pet05

I want to start using the Mobil1 5W-40 synthetic diesel oil in my truck by this winter to help with cold starts. It currently has 10K miles on it. It should have around 13K by winter time.

raycarlson

10K ago was just fine

Arkapigdiesel

Straight from the factory is ok. Don't believe in old wives tale's.

DBLR

Being I don't know if you have hauled or towed much weight to work the engine hard to help seat the rings, I would say wait until you have 13K on it and then switch over to your synthetic oil. JMHO

doubledodge2003

im wondering when to switch myself. my truck has 15,000 miles on it, and has never towed anything other than my fat ***.

i was told by cummins not to run synthethics till about 20,000 miles

any ideas??

AH64ID

I personally switched at 13K and haven't burned a drop in the last 6K miles.

Amsoil says wait until you have acheived one full oil change interval. Thats 7500 severe service or 15,000 normal service....

In any event I would say your fine by 13K.

Hounddog

I waited to 15k

Dan_K

I did it at 17k, mainly to add peace of mind for the extended oil intervals.
I do alot of 4k#-6k# towing and will sample at 10k miles.

CD in NM

The factory recommended Valvoline oil is a synthetic blend, or better stated has synthetics blended into the mix. From that standpoint you have been running a percentage of synthetics.

I have stayed with the Valvoline oil for 30K, changing at the recommended 7500 mile intervals, my oil samples have been excellent. I added the Amsoil bypass filtration at 500 miles on the odometer, when I did my first oil change, I change the bypass filter every other oil change. When I calculated the difference in costs of the Valvoline vrs full synthetics vrs extended use possibilities of the full synthetics, I decided to get the bypass filtration, it's initial expense was clearly a better investment that would give greater benefits over time and long-term mileage than just changing over to synthetics. Plus, with the filtration and oil testing I can look at extended oil intervals. If I decide to go to full synthetics I already have the bypass filter to help control the soot/more damaging particles. Just some food for thought regarding options.

CD

Bigiron

I decided to follow Cummins recommendation and I'm switching over to Amsoil now at 20K miles.

oilfield-trash

Just changed to Lucas 15w40 syn. @ 179,000 miles. It was only $2.00 per gallon more so I figured why not.

zuki_dan

I switched to valvoline full synthetic 5w-40 @ 30k and installed my FS2500. I have been running 30K on the same oil and change filterand sample every 10k. At 30K miles my samples still come back good but the oil lasts me 1.5-2 years between oil changes.

DieselBoy20

I think Mobil 1 is a waste of money and that there are just as many other good/cheaper/nonn synthetic oils out there. I used to run it till it started to cost way to much money so I switched back to John Deere plus 50 15w40 which is non synthetic and I have been told by my mechanic that it is all he would ever use in any of his diesel motors.

Sevir

I did mine at 46k, i was told on this board almost a year ago that the break-in time should be done on dyno oil. and to fully break-in these trucks would be around 40-50k miles.

05mxdiesel

I changed mine over to amsoil at 21k and that is when I seen a drop in my wear metals via UOA compared to the dino Rotella I was running. I believe Cummins when they say wait until 20k not for breakin but to fully utilize the syn oil.