Q: When I vi sit my father and use his Mercedes he always tells me to make sure I don’t run the gas tank down to empty because when a diesel runs out of fuel it’s a lot more complicated (and expensive) than a regular car to get it running again. I think that’s probably just Dad-talk for “Don’t bring the car back close to empty.” But since I haven’t done that for more than a decade, maybe there really is a problem and this is not just an old dad’s tale! What’s the scoop?

A: Time for you to apologize to Dad for doubting his word. Diesels require a little extra TLC once they’ve been re-fed after running on empty. Something called a primer bulb will do the trick in most situations. But sometimes a technician may have to do some under-the-hood maneuvers. You can get all the details about your dad’s specific vehicle from the owner’s manual.

Q: My brother-in-law is one of those handy guys who likes to save money by doing things himself. That includes changing the oil in his two trucks and my sister’s car. I’m glad he puts the old oil drained from the car into a big bucket that he claims he takes to an appropriate place for disposal or recycling or whatever. But he’s not a neat man, or a particularly careful one, so when I watched him change oil in his two trucks last week I saw lots of it wound up on the driveway in a nasty pool. Apart from the ugliness of his dogs walking through it and tracking it into the garage and house, isn’t there some environmental impact? I know I can’t convince him with save-the-planet arguments, but if I give my sister some decent information, she can usually get him to modify his practices. I just don’t know where to look.

A: I can’t begin to think why the driveway muck hasn’t already driven your sister to bolt his favorite lawn chair right on top of it and chain him to it. Perhaps she’s an uncommonly patient woman. Perhaps that’s why she still has a husband and the rest of us hotheads don’t.

Anyhow, if you think arguments about the environment would be more effective than the reality of gummy feet (human and creature), the ankle-breaking driveway oil slicks when it rains or the 1950s-repair-shop stench that accompanies such blight, here you go:

When it rains or when the lawn sprinklers hit it, the oil will get washed into the groundwater. That’s probably not a huge deal if he’s the only one leaving that glop in his driveway. But if many other people in the neighborhood or the town create a similar blob (from sloppy oil changes or from leaks), it adds up. Eventually, oil sheen can form on a pond or lake where it all winds up making it impossible for aquatic life to continue to live. Moreover, one quart of oil can contaminate 250,000 gallons of drinking water, according to the Tennessee Department of Environment and Conservation.

Truth is, I hadn’t really thought in global terms about a DYI oil-change problem until this question arrived. Turns out it’s a bit more of an issue than I would have thought – so much so that the aforementioned TDEC and the Middle Tennessee State University Center for Environmental Education teamed up and hired a big-shot Nashville firm to inform young drivers about the problem and ways to keep motor oil and other vehicle leakages out of water sources. A series of public service spots explains how you can tell which fluid is leaking (transmission, brake, etc.), what the environmental risks are and asks that Tennesseans become more careful to avoid spillages, even little ones.

Although the campaign didn’t make specific note of sloppy at-home oil changes, it does say that Tennessee do-it-yourselfers generate more than 1 million gallons of used motor oil a year. Guess there’s a lot of weekend car work going on that I never suspected. Anyhow, the campaign makes some pretty compelling arguments about cleaning up the messes (with kitty litter, sawdust or a product called “Oil-Dri”), repairing whatever one needs to repair to prevent future leaks, and ensuring appropriate disposal, preferably at a recycling station.

The campaign encourages recycling, since it “it takes 42 gallons of crude oil but one gallon of used oil to produce 2.5 quarts of new lubricating oil,” according to the experts. Also, re-refining oil takes only about “one-third the energy of refining crude oil to lubricant quality.”

You can find out more at tdec.net.