Another Diesel Question From a Novice.

[sisu]

We were out & about giving the used camper a run to see what else needs to be fixed, caulked, replaced etc. I noticed my milage was good on the highways (55-65 mph), but we did a side trip from Thompson Falls, MT to Thompson Chain of Lakes on a nice dirt road that went the usual 15-30 mph depending on the road conditions. The milage sunk by about 3 mpg, I am thinking this would be normal as we did not keep a constant speed, the engine & trany were working hard on the hills and constant speed change for the road conditions.
Since I have a automatic is it advisable to shift into 2 instead of drive on roads where you don't go past 30? I did for about 1/2 of the dirt as it meant I did not have to use the brakes.

Like I said in the heading complete novice in regards to the diesel.
Thank you for any & all help
S

[jeepasaurusrex]

Your mileage dropping is normal for those conditions. I am guessing your are reading the onboard mileage computers readout. I don't put much faith in those anyway.

I try to keep my RPM's up, but not excessive. Downshifting to 2 to keep the RPM's in the optimum range will help. When I am towing the travel trailer up steep grades on dirt roads, I will drop it into 4wd low range to make things easier on the transmission. A huge killer of transmissions is heat. Unless you already have an axillary tranny cooler, I would suggest installing one. The slow speeds on dirt roads do not supply enough air movement to effectively cool the transmission.

Also, you did not mention what make/model of truck you have.