ISX CM871 Problems on multiple trucks

Hello all I am looking to get some advice. I recently started as a tech at a local shipping company and because of employee changing landed in the spot of garage supervision. We have a total of 20 trucks and 8 of them have the ISX CM871 engines. I have taken the advice from Rawze and preformed a EFG cleaning on each of the trucks and ended up having the turbos replaced on 2 actuators on 3 and DPFs and other things on 3 of them, all DPFs have been either cleaned or replaced on the trucks and overheads run on them. The MPG report from last month was just posted today and we are not showing any gains within the 2 months that everything was preformed. We are also starting to see spikes in soot content from all of the trucks, and raised lvls of lead, zinc and sodium. We had suspected that the bulk oil that we are using (gaurdol Titan 15w40) may have been the culpirt. After some reading into and getting the spec sheet from the provider the specs either meet or exceed CES20081 so we are thinking that this is not the issue. We are also changing from Donaldson filters to the FleetGaurd filters that Cummins Specifies. I have sent our OA to 3 seperate companies from the same fill to verify that the readings are the same between the OAs and that we are not getting false positives.

The average between the trucks was 5.3mpg, these trucks are limited to 1500 RPM and range between 6 386Petes a 388pete and a volvo. All 13spds with different axle ratios. The top MPG from our cummins trucks is actually a IXS15 that we have no trouble with at 6.2mpg the lowest is the volvo at 4.9. I am all out of ideas on what we can do to raise these numbers and not cause a lot of downtime. A oil rep from one of the OA places recommended a diesel fuel supplement called DZL clean because he said that his lad techs said it was a fuel issue not a oil issue, but i am weary to try any kind of snakeoil because of the cost and the limited feedback that I can find.

Can anyone suggest something that we can try. I like these trucks they all have been easy to work on and the only thing giving us fits is the issues above. We can not do deletes as we go to california.

 

Only one of the trucks has an APU and it is the ISX15

 

Ok guyssorry about tge delay in responses. Been kinda busy here this week.

The truck gearing varies and i wilm have to pull tge books on them when i get back to the shop. All of them run 295/75/22.5 except the volvo which runs 11R22.5.

Loaded weight varies anywhere from 10k to 50k anc they all pull van trailers. I have been on them to pull closer to the cab if they can. They all pull variying terrain we have 4 that run from SD to CA weekly.

Dosers are either good working units or hsve been replaced. We have been cleaning and inspecting sensors at every grease and service. We are only getting 17k between services because of soot buildup. I recieved the oil report on the 388 today and even after all new sensors and cleaning,dpf replaced, new doser, and turbo soot content is still raising.