AUTO SERVICE...........old oil with new?

wagonmaster

wagonmaster

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While discussion are on about fresh fuel mixing with old fuel i did a auto oil service and filter change on our small auto hatch a few days ago, total oil capacity is 5.6 lts. I didn’t think much about auto oil changes until 12 years ago as we did not keep our cars long enough to change the automatic oil twice.

If i just changed the automatic oil via drain plug and fitted new filter etc i would only have change 2.1 lts of the total oil capacity of 5.6 lts.

Doesn’t sound like a big deal, but changing the tranmission oil this way draining and refilling using just the 2.1 lts can be a problem long term. This 2.1 litres of new oil will be mixed with 3.5 litres of old oil, so the new oil (that is 100% of the 2.1 lts of fresh oil) will become 62.5 % fresh oil after first drain, 39 % after 2nd drain, 24 % after 3rd drain and after 4th drain my fresh content of oil in box would be only 15% new oil (and 85% old) these are aprox figures.

The best way to change all the oil (98% anyway) is to disconnect the return hose line running from cooler in radiator back to the transmission you can fully flush the transmission for a complete fluid change using fresh oil, if this line is flexible disconnect at tranny, if not disconnect at radiator end. Place a hose over this into a large container and get someone to add oil at filler hole as it is pumped out(place transmission in drive and leave idle) hopefully this will work.

I know another way which is the 10/10/10/10 method, which involves driving 10 klms then change oil, refill then drive another 10 klms and so on and so forth till you do the forth change, this will give you an end result of 89% fresh oil, but you would go thru 8.4 lts of auto fluid to do it?

If you go to an automatic transmission shop they will just do the standard auto service/filter etc, if you want it all changed they will do a full flush similar to above, but you will be charged an additional $80-$100 for the oil/work performed.

For preventative maintenance reasons a good additive works well between changes.
 
Fresh ATF replacing 2.1L out of 5.6L is 37.5% fresh not 62.5%.

And yes the best way is to flush it as you mentioned until clean oil comes out which in my case took 12L of ATF
 
I can see how you got the 37.5% total volume using the 2.1lts x 100 divide by 5.6 total volume, i used a different calculations i got from another oil testing site, it gave me the breakdown of only the added 2.1lts of oil (in percentage) reducing composition over a period between oil changes, which it worked out that the 2.1lts to break down to 62.5% at the end of that period, thats aprox.(dont ask me how they worked it out, thats what it came up with) ? I could have done it your way and not over complicate things i guess or just left it out altogether, putting calculations aside altogether, you get the general idea of how it breaks down over time mixing with the old oil each time you change it
So obviously its best to change all your oil (flush) first or at the latest 2nd change.

I see some auto boxes now are sealed for life (no dipstick) so you can't check it or change it. The manufactures are now realizing that sealed for life (100,000+ klms) isn't such a good idea as the oil breaks down over time/and usage (lite or heavy) and klms affect it as well...... Gee who would think that?

Some of the boxes do have a filler bolt hidden down the side of the box along with a check level bolt (in some US models i have seen) but no dipstick, so with some of these sealed for life boxes you could do an oil change, with a bit of mucking around, not sure if the aussie boxes are in this category or not.
 
TBH I feel those sealed for life transmissions are a con to get fleets to buy cars because for them servicing costs are really important.

I know that Mercedes put out a note that sealed for life transmissions should still be serviced (obviously once the cars were no longer new).

With newer synthetic oils they can obviously cope with extended intervals but for the lifetime of a car it is just too long (potentially).
 
wagonmaster said:
If you go to an automatic transmission shop they will just do the standard auto service/filter etc, if you want it all changed they will do a full flush similar to above, but you will be charged an additional $80-$100 for the oil/work performed.
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The transmission shop I use recommended to me just doing a more frequent fluid and filter change rather than a full flush (I think a fluid & filter change gets out about 50% of the fluid on the ZF though as they have a beefy sump), but I suspect part of this was because the ZF Lifeguard ATF for the ZF 6 speeder in the Falcons is a damn pricey ATF.

Ford say the transmission is sealed for life (*cough* bullshit! *couch*), ZF on the other hand say it is good for 100k between services. The transmission shop recommended doing the filter and fluid at every 45k to 60k, so I personally think that's good enough as it should over time maintain a decent enough quality in the oil.

Another very different example is my old man bought a VX2 Commodore that had done 160k and eventually sold it with something like 320k on the clock. In that time I don't believe it ever had a transmission service, only a couple coolant changes (and these were only because parts in the cooling system failed from age) and again only a couple brake fluid changes (only done because I was changing brake pads and rotors for him). It did start burning a little bit of oil between oil changes (some of which I think were blowing out to 15k to 20k intervals) so he would top it up with the old used oil from my cars (I stockpile used oil for a bit before doing a tip run to get rid of it). In his case his lack of servicing caused no real harm to the car and had no impact on the minimal amount he ended up selling it for...

So getting back to the original topic of discussion, I say do a 10/10 or 10/10/10 fluid change using a quality ATF and then just do a fluid and filter change at say every 30k or 40k.


Spetz said:
TBH I feel those sealed for life transmissions are a con to get fleets to buy cars because for them servicing costs are really important.
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Yes I agree 100%, however, it's not only directed at fleet buyers. Private buyers also can be guided by cost of ownership when determining which new car to buy, especially these days when manufacturers are trying to compete by offering the lowest capped price servicing.

Isuzu for example used to do 10k/6 months service intervals for the D-Max but for the 2017 model they extended these service intervals out to 10k/12 months and dropped the capped price servicing. Now you get the car reviewers writing in the comparison reviews about how it is one of the cheapest utes to service.

However, if you look at what their service schedule actually covers, they only change the oil every 20k. So now you have gone from having your oil changed every 12 months (during which most people probably don't do 20k), to people actually doing 20k on a crappy oil that the dealer bulk buys (plus if they do alot of shorter trips you will have way more contaminants and diesel dilution after 24 months).

Will the engine outlast the 5 year warranty? Sure it will. Will the engine still last as long after that? Probably not. Will the engine still outlast the rest of the vehicle's components? Who knows.
 
The servicing interval change may have been due to a swap of oil the dealerships use?
20k km on high end oil in a modern engine with precise tolerances seems reasonable.

But yes I agree, people have this (understandable) stigma that they will be going into the dealership and charged hundreds of dollars every few months which they now think will be free but in reality they are getting $100 worth of value per year.
 
Spetz said:
The servicing interval change may have been due to a swap of oil the dealerships use?
20k km on high end oil in a modern engine with precise tolerances seems reasonable.
Click to expand...

Good point, they did get a DPF added in now, so they will need a low SAPS oil that most blenders will probably use a synthetic oil to meet. However, I'd be very curious to know if the dealers actually start stocking and using it, especially given that the cost of the services have been reduced...

Personally though I still think the interval changes are more about appealing to fleet buyers (from what I understand Isuzu wants to push harder into the 4x2 ute market) and also private buyers that are influenced by servicing costs.
 
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