Last week I did a road trip to pick up a"new" used passenger seat and rear seat for a 126 about 300 miles away in my 87 SDL. Drove there and almost halfway back when I decided to top off my tank at a "Pilot" off I95 near New Haven CT. I took on 10 gals. and added 7 oz of Power Service. The additive was a double dose as I've been using 7 oz too 20 gal. the last 6-7 tankfulls. Jumped back onto I95 and within a mile I could feel that something had happened. I lost about 15 MPH of the top end, 85MPH was the best I could do and it took some work to get there, cruise control had a damn hard time making or keeping 85MPH. I had just driven 425 miles immediately prior at mostly 85 MPH with plenty left to spare, actually did a high speed test at almost 110 MPH on I95 East in CT where there is a big long 2-3 mile downgrade into a valley! It seemed as if the engine was starved for fuel or air or both. It took me almost 5 days to burn up that tankfull and I didn't get the 30 MPG I had gotten the previous 6 tankfulls mileage actually dropped almost 2.5 MPG! Since then I've filled up at my usual pump and thing seem to be back to normal. It couldn't have been the addative as I've double dosed it before without a problem so it had to be the fuel!