Closing the Gap: How much does it matter?

I own a 2017 Volvo 780 with D13 and Ishift and since it has broken in and I switched to full synthetic oil and been blessed with a series of really light loads my mileage has increased from the mid 8s to 9.7. Volvos typically have a lot of weight on the front axle so I had the fifth wheel set all the way back and figured I was getting great mileage so just left it there after my last heavy load but now that I’m close to 10 I have decided to try for double digits. I was at 9.7 when I decided to move the 5th wheel all the way forward and am now at 9.8. Have any of you run this experiment to see how much of a mileage improvement can be attained by minimizing the gap between the cab and the trailer? I pull a 53 foot box.

 

Yes the gap makes a difference, If you don't have them yet might want to put some Airtabs on to. Thy definitely help to get that air flow around the trailer and give you better stability in the wind.

 

your trailer will make the biggest difference. that air hitting the tandems.

 

All of our trailers are skirted but no air dams.

 

Did you record any numbers before and after installing Airtabs to see how much your mileage improved?

 

My computer on 1999 Detroit engine also shows 9.4-9.8 mpg, does not mean it's true. Do you fill up the tanks all the way, then divide miles driven by gallons used?

 

To many variables, there would be no way to do that with ant accuracy, Even if you had the exact same route every day things are always changing like the weather. Do you keep a 30,60,90 day average for your truck? In general the airtabs should get you 1-3ths

 

That is old tech. My truck is a 2018 so is much more accurate. Keeping track of gallons pumped and miles driven is far too much trouble and I would be unhappy if the results were less than the on board computer.

 

Now I know y'all like to hate on kevin Rutherford, but theres an app called "fuel gauges" just search for let's truck in app store or google play.

Literally 10 seconds to add a fuel entry and keeps track for any duration averages you like.

My REAL numbers are always BETTER than what the ecm estimates

 

Old tech that's the same "new tech" being done by a computer. It's nothing special. It's simple math a mind is a terrible thing to waste. I try to exercise mine often. Your truck is more accurate how did you check the accuracy?