You could stop at the auto parts store and buy a diesel fuel conditioner that you simply add to your fuel tank. Get one that says it helps your injectors stay clean. Make sure the garage changes your fuel filter if your due for a new one and they drain any water in the filter at the same time. Never let the tank go too low and run out of fuel because all the water and crud on the bottom of the tank gets pumped up into your fuel filter and injectors and causes BIG problems. When you see the tank at 1/4 full, I'd start watching for a diesel fuel station for a fill up. You may need a new air filter too every 15,000 miles or so for standard driving. If your engine has trouble starting the first time in the morning, that usually indicates you have one or more bad "glow plugs" that need replacing. They burn out all the time on a diesel.