Though there are various companies out there that sell good transmission fluid, the best is still directly from Honda. You can purchase genuine Honda transmission fluid from Honda dealerships or through online retailers.
Automatic transmission: either Honda ATF or Dexron III. If you have a Honda dealer nearby get the real stuff; it's no more expensive than a good auto parts store brand and Honda transmissions like it better.Manual transmission: either Honda MTL or Mobil 1 motor oil the same weight the engine uses.
Depends on if you have a manual or an automatic. Also depends if the car is under warranty, which shouldn't be an issue with a nine-year-old Accord. Manual transmission: The official recommendation is Honda manual transmission fluid. I used to use Mobil 1 5W30 motor oil with good results. It may be the same stuff. Absolutely DO NOT put 80W90 hypoid oil in it! Automatic transmission: Dexron fluid is okay if that's all you can get. Red Line and Amsoil also make good compatible transmission fluids...but I would use Honda Genuine fluid in it. If the car is under warranty: Honda Genuine fluid. Honda is REAL nit picky about you using their magic juice when your car is under warranty; if they have to do warranty service they will sample your fluid and, if it's not official fluid, deny coverage because "the fluid caused the failure." Which is baloney in most cases, but it's best not to provoke them.
Do not install any Super Tech or Fram filter on your Accord. Purchase a quality Purolator, Bosch, Mobil 1, or Honda filter.
You must use AFT-Z1. The part number is CA66689. If you use Dexron III a friction modifier additive must be used with it such as Lubeguard or Kleenflo Platinum. This will help change the chemical nature of the Dex III so that it acts like Z1. Dex III by itself will cause damage to the transmission in a 1999 Honda accord. Honda used Dex III in transmissions built up to 1995, but after that they redesigned the transmissions and switched to their own fluid so be careful.
It would be Toyota type IV or WS fluid. Recommend you purchase from the Toyota dealer. The Toyota dealership parts store can tell you which one is for your model / powertrain. Type IV transmission fluid (possibly Mobil 3309 ATF) Mobil 3309 meets Type IV requirements. Not sure which company and type the WS ATF is. I would assume Mobil Oil as well, but is a different transmission fluid from Type IV.
5W20. I would choose a good-quality synthetic - Mobil 1, probably.
The alternative to Hyundai diamond spIII auto transmission fluid are : AUTOMATE TRANSMISSIONS FLUIDS Mobil Multi-Vehicle ATF Mobil 1 Synthetic ATF SHELL DONAX* TG AUTOMATIC TRANSMISSION FLUID https://www.mobiloil.com/USA-English/MotorOil/Other_Products/Mobil_1_Synthetic_ATF.aspx
The dealer says to use only 10W30 motor oil I'm surprised a dealer would say that; even though it's a good answer. Honda MTL, which is their Manual Transmission Lubricant, is sold at Honda dealers and is recommended by the Honda literature. I recommend Mobil 1, same weight as you've got in the engine. Usually 5W30 or 10W30.
semi sythetic Esso /Mobil Lt 71141
Whichever one is sold at the station with the best Coca-Cola prices. Both of them are quality fuels.
Mobil 1 Synthetic ATF is supposed to be really good.