Transmission fluid + engine oil question

I'm going to change filter and transmission fluid on my -97, it's overdue. I'm just going to drop the pan, no flushing. How much fluid is needed? I recall reading (probably in this forum but I can't find it anywhere) that by dropping the pan about 4 litres is needed to fill it up again but the local store says 5.7 liters.

Second question, when I changed engine oil last year I looked at Castrol recomendation table which said 5W-40 (the owners manual I had then is in Frensh, later I downloaded an English version). After doing the LIM gasket job recently I put in new 5W-40 oil (syntetic) which I'm now is about to change again to remove any remaining contamination.

I now discovered that Castrol had put up the european version of this model in their tables and there they say 5W-30 (or 0W-30) should be used. They still have 5W-40 if I look at the recomendation for the american model although it's the same engine. Looking at other oil brands availible here most recommend 5W-30 but in some tables it says 5W-40.

Looking in the owners manual (english) it says 5W-30 or 10W-30 and to not use any other viscosity.

I suppose I should put in the recommended 5W-30 instead of the 5W-40 I've been using, as I have to change the oil anyway. Comments?

I really doubt that it's going to make that much difference. I put 0W30 in ours a couple times when it was new, but then started using just regular ole 5W30. I think towards the end of our Venture's life with us I was running 10W30 because it had a lot of miles on it.

If you're in a cold climate, remember the thinner the easier it circulates when it's started.

The question was mainly on the viscosity when warm, 30 vs 40. I doubt it's a major difference but one should use the recommended viscosity unless having really good reasons to change AND know exactly what one is doing.. After some more investigation I believe the recommendation table that said 5W-40 is merly a typo as all other tables says 5W-30. I've used 5W-30 now when I did the oil change.