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Wednesday, October 4, 2023

Doug's Domain

Doug Vetter, ATP/CFI

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Doug's BMW E36/E46
DIY Oil Service

(Image: Performing a DIY oil service)
Engine oil service costs approximately $120 at my dealer,
but it only costs me $35 in parts and an hour of my time


I schedule an oil service on the E36 328is (M52 engine) every 4500 miles, or half the recommended interval of 9K miles. By that time even if the oil isn't completely broken down, chemically speaking, it's usually pitch black and should be changed simply to prevent sludge deposits from forming. The newer M54 engine in the E46 330ci burns cleaner than the M52 and can indeed go 7500 miles between changes.

Oil analysis has proven that modern oils like BMW 5W-30 will last approximately 12K miles before breakdown so it's certainly possible to wait until that point, but there are two reasons why I recommend replacement earlier than that. First, there is risk that the paper oil filter insert will fail before then. Second, all oil eventually reaches a point where it can take no more particulate matter in suspension. It's not hard to speculate where all the gunk will go from that point on.

IIn any case, BMW's recommended 15K or higher oil service interval on modern vehicles (E36 or later) is as ludicrous as is the notion of a low-maintenance high performance automobile and they are gambling the health of your engine with your money. Do yourself a favor and do regular oil services at half the recommended interval. It's cheap insurance.

I also recommend that long term owners start an oil analysis program at 150K miles to develop trend information that may give advance warning of internal engine component failure. Blackstone Laboratories provides a detailed and timely report for a reasonable cost that can be easily "paid" by the labor savings that result from doing it yourself.

(Image: Sample BlackStone Labs Oil Analysis Report)Prerequisites

This article assumes you're working on a late model non-M E36 or E46 with black plastic filter canister cover with 36mm fitting. If you have an older engine with the metal cover and smaller bolt, you will need to research the proper assembly and torque specifications on your own.


  1. Warm the engine oil. An oil change should be done with the oil warm to the touch. The goal is to get the oil warm enough to flow easily – it does not need to be anywhere near “normal operating temperature”. In fact, the hotter the engine, the longer you have to wait to get near it or you risk scalding yourself with hot oil or burning yourself on various hot engine parts.
  2. Put the front end on ramps or jack it up on a rigid surface (concrete or THICK, COLD asphalt). Note that metal ramps should NOT be used unless you are working on concrete. They can slice through hot asphalt or other less rigid surfaces and drop the car on you. If you have questions about how to jack up a car now, STOP RIGHT HERE and educate yourself on proper jacking procedures before you kill yourself. Re-read my site disclaimer while you're at it.
  3. Remove the oil filler cap from the top of the engine and set it somewhere outside of the engine bay (preferably on a nearby table or desk).
  4. Loosen the filter cover using a ratchet or breaker bar and the special 3/8” drive 36 mm 6 point socket.. You needn't pull it out right now...just fully release the threads.
  5. Get under the car and remove the drain bolt. I typically break it loose (counterclockwise) with my breaker bar or ratchet (either will work...it should only be torqued to 18 ft*lbs) and then unscrew it by hand while keeping pressure on it toward the block. This helps prevent oil leaking on your hands as you remove the plug. Don't drop the filler bolt into the drain pan. You'll just create a mess trying to fish it out of the pan later. Put the drain bolt in the same place you put the filler cap. You do NOT want to misplace this bolt.
  6. Do something else for 20 minutes. Yes, it really takes that long for the oil to drain out of the engine, particularly if you just shut it down. This is because a lot of oil is still in the top-end of the engine (and the oil filter) and needs to drain down to the sump. This is the number one problem with those quick-change places (and, truth be told, many dealers). They don't wait the requisite amount of time and you wind up with ½ quart or more of old oil mixed in with your new oil...which throws off any oil-analysis you might do, and almost assures you will overfill the oil.
  7. Pull the filter assembly from the engine canister and remove the old oil filter. Put the filter in a zip-lock bag and set it aside.

Now, for reassembly.

  1. Reinstall the drain plug. Make sure the drain bolt is completely clean (clean with brake cleaner or similar if you screwed up and set it down on a dirty floor), install a new crush washer from the filter kit, reinstall the drain bolt in the oil pan, and torque the bolt to 18 ft*lbs (25 nm). Always use a torque wrench and be sure you don't overtorque the drain bolt. The cost to fix that mistake (properly) costs far more than a good torque wrench, so don't be stingy with the tools.
  2. Clean the area of the oil pan near the drain bolt with some brake cleaner. This will allow you to spot leaks later and prevents dirt from accumulating there.
  3. Coat each o-ring in new oil and install them on the filter assembly. This is particularly important for the large o-ring, for if you avoid this step the filter assembly will not rotate easily in the canister. Note that installing new “small” o-rings is based on condition (they last a long time), but replacement may be considered good practice every other oil service.
  4. Optionally, open one quart of oil and pour it into the center of the oil filter canister. This will help prime the system so the engine doesn't run as long without oil pressure.
  5. Install the new filter. Install the new filter on the filter assembly, (the BMW OE filter insert has no up or down – it can go on either way), reinsert the assembly into the engine filter canister, and torque the cover to 18 ft-lbs (25 nm) OR the torque specified on the cover itself. This is a very light torque in any case.
  6. Fill the engine with the remaining quarts of oil and then reinstall the filler cap. It should rotate 90 degrees until fully seated.
  7. Clear the engine bay of any towels, gloves, and tools and then start the engine. The oil pressure warning light may remain illuminated for a few seconds more than it usually does, but it should go out within 10 seconds at most. If it doesn't, shutdown the engine and figure out what is wrong before you run the engine again. Is there a puddle of new oil under the car? Did you forget to replace the drain bolt?
  8. Check for leaks. With the engine idling, look under the car for leaks and then put the front end of the vehicle back on the ground. Optionally, go for a short drive. The oil pressure light should never illuminate during this drive. When done, park the car somewhere level (both fore-aft and left and right) so you can...
  9. Check the oil level after the car has been sitting with the engine off for at least an hour. This will give you the most accurate reading. The level must be within the min / max marks on the dipstick. I find that 6 bottles of BMW 5W-30 puts the level about 3mm above the minimum mark. Non-M BMW engines typically don't burn oil in daily driving (in fact, I have never needed to add oil between oil changes), but if your particular engine is outside the statistical averages and burns some oil you may want to buy another quart so you can add more when necessary.


The oil level reading is only accurate when the car is level. You cannot effectively check the oil level when one axle is on ramps or jacked up, or when the car is on a sloped surface. The crown built into some residential streets may even be too much. I say this not because the engine will explode if the level is slightly out of the range. The reason I point it out is that you should NOT make the call to add or, worst case, remove oil based on the level shown on the dip stick if the car is not perfectly level.

Please do not put used motor oil down the drain, into the gutter, or the ground, or throw used filters into the household trash. It should all be brought to your local HazMat facility. Remember -- other people live here too.


Servicing of engine oil is probably one of the most important things you can do to prolong the life of your engine. Properly maintained BMW engines will last at least 250K miles and there are a surprising number of engines going strong with 300K or more without major engine work. Remember, however, that engine oil is only one of several critical fluids that must be changed on a regular basis. I strongly recommend you ignore BMW 's marketing propaganda and replace all other fluids in the vehicle (differential, power steering, and transmission) at regular intervals, or you will indeed learn how expensive a BMW can be to maintain. Look to this site and others for more information.

Now, after reading this, you're probably asking yourself "should I go out an buy tools so I can do my own oil changes on my BMW?" I'd have to say "no", and here's why. Interestingly, oil changes are considered by many dealers and independents as loss leaders, which means they intentionally keep the price of an oil change down in order to get your car back into the shop for more costly repairs. For this reason DIY oil changes do not provide as great return on investment as other, more involved repairs such as brakes or suspension work unless your dealer charges $200 for them and your time is worth nothing. There's simply not enough of a labor savings involved to make DIY oil changes financially practical. You'd have to do at least four changes just to break even on the tools required and for some people that's three or four years worth of driving. I mean, hell, if you're going to do one oil change a year, just take it to the dealer.

That said, however, I now do oil changes myself because I drive enough milee to do three or four changes a year, the job is usually performed in conjunction with some other work I'm doing, I can spread the cost of the tools over other projects, and because every dollar I save doing work on my own -- even if it's $50 here and $100 there -- helps to buy a tool for another task or just reduce my overall maintenance budget. So, while I'm content doing my own oil changes, I don't officially recommend people DIY unless you can justify it for some reason OTHER than saving money, like education or simply pride in one's own work.