have read this site for long time and got a lot of usefull info.now I have specific question.a 1988 tcm 850 wheel loader. transmission is 4 speed powershift with torque converter.have always put utf in it.just got owners book, it says 10w engine oil for trans/converter.what should I run.the whole book seems old spec.engine oil says 10w winter,30w summer.i run 15/40.am thinking of change to 5/40 t6 or 10/30 t5 to help cold starting.would this be too thin for old sloppy engine in summer.trying to keep alive cause cant get parts,{any info on that},cant afford to replace.thank you for any info.

I think AW-46 hyd fluid is the way to go....

But, unfortunately... lots of folks just use "303" oil in most of the older ones.
"R & O" oil is one step better than "303".

R&O oil we used to get us by till our 55 gallon drums came in of Mobil oil for our large printing presses. The Chevron R&O had nothing for an add pack and was told by a large distributor that R&O oil doesn't have any AW/EP additive as a whole. We added some rotary screw air compressor oil that had a robust add pack to get some Phosphorus into the oil. When I see R&O oil I now see "no add pack" in my head and I want something on anything that moves. That is why I use Mobil oil for the presses, because they have something extra vs other brands in R&O esq oil class, where other don't. The hydraulic oil has AW in it where R&O would not.

I like the add pack in utf,thinking it might be better than hyd oil.or is it additive I don't need or want. 10w engine oil seems thin. I run chevron 1000 thf in other equip I own in transmissions.do you think that is any good for this.

I used to maintain some old Fiat equipment that called for 10w engine oil in the transmission, and all the lube companies I spoke to suggested UTF. I think UTF has a better add pack for the wet clutches.

Is the loader parked near power? If it is, an oil pan heater would allow you to use 15w-40 year-round and enjoy better cold starting.

What is "UTF?"

Sounds like a 10-30 Diesel oil would be best such as Mobil Delvac 10-30.

no power on jobsite.is 5-40 to thin.10-30 hdeo is good idea.should have stronger add pack.i think utf{universal tractor fluid} is 10-30.

5w-40 would be fine, and work year round.

ok.i will use 5w-40 in engine.then decide to use a good utf or 10w-30 hdeo in transmission.i don't know whats in these transmissions.never had one apart.are there clutches so the utf is better.or is hdeo stronger add pack and take heat better.