Yes you could put 33" tires on, you will have some clearance issues and gearing problems though. Take care of that and you could put on whatever size you want. You may also want to beef up your stock transfercase mounts or buy bigger badder ones..............
80w90 gear oil
Use exactly what is recommended on the label on the drivers door jamb and in the owners manual. Lowering the pressure to get a better ride is not recommended. You will effect the handling adversely on a vehicle that is already easy to turn over. You will also cause the tires to wear on the outside edges of the tires and will be buying tires much sooner. You bought a Samurai and you should have known it does not have a good ride. Sell it or live with the harsh ride.
SAE 10w30 conventional or synthetic.
GL-5 for gear oil and for engine oil use 10W-30
they will fit with wheel spacers. but how much articulation you will have might be limited. you want small enough tires that you have max flex when off roading. if you are just going to drive it on the street you will be ok. the truning radius will be affect too. They will most likely rub on the frame when you turn. 33 x12.5 are really big for the samurai. anouther problem you are going to have is you are not going to have enough power when running down the road.
GL4 any works. i use, Penzoil syncromesh in all mine... easy to find in brick stores.
you can also use a 1.6 with the adapters from calmini susuky swiff motor but you have to modify the firewall a bit as the distributer cap touches it
80W90 in both use lucas or some type of synthetic like redline.
Samurai used bows and arrows.
{| |- | The emperor was not a Samurai. But he was a swordsman. Many of the best samurai trained the emperor in the use of the sword. |}
The samurai took his sharp samurai sword and cut the watermelon in half.
A interesting detail about a samurai's training in archery is that a Samurai has to use his left hand to aim the arrow.