Beware and look under the truck/motorhome.
When they removed the lead from gasoline for unleaded gas. There were some problems with engines that used the lead as a lubricant in some of the engine components.
Well, folks, they just did it to us diesel owners. Granted it was an infintesimal (sic) amount. But it was a lubricant for many of our engines o-rings.
The failure mode in the Ford 7.3 diesel is the o-rings in the fuel filter/drain lever fail. Fuel starts to leak. Some leaks are making the vehicle undrivable. The fix is a couple of "viton" o-rings for about $5.00. Of course, Ford is selling a kit for $39.00 or if mis-diagnosed is selling injector pumps for $800.00..
In some Dodge diesels the injector pump does fail. You will see fuel leaking from the injector pump.
You can replace the missing lubricant by adding an engine additive.
Ford folks can get the o-rings from a link on the Ford diesel web site. http://www.thedieselstop.com
Well, I guess that we can clean the air by losing fuel on the ground rather than burning it in our nasty diesels. So much for having a million mile engine in my truck. I expect that sooner or later the o-rings on my injectors will be effected. Meanwhile I will keep running an additive. I prefer Stanadyne. Some folks run Power Service or Lucas additive. Whatever it takes.