Thread: synthetic vs mineral in the auto

i'm probably not going to be a huge help, but i use mineral oil in my auto trans. i do a 5L change every 5000kms, as i notice it does start to smell a bit burnt after a 1/2 days sand or mud driving. i'd suggest towing would be a similar stress. if the light has come on for you(i never have) it' definately worth, at the very least, letting a small amount into a glass jar and seeing it's colour and smell.

mineral is cheaper, and 100% fine/safe, but from my limited research, needs more frequent changing.

Adding to the complexities - I use semi synthetic - Penrite BMV developed for ZF and Merc transmissions. I'm not sure chemically what is so different about it, but it delivers much crisper power transfer than Transmax Z.

Its also 33% cheaper.

Originally Posted by edddo

... in the 98 disco 300tdi ... The trans temp light came on once for about a minute

There's a trans. temp. light on these things??? Huh?

While we are at it. My trans. oil level seems really high to me.

I dip the stick as per instructions and the fluid level has always been about half way up the stick. Way over the fill marks.

What would you do guy's. Drain/change and refill to the exact mark or leave well enough alone?

(Sorry Edddo, hope I haven't taken this thread off topic)

P.S. I use mineral ATF and synthetic engine oil.

discomuzz, are you checking when cold? i dont know what the process is for your exact car, but most owners manuals say to check when cold and in park. when its hot it will read higher on the dipstick(lucky you have a dipstick!!!) if its not showing signs of foaming and the trans feels consistent and somewhat smooth, i wouldnt think you have a problem.

Yep! I check it as per instructions. Cold at idle in park. Actually, cold or hot makes no difference.

Trans. seems smooth enough just worried about seals etc.

Originally Posted by discomuzz

Yep! I check it as per instructions. Cold at idle in park. Actually, cold or hot makes no difference.

Trans. seems smooth enough just worried about seals etc.

sounds like it is a bit over full then..I'd drain a bit off..or..is it due for new ATF if so then I would do it sooner rather than later.

yeah especially if its been over 30,000kms since the last change. if you tow reasonably often, or go off-road a bit, it's probably worth, at the very least to drop the pan/drain plug and refill with fresh oil every 5000-10000kms. i dont know if the internals of your auto are the same/similar to the D2, but i think the whole system holds about 9litres and draining from the pan removes just over 5litres.

That sounds a little full. To much oil can be as bad as not enough.

Synthetic vs mineral.
In the stock ZF Dextron 3 is fine and recommended.
If you have a heavily modded box then you need to run the right stuff.

My box has been built to use Transmax Z. I have to use it and it is very expensive. If I didn't require it I would run the cheaper Dextron 3 and just keep an eye on levels and condition.