I'm not sure " ROBS POWER ... " is entirely accurate. Yes, the 5w30 will be thicker, but I'm not sure the average driver could really tell the difference. If you went from a 20 to a 50 grade, then maybe one could feel a bit of a difference. I have used 20w50 in a small, high revving 4 cylinder that spec'd 5w30. The car felt slightly more sluggish when cold, but on a hot day, at operating temperature, on the race track, I don't think there was very much difference. Maybe a couple of horsepower.
Originally Posted by bluesubie
A lot of European Subaru manuals that spec 0W-20 also allow ACEA A3 5W-30's. Your 86 manual doesn't make mention of this? The only 0W-20 that I would use in your conditions is something like Motul 300V. Otherwise, I would go with an ACEA 5W-30 even though it robs power.