Hi all,

I feel like an idiot for asking this, but here goes: how, or rather, when, do you correctly measure the oil level? Cold? Hot? I get varying readings depending on whether I check it in the morning w/ a cold engine and at the gas station with a hot engine after it's been sitting for 3 minutes to let the oil drain back into the pan.

Tonight was the kicker - at the gas station this afternoon, the engine read half a quart low. Drove home, parked the truck, finished some chores, went out after about 4 hours to check the oil again. Oil level was perfectly fine. Checked again, dipstick read a quart low!?!? Checked 4 more times, and each time the dipstick read full. What gives??

Truck's a '92 F150 5.0. Oh, and I seem to have a similar problem with the 390 in my '67 Cougar. Was school just wasted on me?

Flustered in Cali,

-R.

 

Measure it cold and on a pretty much level surface. That's when all the oil is in the pan. If it read half a quart low at the gas station it's probably cause you just stopped the vehicle and some of the oil is still up in the engine and missing from the pan. But it shouldn't take all that long for most of it to drain back. If I check it at the gas station, I'll let it sit for a couple minutes and check it. But the best time is after it's been sitting a while. 4 Hours should have been plenty. And if it was a quart low on one check, then you probably stuck in the dipstick and pulled it out too quickly and didn't let the oil attach itself to the stick. Put in the dipstick in and let it remain for a few seconds and then pull it out. I always check it 3-4 times anyway just to avoid the problem you just went through. Also look at the back of the dipstick. Sometimes the stick can go in at such an angle that you have to average the levels of the front and back.

I don't think school was wasted on you, you're still learning and know how to ask the right questions by giving all the facts. That's pretty smart.

 

Hi Qman,

When I check at the gas station I typically fill up the car first, which on the truck takes a cool 5 minutes (slow pumps here). THEN I proceed to check the oil level. Still I get varying readings.

I'll check the levels cold from here on out, and remember to average the front and back of the dipstick.

Thanks for your input!

-R.

 

Filling the truck first is the way. 5 minutes should also be enough time for you to get a good indication. But remember how you do it when you do an oil change. You drive the car so its warm (not necessary but I think it drains faster.) Drain old oil, remove & replace filter, re-install plug, and refill with oil. I run it for a couple minutes and then shut it off. Let it sit for a few minutes and check it again. That's pretty much the same as you letting it sit for 5 min at the pump. You shouldn't have that much variance on your stick. Just do it a number of times and take what happens most as you level.

 

i always check the oil on a hot motor. i would rather have a bit to much in there than not enough. on my big trucks, the difference between hot and cold is 1 gallon.

 

Just don't go overboard TJC.... you don't want the crank to pick up too much in the "wind" it creates - it robs horsepower and aerates the oil.

I had the pleasure of watching an engine run on a dyno, where a small camera was installed inside... the oil was overfilled, and it looked like a butter churn inside, at least until the camera was completel gooped.

 

yea, i know what you mean frederic. all my motors read 1/2 quart over cold and on the mark hot. i always let them sit for at least 2 min before coming off idle, so there is no worry about foaming. the mack trucks and the old cummins 350 are the ones that have the gallon difference. some of the older cat diesels were checked running. the difference on them was as much as 2 gallons, depending on size of motor. there was 2 marks on the dipstick. cold and run.

 

the only bad question was the one that wasnt asked!!!