Had some free time this evening so I decided to see if the CTS3 actually had any affect on fuel economy so I ran a pretty basic test with all the parameters being as even as possible and trips were done back to back, used the same pump and filling procedure, same speed and feathered foot off of starts and same route.

Filling procedure was fill on low till click, wait 10 second then top up on low till click and both times second fill clicked off at $2 give or take .25 cents.

Trip #1 was stock tune, trip speed was 102kph/1780rpms, 95.1km and took 17.153 litres to fill after equalling 13.04 mpg or 18.04L/100km

Trip #2 was with Roush 87 octane performance tune, trip speed was 102kph/1780rpms, 95.2km and took 15.034 litres to fill after equalling 14.89 mpg or 15.8L/100km

So results from the tuner gave me roughly a 1.85 mpg or 2.11 L/100km increase in highway fuel economy by my caveman math lol.

Of course there always variables and I'm not saying this is exact science or exact results, but these are just my basic caveman results and now I'm wanting to try a more controlled test using an external fuel tank going by amount of fuel left so all tests can start with the same amount of fuel to be more accurate.

Any suggestions on how to go about doing this fellas?

Thank you

 

i think you need a larger sample size to draw meaningful conclusions.

 

"Of course there always variables and I'm not saying this is exact science or exact results, but these are just my basic caveman results and now I'm wanting to try a more controlled test using an external fuel tank going by amount of fuel left so all tests can start with the same amount of fuel to be more accurate."

 

Sorry, let me rephrase: I think you need a larger sample size (more than an external fuel tank), to produce more meaningful MPG calculations.

 

​​​​​​​Feel free to post up some suggestions on how to go about doing so

Also I plan on doing the exact same test on my 03 ram 4.7 magnum and my 2012 Malibu if the tuner is compatible that is.

​​​​​​​Cheers.

 

Really I think the results are more meaningful if you had the same routes you drive on a regular basis and you have more of the tank you are filling and you produce the same or similar results more than a few times.

some of the variables you are trying to control like same route back to back, same pump are good ideas, but here are some possible sources of error.

1) If for argument sake the ~2 liter difference between the two trips is from fill level "error" that is a 2/15 =.13 or 13% error, whereas if you fill when the tank is more empty so it takes more like 80-100 liters to refill the tank then a 2 liter fill "error" is only a 2-2.5% error. In other words I have no idea how much variation there is in when the pump shuts off, but by dividing the amount of error into a larger denominator the error will have less effect on the overall calculation.

2) Was the truck already fully warmed up before starting the first trip? if not then thats going to knock down the average for that trip.

you just spent $50? in gas for giggles for this experiment. Thats your prerogative but for me I think I would just do my normal day to day driving for a few normal fillups on the stock setting and then a few on whatever tune you choose, and if the tune gives you consistently better mpg after a few fillups then thats more meaningful and just keep running that tune.

 

​​​​​​​Yes I will absolutely need to do more controlled testing to come to any conclusions and $50 in gas isn't a big deal.

Also truck had already been driven a few hours before testing was done so it was at full operating temperature and I even made sure heater was on same setting just to keep everything as equal as possible.