Checking the oil level

I have to admit that checking the oil level is a little frustrating to me, both on my XJ with the oil window and my Hondas with a dip stick. For example, yesterday before a ride I checked the oil in my XJ and it was about mid-way so I started it and let it run for 4-5 minutes, shut it down, waited about 5 minutes and it was still about mid-way. So, I added about 6 oz of oil, but it still didn't reach the top of the window after about 5 minutes but I figured that was enough. Took an 80 mile ride and immediately checked the oil level when I returned and it was slightly beyond full--i.e. no bubble at the top. A very slight tilt and the bubble appeared. I checked again after about 20 minutes and still no bubble. The bike was on the center stand in the same place on my drive way before and after the ride and there is no gas in the oil. I can only assume that the volume of oil expanded with the engine at operating temperature. I have had similar results after changing the oil so I am curious about what is going on. Any ideas?

 

Yup, oil expands slightly with heat. That's why some cars will have a "cold" full and a "hot" full mark on the dipstick. If some nerd wants to go into details about the coefficient of thermal expansion of motor oil, you'll get a more specific answer.

Hot oil flows a lot better, so it's easier to change oil when the bike is warm, but obviously the oil you put in is going to be cold. My xj750 owners manual just says to add 2.5 quarts when changing the oil without filter replacement. Personally I'd measure that out in a separate container, then when you add it you don't really have to worry about the fill line because you know you put the correct amount. Then make a mental not of where that amount of oil looks in the fill hole both cold and after warming the bike up a bit.

 

I recently changed the oil and filter and when refilling I kept checking how much I added. Once I got to the recommended amount I still didn't see anything in the window. I added a bit more and then more and then more until it was about half way. I'm thinking"Where does it all go?". After a ride I check and it is to the top or more and remains there still. When I get a chance I will drain a bit out. Very frustrating.

 

It's a wide oil pan, lotta area for the oil to spread out. Plus ~2.5 quarts really isn't that much which is why it's so easy to overfill. I personally am a big fan of the "fill till it leaks out the fill hole" type oil cases like on the final drive or the rear differential of my Forester. It's much harder to f*** those up.

 

Where do you guys get this 2.5 quart idea?

The side of the crankcase is marked 2500cm3 - that's 2.5 liters. Which is not the same as 2.5 quarts. It's 2.63 quarts.

However, more to the point, the factory manual says to add 2.9 liters (3.1 quarts) of oil to a freshly rebuilt engine.

2.5 quarts may be right if you don't have an oil cooler, aren't draining the middle gear, and don't change the filter... but it still sounds a bit low based on all this other factory data.

Edit: Nevermind. I found where the factory manual also says 2.5 quarts for a non-filter change, and 2.65 with a filter change. OK. And that's with (from what I can see) draining the middle gear (which most of us don't do, because it's risky).