I have made runs previously to the big city, 190 miles round trip, with no increase in mileage. Those were all highway miles too. The main difference between the last interstate hop and the mountain trip was the change in plugs. I got rid of the plats and put in copper cores. Could be the combination of plug change and blowing out the crud was the key. What ever the case, I'm not complaining. We'll see what the next tank does.
73 280 SEL 4.5