism (there, I stirred the pot).

By the way, I use Amsoil European Car Formula 5W-40 in all my cars.

Paul L Fisher

OK. This makes no sense. Tim sings the praise of Mobil 1 and no one jumps on him accusing of 'drinking Kool-Aid' or other stuff but us Amsoil users report similar stories and get slammed?

As for the Kool-Aid comment, Scott, aren't you the one who won't use anything other than Motorcrap ATF in your trans even though you have no tests or proof that switching brands causes problems?

At least Tim, Don and I have proof to back up our statements. I get every oil change drained out of any of my vehicles analyzed.

Getting back to Amsoil, so far the Amsoil haters have still only used the reason that it is an MLM to hate it. Get a clue, every product is sold by an MLM. When you buy Valvoline oil at Wal-Mart, Sheik Ahmed sells the crude to a broker who sells it to Valvoline who sells it to a distributor who sells it to Wal-Mart who sells it to you. Where is that different than Amsoil?

Paul L Fisher

I believe the reason no one jumped on Tim is because he didn't throw in a wildly provocative comment like, "Mobil 1, and ONLY Mobil 1, is made for extended drain intervals." In fact, the OP might be the least-biased thing I've ever heard from Tim! ;-)

Did you notice the part of Don's post that Scott quoted? Don left the door wide open with that one.


That is exactly why I responded...

Now to address the "motorcrap" ATF argument.

/begin rant

Our 99 has 125K on it's factory tranny, Many have not been that fortunate. It is due for another change, as it is starting to act a tad stupid (even more stupid than a properly operating AX4N I should mention) just like it did 35K ago, when fresh fluid cleared it right up before the trip to Indy.

ANY FLUID THAT MEETS MULTIPLE SPECS will have different anti-foaming agents and detergents in it than a fluid that meets a single spec. I DON'T CARE IF IT MIGHT LAST LONGER, BUT I WILL NOT CHANGE THE ACTIVE ADDITIVES IN A WORKING TRANNY THAT IS STUPID IMHO.

Actually I just came back from the Stealer yesterday. I ended up with 6 Gallons of Merc V and a Filter for ~$90.

Why am I so high on the "additive" horse? There is only one fluid I can run (and would run) in our simulator's hydraulic systems, and that is Mobile DTE24. That is the fluid the engineers designed the system to operate on, and I don't care if someone else comes up with a fluid that meets the same spec for half the price. To fill the system is about $1500 (200 Gallons). We do analysis on it quarterly and if it shows contamination or loss of additives it gets pumped out and refilled with new. Each motion system cost is roughly 1.5 Million (pumps, cylinders, and servo valves combined). So $100 in fluid for the ATX that motivates my car every 30K instead of *maybe* 60K on the Amsoil is a trickle in the bucket if it keeps me from that $2500 rebuild for even 20K whn you factor in the inconvenience of an unexpectedly broken ATX. I suppose if Amsoil would truly work for 60K then I am currently out the value of two flushes which is really only about $50 each. So monetarily I am possibly out $100 at this point, but the tranny is still alive. This is not saying that it would be dead if I had switched to Amsoil, but I am not throwing that variable into the ring at this time.

Now if I had one rebuilt with new seals and such and the re builder recommended a different fluid at that time, I would switch and stay switched.

/end rant


Ahhh... OK. Makes more sense. Don is wrong. Mobil 1 now does extended oil changes again. Amsoil was the 1st, Mobil 1 then followed on then dropped it. Now they are back.

Paul L Fisher

Way to go Paul! 

Don Mallinson


Truth is that ONLY Amsoil is formulated and advertised to go beyond 7000 or 10,000 miles. Get your own facts straight before putting people down. Nothing I said was wild, and only provocative to people that jump to uninformed conclusions. So there. :)

Don Mallinson


I think they "extended" their drain interval to 15,000 miles. Amsoil has been at 25,000 and beyond for decades. So my statement holds, nobody has longer recommended drain intervals, and it is backed by decades of testing, both in-house and independent.

Wonder who is going to be left standing tall now that the oil industry is admitting that Amsoil has been right all along, and that their oil is worth a premium due to the additive package, and that many manufacturers put synthetic in from the factory.

Come-on people, I am advocating a good product, and if you don't like it, then fine, but the facts are there.

Don Mallinson

Well, that's not exactly true. Mobile 1 sells oils that specifically state that they are good to 5000, 7500 and 15000 miles. Don't believe me? Check out the link below:


I personally don't care what anyone here uses, or who they are a cheerleader for. I've read enough about oil and have had enough discussions here and on other lists to know that ALL motor oils have great products and NONE of them are markedly better than the other.

Dave Garber

I don't know if I'll commit to extended drain. OK I saved a few bucks. But FE, PB, CU and SI were all way up, more than double on double the miles. TAN was acceptable but not optimal.

The few bucks I saved on an oil change would not buy a gasket set or set of bearings for the SHO engine. There is something reassuring, if extravagant and wasteful about draining good oil. I plan on keeping this car a long time and want to baby her.

- I have never found Don pushy or unethical RE: Amsoil; or anything else he sells.

- Scott is correct about changing ATF products without a rebuild, although it may be a distinction without a difference.

- I am not selling anything, just reporting in the test results, Nor do I think Don is particularly hucking Amsoil, he is just communicating his experience.

Sometimes I think this list is too quick with uncharitable remarks that do not move the dialogue forward nor add any light to the subject. We need to work on that.


Yea, I already noted the 15,000 mile interval, much less than the Amsoil recommended interval for the last couple dozen years.

Yea, there are lots of good oils, AND some bad ones, but nothing in my comment said any oil was bad, just that Amsoil had the longest extended recommended drain interval, the only one what was truly exceptional in fact. And that IS a fact. Nice that Mobil 1 is finally getting on the bandwagon.

As those that pay attention know, I have stated many times here that Mobil 1 is a very good oil. Amsoil's own engineers will tell you that if you call them up. It just isn't designed to do what Amsoil will do, and that was the point that you missed because you are so intent on trying to argue.

Don Mallinson

You guys that do go 15, 20, even 25K between oil changes, how often do you change your filter?


Again, to be fair your statement was "Truth is that ONLY Amsoil is formulated and advertised to go beyond 7000 or 10,000 miles."

Obviously, this is false (as in, your 'facts' weren't 100% correct here) and different from your current statement of "nobody has longer recommended drain intervals, and it is backed by decades of testing, both in-house and independent."

Other than that, as I said I don't care. I'm sure Amsoil is a good product. Nothing wrong with liking it and using it.

Dave Garber

OK - You Know What?

I Propose that we put a Surcharge of a Nickel on anyone who starts another "Oil" thread, like the 200K Attachment limit penalty.

HorsePiss oil from today is Better than All but the BEST Oils from even 20 yrs ago. Change your oil once in a while, ANY OIL, and You're Gold. Quit debating a spec FlySh!t on an Elephant - It's ALL Good, the differences are SOOOOO Small at this point.

Think of the Bandwidth Savings....

::Puts on the Flamesuit::


Yes, perhaps I shouldn't jump to conclusions. After all, up until a few moments ago, I respected your opinion...  - Dan

I'm not intent on arguing anything. And I wasn't commenting on the merits of Amsoil. I was simply pointing out that your comment was in error relative to other oils not having the 7500 mile and beyond recommended change interval.

Dave Garber

Go 25,000 miles no oil change with Amzoil and you'll void your new car warrantee in the (unlikely) event of an engine failure.

I use Amzoil but am not addicted to it. I also use Mobil 1 I also use SuperTec from Wal Mart

Used to use K-Mart oil back when they had their own house brand. Put 150,000 miles on my Datsun 260Z and the body was rusting away long before the engine was using any oil.

Mike Frey

Contact Information