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It’s that time of year again for me to service my 2013 S4, specifically to replace the oil in the 3.0 TFSI Supercharged V6 up front. I thought I’d try something a little different this time though, specifically making use of this, the Liqui Moly Pro-Line Engine Flush. I picked this up for £10 with the notion that I’ll do it this one time at 68,000 miles just to see what it does. My engine isn’t excessively dirty as far as I can tell and has had very good service history and intervals so I’m not worried, but let’s give it a go.

How to use it is really simple, pour the whole thing into your oil fill port, start the car and let it idle for at least 10 minutes, optionally letting it get up to temperature might help dislodge any stuck crud, then shut off the engine and change the oil. Stick around to see if it made any difference!

So, changing the oil. That’s pretty easy on this engine – all you need is a way to lift the car even slightly, we just used some pretty small wooden ramps I made, a philips head screwdriver to remove the ¼ turn screws holding the undertray on – and in my case a T30 driver to remove the two T30’s also holding my tray on. You’ll need a drain pan to catch the oil – this 12L can style one is amazing, I’ll leave an Amazon affiliate link in the description to it, highly recommended.

A 36mm socket will let you crack loose the oil filter housing cap and remove the filter, and a 6mm allen key/hex bit will let you remove the sump plug and old crush washer and let the oil drain out into your drain pan. Once it’s all out you’ll want some shop towels to clean up the sump plug if you are reusing it and the area around the drain hole, and will make putting your new 14mm 1.5mm thick crush washer on before threading the plug in and using a torque wrench to tighten it to 30 Nm.

You can then replace the filter, I used this Bosch one which comes with replacement O-Rings that once you’ve pulled the old filter off you can use an angled pick to carefully pull out of the cap, then coat the new one in oil and push it in, then slide and click the new filter into place. Don’t forget to replace the thin O-Ring on the filter housing itself, I just squeezed it with my fingers to make it rise up enough to pull off, then again applying oil to the new seal before carefully sliding it on.

You’ll need to crack out the 36mm socket and torque wrench again to snug it down to 25 Nm, then a further 5 Nm as the cap says – I love when the spec is written right on the part, makes it so easy. Then use your 7L of oil – I’m using Liqui Moly 5W-40 High Tech which meets the VW 502/505 spec, but in theory any 502/505 or 504/507 spec oil will work fine, and anything from 0W-40, 5W-30 or 5W-40 should be fine, and your mileage may vary on how much oil you use or need as I only got around 6L or so out rather than the 6.8L the spec suggested.

If you haven’t picked up the “dealership special tool”, AKA the dipstick, I’ll put the part number on screen for you, and I’d recommend using it to find the correct level. It’s fine to fill it to a little over max since everything including the filter is completely dry. Once it’s there you can start the engine, let it build oil pressure, then shut it off and check the level again. Top up as necessary, and if you have oil spare it’s a good idea to keep it under your boot floor by the spare wheel so you can top up if needed.

Don’t forget to stick the undertray back up, then get your car back on the ground however you lifted it, and that’s it! It’s a good idea to stick your old oil into the cans you just emptied so you can take them to your local recycling centre – and while you are doing that you can check the oil and filter.

So, that engine flush… Did it do anything? Well this is purely anecdotal evidence and my opinion, not an objective test or result by any means, but on the whole I would say the oil is both darker than usual, and darker than what I’ve been monitoring on the dipstick including prior to adding the flush to the oil. There weren’t any deposits or lumps, but the filter was significantly darker than usual and I’ve actually driven the car a lot less this year so I would have expected it to look cleaner, not dirtier (without the flush). That’s a good sign.

For a tenner I think it’s worth doing once, especially at higher mileages, but I don’t think it’s something I’d bother doing every service. If nothing else I have a slight peace of mind knowing the internals are at least slightly cleaner than normal, so I’d call it a tenner well spent.



I have a passion for cars, driving, working on them and talking about them. Anything fast or electric, is fair game. Own an Audi S4 B8.5 & an SV650S.

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