Wednesday, January 25, 2012

A Girl's Guide to Diesel Engines: The Oil Change

I can change the oil in a car, though admittedly the only time I ever did it unsupervised I created an Exxon Valdez-style oil slick in my mom's driveway and a tad bit of black smoke billowed up from under the hood when I drove down the highway. Still, I get the general gist.

Changing the oil in a marine engine is much the same principle, except, as with all things on a boat, it's a bigger pain in the butt.

Step 1: Turn on the engine. The oil has to be warm in order to extract it, so running the engine for a several minutes is essential.

Step 2: Get the old oil out of the engine. With a car this is a rather simple prospect. You just drain the oil pan, letting gravity work its, oh, so efficient magic. On a boat, however, you generally have to pump the oil out of an impossible to reach location down in the bowels of the engine. This is the oil pan access point where the dipstick resides, so get used to cramming your hand into this less than hospitable area. On some boats, you could conceivably drain the oil, but because most boat engines are shoved into a space slightly larger than the size of an Easy Bake Oven, it can be difficult. So you pump. And you pump. And you pump some more.

See the black tube? That's transporting our old oil.
Step 3: Take off the old filter. When you're done pumping out the old oil, you then take off the old filter using a filter wrench. Make sure to have a container of some sort that you can put underneath the filter as you take it off or you will get a ton of old motor oil all over your bilge. Not a fun prospect! Place the old filter in the container, and clean off any residue from around where the filter goes, taking care not to get any dirt or grime into the engine.

Step 4: Put on the new filter. Write the date and engine hours on the new filter, and put fresh oil around the gasket with your finger. Then screw on the new filter until it just touches the engine. From here you want to mark the filter with a Sharpie so that you don't lose your place, and using a filter wrench give the filter 2/3 of a turn to a full turn. Vlad recommends a full turn on a marine engine because a dislodged oil filter is pretty much death to your engine.

Put fresh oil on the black gasket.

Putting on the new oil filter.
Step 5: Put in new oil. On most engines, the oil filler cap is at the top of the engine, generally on the valve cover. Ours is no exception. You have to remove the oil filler cap (ours helpfully says "oil" and is bright orange), and place a clean funnel down into it. You then slowly add oil into the engine. Our Yanmar takes 2.6 quarts, but obviously check your specific engine manual for that number. Add oil until the dipstick shows a normal operating level of oil, which is close to the fill line, but don't overfill it. Replace the oil fill cap.

Yay! New oil!
Step 6: Run engine again. You want all the yummy new oil moving into the filter and other parts of the engine. After running the engine for a few minutes, turn off the engine, and check the oil level again. You'll probably have to add a little more fresh oil to get the level close to the full mark on the dipstick again.

We had some questions about what type of oil to put in the engine. Since we're heading off to exotic locales with equally exotic rules on sulfur content in diesel fuel, we needed an engine oil that can withstand a high sulfur content like CF instead of CJ-4 (sorry for the alphabet soup!). Evidently, some engine oil can be broken down by high sulfur fuel that is no longer allowed in the U.S., which is yet another thing I did not know and is definitely something to take into consideration when planning an out-of-country cruise. 


  1. I've changed engine oil many times. Good times. If you don't have a filter wrench, or yours, like mine always did, falls apart after three uses, you can always remove an old one by stabbing it with a screwdriver and using that as leverage to unscrew the filter.

    1. I've heard of the screwdriver method, though haven't ever had to do it myself. Thank goodness! But that reminds me, maybe we should stock up on filter wrenches.

    2. Actually, there's an advantage to using a screwdriver: the filter drains from a hole on the body rather than at the block, so less adhesion, and the oil is a little easier to catch. I grew to prefer the screwdriver method. Note that it does NOT work for putting a new filter on.

  2. Duly impressed. You go fellow sailor!

  3. Thank ya kindly, Ms. Charlotte! It's pretty fun stuff.

  4. I can not wait to change our oil.
    I mean that. Seriously.

  5. I am impressed with the access you have to your engine! Things like that are beginning to be more important to me.
    Question though. In step number 4, at the end where you talk about how dangerous a loose fuel filter is to the engine, did you mean to type oil filter? Or is the fuel filter somehow involved as well? I can see how a dislodged fuel filter could cause a problem. But same goes for the oil filter.
    I cannot say I'm looking forward to changing the oil, but I will make sure I know where the dipstick is located, and how contorted I will need to be to drain that sucker.

  6. Oops! I did indeed mean to type oil filter. That slip up even made it past Vlad, my eagle-eyed editor. Thanks so much for letting me know!

    The engine access on Bettie rocks. Which is funny to say since there's still a lot of contortion involved. Now that I've dealt with a few other boat engines I very much appreciate it.

  7. Hey, no problem! I would have been happy to accept that the fuel filter was involved as well, considering the amount I know about engines.
    The Cals are famous for their lack of engine access, a fact we didn't fully appreciate until Mike began to spend many vacations up to his shoulders in the engine compartment. It's something we really appreciate on other boats now.

  8. Thanks for sharing this, Bettie. That definitely made the oil change process easier and foolproof. Anyway, you can use synthetic oil for the engine. It is more efficient, because it can keep the carbon buildup on the piston and other parts of the engine low; which can lead to some mechanical issues. You can also ask your oil provider with regard to this matter for further reference.

    Abraham Yates @ Apache Oil Company