OP here to report back on observations from more trips this summer.
I am now convinced that my truck doesn't like Shell gasoline. Shell gasoline just doesn't work very well in my 2004 Dodge Ram 2500 5.7L Hemi. I have tried Shell 87, 89 and 93 Octane and they all have the same problem when burning in my truck. There is a Shell station 1/4 mile from my house so that is the easiest place for me to fill up and is where I used to get most of my gas for the truck.
When I burn Shell gas (from maybe 4 different Shell stations in Maryland and New Jersey - including the one 1/4 mile from my home) my truck has the same problems. The problems include noticeably lower power when towing, running at higher RPMS when towing, exhaust smells like gasoline sometimes and the truck just seems to struggle more when towing. It is really weird that sometimes it seems like the gasoline is not burning all the way and I smell hot gasoline fumes in the exhaust.
When I use any other brand of 89 octane gas my truck runs smoother, gets more power at lower RPMs and the exhaust doesn't smell like gasoline.
From other reading on the internet it seems that the major differences between different gasoline brands are the additives and detergents that are added. My guess is whatever additives that Shell uses don't agree with something in my truck.
Again, my truck is a 2004 Dodge Ram 2500 5.7L Hemi. It has about 80K miles, is well maintained and passes Maryland emissions inspection. I bought it used in 2006 with 32K miles on it.
Ed
