Thread: Oil Recommendation for LT95 4 speed box and Isuzu 4bd1

Sooo, (he wrote, digging up an old thread instead of starting a new one), way up here where it's hard to get things I could run in a brand-new LT95 on whatever 20w-50 the Shell or BP roadhouses sell and then change to HPR30, which is easy to get - if I can't find an MTF as recommended?

Yep, if using an engine oil just change it frequently, eg. When you do your engine oil.

Indeed, that was the plan. I can get a drum of engine oil pretty easily, (there's a guy in Perth on eBay who dropships Penrite), while on the other hand ordering anything odd can be a teeth-pulling exercise that may take weeks . . . or months. And it doesn't help when the local Shell mysteriously dropped all greases and gear oils last year.

I love a good thread bump!

Deciding what to lube my new Isuzu + LT85 + LT230 with and thought I'd see if anyone had any objections before I spend all my money on oil! I've stuck to everything Penrite in my Disco for no special reason....and that's now what's in the shed. Happy to branch out.

Isuzu engine:
Penrite HPR Diesel 20W-60. Although is around $85 for 10L. Should I ditch the Penrite and go a cheapie?

LT85:
Castrol Syntrans 75W-85 or Syntrax 75W-90. Rick speaks too highly of it for me not to try it.

LT230:
In my Disco LT230 I've been using Penrite GEAR OIL 85W-140 Mineral. (Use to be called Hypoid 85W-140). I've only just realised this is mineral based and higher viscosity than some are mentioning here. Should I keep running this in both LT230 and my axle diffs, or go to a syn in lower viscosity?

Originally Posted by Judo

Isuzu engine:
Penrite HPR Diesel 20W-60. Although is around $85 for 10L. Should I ditch the Penrite and go a cheapie?

From my research the Isuzu doesn't really require anything fancy as far as oils go. Anything from the majors would be a safe bet, I use Castrol. What does benefit the Isuzu is the filter setup, look towards getting the dual oil filters if you don't have them already.

Originally Posted by Judo

LT85:
Castrol Syntrans 75W-85 or Syntrax 75W-90. Rick speaks too highly of it for me not to try it.

I'm not sure it matters, it seems the LT85 is weak behind the Isuzu so the hammering it will get behind the engine negates the needs for a specific oil. LT95 is proven behind these engines and is a good option.

I realise I will need a long term plan regarding the gearbox, but I'm hoping I can make the LT85 last a while at least. I'm not sure I subscribe to the idea of "giving up hope" for it and just using any oil. As I understand it the LT85 and LT95 are similar in terms of oil requirements anyway, so whatever I decide is good now may help later if I swap to a LT95 as well.

Originally Posted by Judo

I love a good thread bump!

Deciding what to lube my new Isuzu + LT85 + LT230 with and thought I'd see if anyone had any objections before I spend all my money on oil! I've stuck to everything Penrite in my Disco for no special reason....and that's now what's in the shed. Happy to branch out.

Isuzu engine:
Penrite HPR Diesel 20W-60. Although is around $85 for 10L. Should I ditch the Penrite and go a cheapie?

LT85:
Castrol Syntrans 75W-85 or Syntrax 75W-90. Rick speaks too highly of it for me not to try it.

LT230:
In my Disco LT230 I've been using Penrite GEAR OIL 85W-140 Mineral. (Use to be called Hypoid 85W-140). I've only just realised this is mineral based and higher viscosity than some are mentioning here. Should I keep running this in both LT230 and my axle diffs, or go to a syn in lower viscosity?

10W-60 is miles too heavy in the Isuzu.

A good 10/15W-40 is more than enough, I don't care what brand as long as it's at least a CI-4+/ACEA E4/E6 oil it will protect properly.

If you want to go all out you can get full syn 10W-40 HD diesel oils for around $165/20l retail which IMO is good value.
ATM I'm using Penrite Enviro Plus 10W-40 (Formerly Diesel SP) in the Nissan TD42T, an oil blended for Euro and Japanese HD diesels.
I haven't had to adjust the tappets in several hundred thousand km.

LT95, either of the Castrols would be good, or if you're feeling flush consider Motul Gear 300.
At 0*C it's thinner than Syntrans, yet the same viscosity as Syntrax @ 100*C and yet it doesn't shear and it shifts really well. Very exxy but a brilliant manual trans fluid.


With the t/case and diffs, your call.
I don't have a problem with a 85W-140, I've been using a syn 80W-140 for years in the Sals and LT230, I just use a syn 75W-90 in the front diff (Syntrax) as it's what I use in the Patrol g/box.
You will need to take a little longer with your warmup with an 85W-x, it'll take a couple of more km to get thin enough to get everywhere properly in a compartment on a cold morning.

As always Rick, you've qualified your answer beautifully and given me some great feedback! Thanks.

10/15W-40 engine oil it is.
Motul Gear 300 look a bit too "premium" for my liking! Will go one of the Castrol SyntraX's for the main gearbox.
I'll use up the rest of my 85W-140 on diffs and transfer case, then consider moving to thinner syn.

Cheers.