I have a 98 S90 with 170k miles that I bought with 100k. Just resently I experienced a Head Gasket leak and due to the cost of various repair options, it was recommneded that I replace the engine with another 98 S90 engine with 80k (not sure this was a wise choise, but it is in the past). After this engine replacement, I have taken a interest in making this engine and car last forever (give or take a year or two). I have changed the engine oil to a synthetic blend and with the next oil change will be going to 100% systhetic. The other fluids are a bit more questionable. For the tranny, several opinions are out there, from only use Dexron III or Mercon to go to synthetic for everything. The other fluids (power stering, break, rear differential) also are in question. Please help, I am fairly mechanically incline but have not ussually taken an active part in maintaining my S90 other htan to take it to someone to do the work for me, I would like to both start working on my S90 and make it last a long time. Thank you