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Once and for all, what is the proper weight oil for 2025 G550?
Hi all,
Seems to be some fuzziness regarding the exact proper oil weight for the 2025 G550. In the owners manual it mentions 0W-20 or I believe 5W-40. I've seen multiple different weights mentions here and elsewhere on line.
I just hade my first oil change done at my MB dealer, according to the service paperwork they used 0W-20 Mercedes Benz oil by the quart (not bulk oil), on the quart bottle it says its made by Fuchs?? I asked for an extra bottle to keep with me just in case, but the extra bottle is 5W-40.
So I ask.......What brand and weight do I want for my 2025 G550?
Several other forum threads discuss oil weight, and there seems to be a preference for 40 weight, as it retains better viscosity and lubrication at engine operating temperatures. I'm about to change my '19 G550's oil (4.0L V8 TT) and will be using Castrol 5W-40 Eurocar (API SP and MB 229.5). There's been a lot of discussion about 0W-20 sacrificing engine wear for fuel economy. GM's recent recall on its 6.2L engine failures include re-spec'ing 0W-40 in place of 0W-20.
BTW, FCP's price for the Fuchs 5W-40 MB229.5 is $32/5L jug if you're a DIY'er.
So if I’m understanding correctly, 5W-40 would be better for wear protection than 0W-20?
And regarding Fuchs oil brand. I have never heard of Fuchs oil before this latest oil change. No idea where it ranks in comparison to LiquiMoly, Mobil1, etc…
Bottom line, I want the best oil and the best weight for longevity
Bottom line, I want the best oil and the best weight for longevity
Some of the longest threads on the forum as this exact point....and they are confusing. For me, in each of my cars (6MB cars in the family I went to this....
I agree that is what the manual says. From what I glean from the many threads (and I have seen first hand in my cars). The thicker oil offers better protection and absorption of heat (at the cost of a tiny sliver of MPG - in theory). I KNOW that in my cars at about 2500mi into an oil cycle the start up is far quieter with thicker oil. I can always hear I need an oil change before I check the miles or wait for the light to turn on.
For me, I really like the Molygen. I like how acceleration is better with it (part of the solenoid conversation). I feel that it lasts about 2000mi more than Mobil1 0-20 before the oil degrades to the point that it 'sounds' like I need an oil change....I am sure 9 out of 10 of our peers can explain why I am wrong.
I spoke to Connor at Liqui Moly moments ago (888-665-9645). He was highly knowledgeable, clear and patient in his explanation of viscosities, approval numbers, temperatures, modern engines...specifically the new 6 cylinder in the G Wagon, cold starts, EPA suggestions of oil weights, gas mileage and on and on......Bottom line, he could have suggested several different Liqui Moly products, but he said for my 2025 G550, I ABSOLUTELY need to use Liqui Moly Top Tec 6610 0W-20 with the MB approval of 229.71
He stated that the new 6610 line in 0W-20 has ingredients and ranges that make it perform and protect like a heavier viscosity oil but it meets the characteristics required by the newest modern engines.
So, I gotta stick with what Mercedes and Liqui Moly state for use in the 2025 G550.
FCP does not stock it, Summit Racing does. $56/5 qt jug, free shipping.
MB engine oil specs are found at https://operatingfluids.mercedes-ben...ory/engine-oil. They do their best to make this all very confusing, but Sheet 223.2 summarizes oil specs by engine type. The 2025 G550 has the M256 engine (I think this is correct), and the 223.2 chart specs Sheet 229.71 and .72 oils for the M256.8 variant, 229.51 and .52 for the M256 Hybrid variant, and any of these for the M256.9 variant. Confused? I am. But from the footnotes, I conclude that 0W-20 should only be used in engines specifically designed for it, but this doesn't mean that these engines can't use a 30 or 40 weight oil (with a possible fuel efficiency penalty). An excerpt from a MB technical document on the M256 engine states that any of 229.51, .52, .61, or .71 are compatible (see attached).
It's interesting that the liter bottle of 5W-40 you bought is MB 229.5, and is not one of the low ash variants .51 or .52. I've been using MB 229.5 oils, and do oil/filter changes every 5K miles.
I spoke to Connor at Liqui Moly moments ago (888-665-9645). He was highly knowledgeable, clear and patient in his explanation of viscosities, approval numbers, temperatures, modern engines...specifically the new 6 cylinder in the G Wagon, cold starts, EPA suggestions of oil weights, gas mileage and on and on......Bottom line, he could have suggested several different Liqui Moly products, but he said for my 2025 G550, I ABSOLUTELY need to use Liqui Moly Top Tec 6610 0W-20 with the MB approval of 229.71
He stated that the new 6610 line in 0W-20 has ingredients and ranges that make it perform and protect like a heavier viscosity oil but it meets the characteristics required by the newest modern engines.
So, I gotta stick with what Mercedes and Liqui Moly state for use in the 2025 G550.
FCP does not stock it, Summit Racing does. $56/5 qt jug, free shipping.
I wonder what the actual difference is between the Liqui Moly 6610 0W-20 and Liqui Moly 6600 0W-20 oil then. Both are MB 229.71 approved but only the 6600 is MB 229.72 approved. The 6600 seems to have broader range of approvals while the 6610 carries the newer API SP specification. According to AI, "API SP is generally a more recent standard, often indicating improved protection against issues like low-speed pre-ignition (LSPI) and timing chain wear". I've been using the 6600 in my E450 (M256 3.0L i6 engine) and you can get a 5L jug on Amazon (
I wonder what the actual difference is between the Liqui Moly 6610 0W-20 and Liqui Moly 6600 0W-20 oil then. Both are MB 229.71 approved but only the 6600 is MB 229.72 approved. The 6600 seems to have broader range of approvals while the 6610 carries the newer API SP specification. According to AI, "API SP is generally a more recent standard, often indicating improved protection against issues like low-speed pre-ignition (LSPI) and timing chain wear". I've been using the 6600 in my E450 (M256 3.0L i6 engine) and you can get a 5L jug on Amazon (here) for $47. The 6610 is only $37 for 5L on Amazon (here). Much cheaper than Summit Racing and sold by Liqui Moly on Amazon so not likely counterfeit.
Hi Wolf,
The difference between 6600 and 6610 if I recall correctly was better ash protection 🤔 maybe. He did say 6610 was the "newer" 6600. The only place I could find 6610 was Summit Racing online. It arrives today.
Now that we know what oil, anybody know what crushwasher is on the oil plug?
My drain plug ('19 G550 / M176) is an M14-1.5, and the crush washer dimensions are 20mm OD x 14.3mm ID x 1.3mm thick. You can buy them in a package of 10 on Amazon for about what a dealer would charge for one.
Just here to echo that no matter the brand or weight, use the proper SP rated oils for any gdi engines. 5/40 is always a great choice for various climates.
You have a 2025? I am in the middle of my oil change right now (my25) and can’t even find the dang drain plug. I think they switched it to a plastic one..
Originally Posted by streborx
My drain plug ('19 G550 / M176) is an M14-1.5, and the crush washer dimensions are 20mm OD x 14.3mm ID x 1.3mm thick. You can buy them in a package of 10 on Amazon for about what a dealer would charge for one. https://www.amazon.com/dp/B07Q3NHPNL...n_title_4&th=1
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Once and for all, what is the proper weight oil for 2025 G550?
