Engine Oil Help
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Joined: Jun 2023
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ML 350 2014
Engine Oil Help
Basically I have an ML 350 MY 2014 4Matic with around 125k miles, i used to put 5W40 oil but the mechanic said that 10W40 is better for high mileage engines .. How much true is that?
Should i change to 10W40 or just stay with 5W40 and will it make any difference as he said since my engine is high mileage (around 125k miles)
Does it matter for the engine changing from 5W40 to 10w40 or vice versa like should i do a flush first if i wanna do this change or it doesn't matter?
Should i change to 10W40 or just stay with 5W40 and will it make any difference as he said since my engine is high mileage (around 125k miles)
Does it matter for the engine changing from 5W40 to 10w40 or vice versa like should i do a flush first if i wanna do this change or it doesn't matter?
- Typical temperatures:
- Winter: around 5–18°C
- Summer: around 25–31°C
- Winter: around 5–18°C
- Driving style: Mostly city driving / short trips OR a lot of highway
Last edited by alexz350; Dec 9, 2025 at 02:47 AM.
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Joined: Dec 2009
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w166 2015 ML350, w203 2007 C230 Sport
You do realize that your question is one of the most debatable topics on the internet and is filled with subjectivity from various sources. Not to knock your "mechanic" but the most correct answer is what the manufacturer recommends. If you are/have been using 5W40 with no issues, why would you change? Also know that Mercedes recommends the 0W and 5W varieties of oil viscosities on most of their modern engines where the 0W and 5W are thinner oils at the starting temp versus the 10W. You stated your use was:
- Typical temperatures:
- Winter: around 5–18°C
- Summer: around 25–31°C
- Driving style: Mostly city driving / short trips OR a lot of highway
- 0W-40 or 5W-40 full synthetic motor oil, depending on climate and engine type
- Oils that meet or exceed European ACEA A3/B4 or C3 ratings
- OEM-approved brands like Mobil 1, which is factory-recommended
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Joined: Nov 2025
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From: US
Mercedes SL R231
I’ve got 130,000 miles on my 2014 C350 and I use an API SP rated 5W-40 oil, and have no intention on changing that. API SP is a new formulation that mitigates the risk of Low Speed Pre-Ignition (LPSI). I personally would not go with 10W-40, but I do use 5W-50 in my 21 year old Audi with 254,000 miles.
Change oil every 3000-5000 miles.
Change oil every 3000-5000 miles.
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Joined: Oct 2023
Posts: 117
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From: Buchanan, SK CANADA
2013 ML350 Bluetec
If you are losing significant amounts of oil (more than a litre every 8 or 10,000 km) then I might agree with your mechanic. In my case, I have 300k++ km, burn absolutely no oil between 8,000 km changes and use Rotella T6 0/40. My car is fully deleted so I'm not concerned about preserving the DPF. I want lubrication IMMEDIATELY on startup because my understanding is that most engine wear occurs within seconds of initial startup. I run that same 0/40 synthetic oil in every diesel I own which is probably overkill but its what I do.
