My prior thread about a miss at idle resulted in no faults wre found.

There's a recent unrelated thread as well concerning mileage and premium to which I responded that in my '95 Passat (also recommended to run on premium), I saw virtually no difference in mileage. But that's a VW, and a different engine management system, maybe it doesn't matter on it, but does on the 850.

A post in the mileage thread stated that they had seen a 2 MPG difference in milage in their Volvo dependant on fuel type. A quick calculation shows that if regular gas resulted in 27 MPG and premium at 29 MPG and an 18.5 gallon tank, and assuming regular at $3.25/gallon and premium at $3.45/gallon (I know that price is 2 weeks old) that regular costs $0.120 per mile and premium results in $0.119 per mile...an almost negligable difference, if I get 2 more MPG.

But switching back to the rough idle thread, quite frankly I forgot that Volvo recommends premium and maybe the regular is causing some of my miss at idle, since nothing could be found wrong. So for the next 2 tanks, I'm going to run premium, check my mileage and also see if that rectifies my rough idle problem. I'll keep everyone posted on the results!

Ron