Diesel Fuel for 2007 Cummins ISL 400HP Engine

It can cost you close to 5K if you guess wrong. DPF filters are not cheap. Towing is not either.

It may depend on exactly when your 2007 was built - some motorhomes were still using 2006 chassis and engine in 2007 models - early ones anyway. There is probably a way to tell but I can't explain it. As far as using Mexican diesel in one of the newer engines that require ULSD - there are people who do it and people who say it can be done - most reports we have read relate to pickup trucks which are not motorhomes with 400hp Cummins engines. I have no idea as I make no claims to any expert knowledge - about much of anything. Here's the thinking I come up with - the new system is built and intended to operate on 15ppm sulfur while the fuel in Mexico could be 500ppm. So the thing that is supposed to clean your exhaust has to somehow clean 500ppm while it is designed for 15ppm. This could mean it has to heat up and burn off sulfur more frequently than designed. Will this ruin it? I have no idea. But it could shorten the life of the equipment and I have read it can be expensive to replace. I always suggest checking with the engineering at the manufacturer - that being Cummins - and not the corner mechanic - or a dealer - or anyone on an internet forum you know nothing about - including me.

Robt: You may be lucky. Most of the Monacos in 07/08 that were ULSD had the 425 ISL. If you open up the engine hatch and look down at what appears to be a muffler see if it has some sensors and a line that brings diesel to the "muffler". If so it is a ULSD engine. You can also look up the serial # of your engine and call Cummins.

Moisheh

If your MH has a DPF then it must use ULSD. If there is no DPF then you should be OK.

ULSD is required for 2007 highway
model engines.

• 80 percent of highway diesel fuel
must be ULSD (15 ppm sulfur or
less) beginning June 1, 2006.

• Use of fuel other than ULSD in 2007
highway model engines may cause
damage to the Catalyzed Diesel
Particulate Filter