Use the exact weight that Honda recommends. The brand is your choice as all major brands are excellent lubricants. I personally use Pennzoil myself.
it's vtec not vtech... vtech is a cordless phone company... i have a 95 gsr and i use mobil 1 full synth...
No
use a 5W30 engine oil Brand is not important.
yes it will, but the 95 is obd1 and the 98 is obd2, if you switch the intake manifold and keep the obd2 sensors, you shouldn't get any codes assuming neither engine is vtec, if the 95 is vtec than you just wont use the vtec wires, if the 98 is vtec you will have to hook it up, but the engine will run fine even without the vtec hooked up.
SAE 5w30 any major brand.
you have many different options when it comes to this, you can go d15b7/d16 vtec head (this is a Frankenstein swap where you put a vtec head on a non vtec block), or d16 vtec, or single or dual cam Zc its personal preference, but do not go for the non vtec motors such as d15s and certain d16s research use wikipedia it works the best to find this information
Engine oil?? 5W30 synthetic is best.
The one the engine manufacturer recommends. The make is not that important, but the grade is.
Best is what the manufacturer recommends.
The best engine oils has a strong properties like Cools, Cleans, Lubricates, Seals, Cushions. And for new engine you can use Castrol GTX Engine Oil. Use exactly the weight of oil the manufacture of your vehicle recommends. All major brands are excellent lubricants so the choice is yours. Also use a quality filter and change it with each oil change.
Rotella 15w30 diesel engine oil
No you can not use gas engine oil in diesel engine oil because processing of diesel engine is different from gas engine oil. If you use this then it damage your vehicles.