PT Manual

[ldabe]

My manual is kind of weird.

Under the Service Instructions on page iv, says, Use only 5W30 motor oil in hydraulic tank.
Then two sentences down, to "change hydraulic oil & filter" it says, Use only 10W40 motor oil.

Well, which oil is it suppose to be?
What does your manual say?

 

[m5040]

It is weird. PT is a small company and appears not to have a proof reader. You could call Terry and ask him. IMHO, what do you use your tractor for and what time of year? If you mostly use it in the warmer weather, then go for the 10w-40. If you use it only to snow blow your driveway, use 5w-30. Do you keep it inside in a warmer garage for the winter months, then use 10w-40.

 

[MossRoad]

My 2001 model 425 said one thing in the manual and another on the label on the tank. I've been adding 5w50 mobile 1 at every filters change.

 

[ponytug]

Mine says 10w40 on the tank and in the booklet.
Here is how different weights and oils stack up;
(Vertical scales are logarithmic!)

Gear oils always throw me because the numbers don't correlate with engine oil.

(And we do it this way because? ...because oils didn't used to have any viscosity standards, so this is an improvement...., i.e. the same team that gave us pennies, shillings, pounds, guineas, drams, ounces and different pounds, and my all time favorites- barns, slugs, rods, and chains.)

Bonus points for standard setting: the W (for winter) oil rating is done at low temperature, but not always the same temperature. E.g. 5W has a cold cranking limit of -31F, but 10W the cold cranking limit is -22F...

All the best,

Peter

 

[ldabe]

You all are definitely smarter than me, that is nothing but confusing to me.

 

[ponytug]

You all are definitely smarter than me, that is nothing but confusing to me.

Sorry to be confusing. Not my intention.

Here is a graph of oil viscosities against temperature; (sorry it is in centigrade) the point being that as oils warm up toward operating temperatures (~100C) the viscosities get to be very close, so worrying about SAE 30 vs SAE40 weight oil isn't going to have much of a difference.

Top is 20W50
then 15W40
then 10W30
then 5W30

Big differences when cold, not so much when warm.

All the best,

Peter

 

[m5040]

So that chart indicates they all turn to water like consistency when hot. And if they end up being all the same when at operating tempreature, why not just use the 5w-30 and make it easier to start? I don't see any bennifit in having thick oil for that short period of time until it warms up.

 

[marrt]

I researched this issue a few years ago and made a post on here somewhere. The bottom line...you want a fluid that has low viscosity when cold, if you start the tractor in cold conditions, in order to avoid pump cavitation. Frankly, this is the most important consideration. Based on the specifications for the pump used in my generation 425 (max and min viscosity) a 0W-40 met the manufacturer's requirement.

As Peter's chart above shows, it's far better to "worry" about the viscosity at low temps than at high temps...in terms of saving your pump. A hot PT will be in the 80C range where there's not much relative difference in viscosity.

And, as a final note, if you really want the best fluid, and you're intend on using motor oil rather than a premium multi-viscosity hydraulic fluid (e.g, UTF), then you might look at an oil with increased anti-wear protection, heat protection, and foaming reduction. This type of oil is "banned" for vehicle use due to catalytic converter damage from the anti-wear additive and other reasons. Kohler offers this type of oil.

Here's a good video on the issue:

 

[ponytug]

Does anyone here use UTF, and if so, which one? Just curious.

BTW: having replaced the factory 10W40 with synthetic 5W50, I can't tell the difference when hot. Cold, yes, it cranks a little faster.

All the best,

Peter

 

[BobRip]

I am using 15w50 Mobil 1 in my 2000 PT 422. My garage rarely get below 60 F, so starting is not a problem. The PT does have more wheel motor torque when hot than the original 5w30. I think the 5w50 Mobil 1 would be a good choice. I may switch to that if I can get it easily.