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I know GH recommends their hydro oil "only". Has anyone used say 5w-30 synthetic motor oil for an extended period? Or should I stay with GH's $$$$ oil?
If so, where is cheapest place to buy the GH oil? My local dealer wants $18.+ per quart.....

The MOBIL DTE 10 Excel 100 transmission fluid and the GH brand are both expensive.

Are there any other brands that are compatible? I tried Google to find a cross reference chart for the stuff but so far... nothing. If anyone has alternates I'd love to know. I have a local Tractor Supply less than 5mi away whereas the nearest GH dealer is almost an hour from me. Extra travel time and gas for round trip would make the tranny fluid even more outrageous. Other options would be a godsend.

TIA

Why are you replacing this oil?

Not replacing, adding to. Yesterday, in preparation for rolling my lawn, I checked the tranny fluid and the level is at the bottom of the two lines on the dipstick so it needs topping off. I did some further research on the Net last night and found the following...

Mobil DTE18M is compatible with Mobil DTE26

and...
AW68
Esso Nuto H68

According to the Grainger online catalog, WP143462 Premium Hydraulic Oil, 20 - Grainger Industrial Supply
DTE26 oil (available in 1 & 5 gallon sizes) is...
Hydraulic Oil (Premium) Heavy Medium
ISO viscosity: 68
SAE Grade: 20w
Viscosity Index: 98

(DTE24 is 10w, ISO viscosity 32; DTE25 is 15w, ISO viscosity 46)

FYI...

reynoldston said:

Why are you replacing this oil?

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Same as above. Not replacing, adding. I've had a very small leak in the system for years. VERY small. Now it's finally gotten to the add mark on the dipstick, (after owning this unit for 14 years w/500 hrs. I know, not many hours)

I know there's a couple other major mower brands that use Amsoil synthetic motor oil in their drive units. Not that I would use "motor oil" in the GH

About a yr & half ago, around here the dealer wanted $90-95 gal. iirc. I said ...""Uh...NO, ...that's crazy, I'll see if I can find a substitute".

That would be $180-190 fluid change!!! ...besides the motor oil & coolant. I know these mowers ain't cheap, & wiw to keep from having bigger, co$tlier repairs like a trans swap.

So, the MOBIL DTE 10 Excel 100 comes out to $5.28 per qt for me buying it by the 5 gal. bucket. I think I may have ~ 130 hrs on that last trans fluid change.

Me having a large yard, lot of trees & bushes, it takes a few hrs per mow. If I had a small yard & a small leak I'd be looking for some 1qt substitute too. :2cents:

I think I've decided to use this:

http://www.amsoil.com/lit/databulletins/g28.pdf

I get it for about $7.80 per qt.

I may have to fix that leak I mentioned as it's getting worse as time goes by. The fluid reservoir tank has a tiny crack in it. It's really messing up the rear lower area of the mower with residue

Could you just use a ISO68? My local Farm&Fleet has there brand for about $18 for 2 gallons. Thanks

ISO68... that's what I ended up using. Added many months ago and so far zero problems. If I had a brand new machine I might opt for the best of everything, but for a mower that's almost 20 years old I'm not going to spring for top dollar brands when my 721D gets along just fine with low cost alternatives.

Thanks, that what I was thinking too.

Where is the leak?

No leak, just wanting to change the oil and filters. To see if it will work a little better. The left drive seems weak.

bobojay said:

I know GH recommends their hydro oil "only". Has anyone used say 5w-30 synthetic motor oil for an extended period? Or should I stay with GH's $$$$ oil?
If so, where is cheapest place to buy the GH oil? My local dealer wants $18.+ per quart.....

Click to expand...

Here's some info I got from my neighbor that used to sell all of GH's oil to them (their factory is about 45 minutes from us):
A little history about oils with Moridge Mfg (Grasshopper Lawn Mower) in McPherson. When I was the Mobil Oil rep for the area, we supplied this plant with all of their hydraulic oil. It was Mobil 1 15W-50. I went to work for XXXXXXX Oil and got a call to come in and talk with one of the R&D engineers. He brought in some failed hydraulic orbital motors from their test stands. He and Parker (Mfr of hyd pumps and motors) said that the failures were due to the lack of anti-wear in our Mobil 1. They were not happy. What had happened is the EPA mandated a change to the levels of sulfur and zinc allowed in engine oils to reduce emissions. So Mobil Oil changed the formulation of their Mobil 1 to meet the EPA mandates and didn’t tell us on the industrial side of the business. Because Grasshopper was using Mobil 1 in an industrial type application, it was overlooked by Mobil Oil to let Grasshopper know. Mobil Oil and XXXXX Oil lost the business. Mobil 1 was the initial fill hydraulic oil for 20-30 years. However, it is not recommended by me to use Mobil 1 any longer, because there is not enough anti-wear in the new EPA approved Mobil 1 oil to protect the orbital motors in your mower. All of the blogs you see on-line are going off of old history that Mobil 1 is the best product to use, but they are not getting the protection they need. Also, I would not use anything but a synthetic oil, even though it is more expensive. Synthetics will give better wear protection also. So what I recommend is a synthetic oil, loaded with anti-wear additives. This RP product is what I would use and what I recommend. It will give you all of the protection you will need in any temperature. http://www.royalpurple.com/wp-content/uploads/2019/01/RP-PDS-Max-Cycle-2019.pdf

Can you point out the API Service Grade where this change occurred? The same thing happened to diesel motor oil when the API Service Grade went to CK-4; CK-4 oil has been found to not meet the specifications of previous Service Grade (CJ-4). Ford issued the following statement: https://www.fcsdchemicalsandlubricants.com/additionalinfo/Ford Motor Company CK-4 FA-4 Position Statement.pdf

Motor oil backward compatibility has always been a given, and even now, the fact that CK-4 oil is not backward to CJ-4 is not widely known. Thanks to ever-more restrictive EPA mandates, diesel motor oil API Service Grade is no longer a reliable indicator of whether an oil is suitable to use. That's why many oils now carry Manufacturer's Specifications listed on the container.

I may be wrong, but it sounds to me like the same thing has happened to gasoline engine oil. In the case of hydros using motor oil, it would be surprising to see a Parker spec listed on a bottle of motor oil.

This is one case where I'm glad a Lazarus thread was resurrected.

cpurvis said:

Can you point out the API Service Grade where this change occurred? The same thing happened to diesel motor oil when the API Service Grade went to CK-4; CK-4 oil has been found to not meet the specifications of previous Service Grade (CJ-4). Ford issued the following statement: https://www.fcsdchemicalsandlubricants.com/additionalinfo/Ford Motor Company CK-4 FA-4 Position Statement.pdf

Motor oil backward compatibility has always been a given, and even now, the fact that CK-4 oil is not backward to CJ-4 is not widely known. Thanks to ever-more restrictive EPA mandates, diesel motor oil API Service Grade is no longer a reliable indicator of whether an oil is suitable to use. That's why many oils now carry Manufacturer's Specifications listed on the container.

I may be wrong, but it sounds to me like the same thing has happened to gasoline engine oil. In the case of hydros using motor oil, it would be surprising to see a Parker spec listed on a bottle of motor oil.

This is one case where I'm glad a Lazarus thread was resurrected.

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I was thinking the same thing with the gasoline rated oil, around the API SN oils, Maybe that is why Hydro-gear has came out with their own oil.