A couple months ago I bought a 2017 cargo 170 ext 3500 4x4 off the lot in Canada. I'm in the process of converting it into an RV but while It's been empty I've made a few long highway trips and I am starting to be concerned with the fuel economy. On average, It stays between 14 and 15 l/100km (16.8 - 15.6 mpg) on the highway. This is on a combination of flat, rolling, and mountain pass terrain and doing 90 - 110 km/h (55 - 70 mph). It'll climb towards 16 if I am only driving up a mountain, but usually things will even out and come down to just under 15. The fuel light will come on consistently around 450km (280 mi), and I can push it to about 580 before I need to stop.
I am concerned for a couple reasons:
1. The Mercedes sprinter sales folks have consistently seen 11 l/100km (21.3 mpg) in the same van as mine, fully loaded on the highway, and around 12-13 in the city.
2. I'm seeing older sprinters get better mileage. A specific example is a 2014 170 ext airstream interstate, fully loaded, getting 13 l/100km over mountain passes. This example is from today. After 440km, 5h 12, over 5000ft of elevation gain averaging 86km/h he ended up with 13 l/100km, a half tank remaining and estimated range remaining of 420km. This is obviously a bit slower than 100 km/h average, but I've only actually seen 13 a few times at the start of trips and it always rose pretty quick into the 14-15s from there.
I've already had it in to the dealership. They updated the CDI software, but otherwise saw no issues. Their report said they were getting 10.6l/100km on a highway test drive. I took it out right after on the highway and managed 14.1 for ~50km at 100km/h.
Does this seem worth investigating further? If so, how would I go about it considering the dealership has yet to find an issue?
I am concerned for a couple reasons:
1. The Mercedes sprinter sales folks have consistently seen 11 l/100km (21.3 mpg) in the same van as mine, fully loaded on the highway, and around 12-13 in the city.
2. I'm seeing older sprinters get better mileage. A specific example is a 2014 170 ext airstream interstate, fully loaded, getting 13 l/100km over mountain passes. This example is from today. After 440km, 5h 12, over 5000ft of elevation gain averaging 86km/h he ended up with 13 l/100km, a half tank remaining and estimated range remaining of 420km. This is obviously a bit slower than 100 km/h average, but I've only actually seen 13 a few times at the start of trips and it always rose pretty quick into the 14-15s from there.
I've already had it in to the dealership. They updated the CDI software, but otherwise saw no issues. Their report said they were getting 10.6l/100km on a highway test drive. I took it out right after on the highway and managed 14.1 for ~50km at 100km/h.
Does this seem worth investigating further? If so, how would I go about it considering the dealership has yet to find an issue?