Joseph,

Both are actually easy. Its the results that are unknown over time since the powertrain was not developed as a system to have modifications outside of the original intent. Also the days of an ePROM (actual chip) are gone. Today the calibrations are typically flashing into ROM.

Jim

All great advise, that was first time I put premium fuel in maybe I get better mpg with regular well see this next trip.

Might be the difference in a 6 speed and 8 speed that I have

Dennis66 Dennis,

I found this in the owners manual where FCA recommends 87 regular to 89 mid-grade fuel.

"This engines is designed to meet all
emissions regulations and provide satisfactory
fuel economy and performance
when using high quality unleaded gasoline
having a posted octane number
range of 87 to 89 as specified by the
(R+M)/2 method. The use of 89 octane
“Plus” gasoline is recommended for optimum performance
and fuel economy"

This is done to account for variation in knock sensors, compression ratio variation and so on. It would be good for non-towing to test the fuel economy between 87 and 89 octane fuel to see which will provide the highest fuel economy. Or which fuel will save you money based on cost/mile. The drive cycle and weather should be as consistent as possible for a representative test.
Light spark knock is fine but heavy knock should be avoided. If your experiencing any heavy knock events, 89 would be the best overall choice. Running premium fuel (90-93 based on region) will most likely lower fuel economy due to a slower burn rate due to a calibration that does not account for the increased octane over 89.

For towing, it would be best to burn 89 octane where again, the additional octane will only cost more money and provide no real benefit. This is of coarse that the calibration and hardware variation was accounted for during a heavy tow.

So you know I'm not blowing smoke...I started my career at Chrysler and was responsible for performing base engine calibration (including knock control) in what I consider the be the best dyno facility on the planet located in Auburn Hills, MI. Being a GM guy, I finally ended up at GM's Milford Proving Grounds to calibrate all their Gen4 and early GenV performance engines. What I learned in doing this work was to keep your factory engineered vehicle exactly as it left the plant, including filters. I've seen engines destroyed in the field due to defective aftermarket oil filters as an example. I was amazed early on to learn what goes into something as simple as filters so be sure to use Mopar filters and Ford guys Motorcraft, GM....AC Delco. It really makes a difference. I've built race engines years ago and while they were extremely fun, they did not last as long as they did in their original intended design since the stresses of higher compression, airflow and resultant torque will eventually take its toll on the powertrain.

So ultimately the choice is up to the owner in how they treat their vehicles and only want to share what I've learned of the consequences in modifying a factory vehicle built for reliable operation.

Jim

My background is similar to Guest Jim's. There was a time when Canadian emission standards were different than US and I worked for GM Canada, but the dyno and road test work were done primarily at the Milford Proving Ground. I then branched into propane and CNG fuelled vehicles which GM Canada had a lead role on, but most testing was still done at MPG. Ironically, Jim & I were working at the same facility at about the same time, but never crossed paths. (it is a BIG place!). It took Grand Design RV ownership for us to finally meet.

Rob

Hey Jim, I worked at GM engineering center on Mound spent lots of time out at Milford. I was a chassis engineer from there I went to work at Deere here in Moline and built there main testing facility. I to lived on dynos as I has a big drag racer in the day, with all the new stuff its now the young guys game. I actually had a 70 real Hemi cuda I raced in the 70's

I worked at GM for 14 years starting in 1977, and just retired from Deere year ago Jan

Cate&Rob Rob, It is a special place and I'm glad that I've met you here and to have this common background. I miss it there, but I've already adapted to retirement. You mentioned I would be busy where right now we are re-locating to Ohio so I can help my parents out more often, and man are we busy.

Dennis66 We crossed paths with the SB Car chassis guys back when we were crushing records on the Nurburgring. I would tune cals for production to eek out every single newton meter of torque to accomplish those goals. And we ran the heck out of them where most of my work at MPG was in the cars. I'm in performance withdrawal today even though my exposure to those cars were not every day as it was back then. Last car I worked with and driving between MI and OH was a beautiful maroon C8. What a machine!

I've been to JD. If I remember correctly they had a unique angle in looking at the engine in the test cell at 45 deg or so. Do I have this correct?

Jim

Im sure you do up in Waterloo is where most of engine testing is done. They also have a facility in Torreon MX I have been to, to often. All the dyno cells in Waterloo are now generative and produce enough electricity for most of the lab.
I lived in Lake Orion when I worked at GM I was born and raised there till I left during the auto crash and went to Deere. Like you Im now retired and love it. We do have a travel plan for 3.5 weeks going up through Wisconsin through uper and down near Petoskey and down back home in Iowa. I have camped at so many places in Mich. Im hoping this trip will give me better mpg as its mostly flat. I guess if I was that concerned I should of bought a diesel. I think my Ram will be just fine cant worry about price of gas, you play you pay