Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Stymied by bad oil change

I changed the oil on my wife’s Mazda3 today and it went off (as such a straight forward task is expected to) without a hitch. FWIW this is the first time I’ve done an oil change on her car. Just to note the steps, I drained the oil completely (it was filthy), removed the oil filter, replaced it with a new one, then added 4.5 quarts of 5W-20 as the manual recommends. When I went to drive the car afterward, though, it was sputtering a little as I drove it around the block, revving too much as I accelerated. By the time I started turning back, smoke was coming out of the rear tailpipe.

When I got back to my garage, I checked the oil level via the dipstick. It was like 2" ABOVE the max oil mark. Bizarre. If it was reading high, I thought I’d try to drain some oil out until it got to the right level. So I carefully took the drain plug out and oil started coming out at a very slow rate which was weird. I even took the oil cap off thinking maybe that would help it drain, but only about 0.5-1.0 quarts would drain before it started trickling. Totally bizarre. I then checked the dipstick to see if that did anything and it was still way above the max mark.

It would seem that there is some sort of blockage causing the oil to read high from the dipstick, but the oil pan seems to be empty. Any thoughts as to what could be causing this and a solution? I’m also wondering if I got a defective filter (which I confirmed after the failed oil change is the correct one).

Are you sure you didn’t drain the transmission fluid out of the transmission instead of the engine oil?

These plugs can be positioned very close and confused.


I’m Thinking You Drained Something Other Than Engine Oil, And Then Over-Filled The Engine (That Was Already Filled).

Are you absolutely sure that you drained the crankcase (twice) and not the transmission (twice)? If you filled the crankcase without draining it definitely would be overfull 4 quarts. Check the transmission fluid level (wipe and stab then wipe and stab again) All symptoms point toward the transmission slipping because of low fluid and the engine crankshaft splashing into the high oil level.

Hope this helps.

Tester’s guess is the most likely explanation, OP didn’t actually drain the engine oil, but something else instead, probably the transmission. That’s not an uncommon thing reported here.

Advice to OP: When doing an oil change, check your work before driving away. Before even starting the engine, visually verify you’ve installed the new oil filter on, the drain plug is in, there’s no oil leaking onto the ground, and the dipstick is at or near the “full mark”. Then start the engine, let it idle for 2 or 3 minutes, and look below the car again for the same things. After it idles for a few minutes, and there’s no leaks, turn the engine off and check the dipstick one more time. Then again after you arrive at your next destination.

Pro mechanics and the staff at oil-change shops should do this too, but for diy’ers, it is even more important, as diy’ers are less experienced and less well equipped.

Can you take and post a picture of the drain plug that you drained oil from? Seeing that location will help confirm what we’re all suspecting.

Also, does this Mazda 3 have a manual or automatic transmission?

I would not drive it this way, since you have some unit (transmission?) with no oil in it.

Yes, very important, do not drive this car !! until you get all the fluids corrected.

I also suspect something other than the engine oil was changed and the transmission is the first suspect.

Thanks for all the responses. I’m quite certain it was the oil that I drained. Transmission fluid is red. What I drained was stereotypical dirty black oil. This was the same fluid that drained from the filter when I removed that too.

I actually did check the oil level before driving and saw it was high. I was thinking maybe I had to drive it a little for it to level out. Clearly incorrect.

I’m wondering if the filter is somehow defective…

This vehicle is automatic.

If your transmission has a dipstick, I strongly suggest that you check it because despite what you are quite certain of, I think tester is correct. You would not be the first to do this and I will go as far as to say that better mechanics than you have done this too.

Old transmission fluid can be black too. It may have needed changing as well so this could be a blessing in disguise.


The oil filter of this vehicle is on the under side of the car and gets threaded on straight up. If I had mistakenly drained the transmission fluid, all 4.5 quarts of oil would have drained when I removed the filter, no? Only a cup or so did.

“all 4.5 quarts of oil would have drained when I removed the filter, no?”

That is incorrect

The engine oil filter holds a small amount of oil, far less than a quart in your case

If you have an engine with a full crankcase of oil, and decide to remove ONLY the oil filter, you will only lose what’s in the filter, not the entire amount that is in the oil pan. That is the case with the typical engines I am familiar with

For your scenario to pan out, the engine would have to be plumbed so that the oil filter was considerably below the oil pan.

By the way, the drain plug that you removed . . . what did it look like?

6 sided hex bolt, or did it have an internal hex?

If the latter, you almost certainly drained the transmission by mistake

For the sake of conversation, let’s say OP is correct, it was the engine oil that was drained and re-filled. Is there any other explanation for the high reading on the dipstick?

  • Too much oil put in.
  • Not all the old oil drained out.
  • Not reading dipstick correctly. Read it again after the car has sit for 12 hours, like overnight.
  • OIl filter is blocking the flow of oil for some reason. Or some kind of oil pump or oil filter bypass? I don’t see how this affects dipstick reading tho.

Of those, my first guess would be that too much oil was poured in.

@db4690 : I understand not much oil is actually in the filter, but the location of the filter (very low) would mean that all of the oil would have drained out of the filter orifice. The point I’m trying to make is that the oil pan would have been drained completely or close to completely by either taking the oil pan plug out or removing the oil filter. So even if I did drain the transmission reservoir, removing the filter should have removed most of the oil.

The oil filter is still above the level of oil in the pan, so when you removed the filter, the oil will stay in the pan.

The first time you drained it, did it come out slow and only a small amount came out? If the answer is no, you definitely drained the AT.

When I removed the plug when I did the original oil change, oil poured out as expected.

OP: to bypass all this argument, just check the transmission fluid level !!!

I’ll check the transmission fluid level tomorrow and update the thread.


I’m sorry, but you’re wrong

@keith did an excellent job summarizing it

Now what did that drain plug look like?

For that matter, the pan you drained . . . what did it look like?

Stamped steel or cast aluminum?

By the way, have you checked the transmission fluid level . . . I’m not exactly sure what model year Mazda 3 you have. My brother has a 2010 Mazda 3, and it has a transmission fluid dipstick, so for now I’ll assume you also do.

If the transmission fluid level is low, I think we know what happened. The transmission fluid level is checked with the engine idling, and the transmission fluid at operating temperature. After a drive, for example.