I was reading an early post and noticed that someone said to use 30W engine oil for the lower unit for a Volvo outdrive. My manual tells me to use gear oil rather than engine oil, of course my manual if for a 1992 290DP. Should i be using 30W engine oil or stick to the gear lube? "Volvo now recommends straight 30W, but any engine oil will work when it comes right down to it." or was this statement just for the 270 or 280?