NorthernSands

Just for future reference, the rough idle could be the normal recalibration routine that these DERVs do every so often. I was concerned when mine started it doing it, but a Subaru mechanic mentioned the recalibration. Next time it happened I left it alone for a few minutes and it smoothed out to better than it was before. Of course, it might not have been that...

When I first picked up my '09 Diesel Outback back in October I used BP Ultimate. After about a month I switched to Shell Nitro+. I'm not sure I gave the BP stuff enough time to notice a difference (only 2 or 3 tanks). I switched because of the alleged increased lubricity from Shell (Source: HonestJohn). Using the Shell stuff the smoothness, smokiness and pokiness have all been gradually improving. It recently went to a Subaru main dealer for a service and the mechanic said it was the smoothest one he's heard running. It was when the car was being serviced that the mechanic asked, when I told him what I ran it on, if it ever runs lumpy at idle. I said it did and he advised me that it was the ECU recalibrating the injection timing and I should leave it to it. Sure enough, next time it happened I left it running for a minute or so and then it smoothed out. It's been even better since then. I have not, however, ever filled it on standard diesel, so I can't make comparisons really. It may have improved in the way it has even if it was on normal fuel. Maybe it was just in a poor way when I bought it. I have used BP Ultimate in my '01 Defender TD5. Although she ran markedly better on it, it's an unfair comparison because before that she only ran on the crappy diesel that's available in the Middle East.