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I have a C250/M271 and I'm wondering what the best oil weight is for this engine? (Already assuming MB approved oil, regardless of oil brand). Just a question about oil weight -
5W-30 or 5W-40? I live in SoCal, mild climate. Any drawbacks of one versus the other?
I use Mobil one synthetic European car formula.
0-40 here but in nicer weather 5-40 is fine also.
And with synthetic you only need to change every 10k miles butt I just do mine twice a year.
Last edited by RobertR728; Jan 3, 2025 at 09:57 PM.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
DO NOT use long change intervals if you want a long life for your engine. 10k miles is too long and only marketing hype while manufacturers try to outdo each other. Keep change intervals to 5000 miles (or 6 months) max. Fluid changes are critical to the health of your drivetrain. That means you also need to have the transmission serviced on time.
When selecting an oil, make sure it is API SP rated and MB 229.5 approved. A 40 weight will serve you better than a 30 weight, especially in warmer climates.
I am with @JettaRed , you want to change your oil more frequently at 3-5k miles. NEVER wait until 10k miles to change your oil.
as far as oil weight goes, I would stick with the 40 weight. Also, check out the YouTube video from “the motor oil geek” he did on Mobil1 oils.
I switched to liquimoly MolyGen 5w-40 and have had no issues. I’ve been running it for over a year now and have put thousands of miles on the car without skipping a beat.
everyone has their preference of oil manufacturer, but if you get a quality oil and change your oil frequently enough you’ll be fine!
Thanks guys. I’ve been going with 5k mile OCs since I bought the car at 30k miles. This upcoming oil change next week will be about a 3.5k mile interval (at around 8 months).
I’ve seen a few of the motor oil geek videos, I’ll check that mobile one out.
The reason I brought up the oil weight is because I have a service appt with a local MB specialist, and I went there once before a couple years ago and they’re the only shop that ever used a 30 weight. I’llask them to use a 5w-40.
Last edited by WestonMerc; Jan 4, 2025 at 11:36 AM.
0W-40, 5W-30, 5W-40 won’t matter unless you drive in extreme environments. We have a small fleet with well over 1 million miles on Mobil 1 0W-40 and Castro 5W-40 229.5 oils. We drive a lot, so our OCIs aren’t applicable to you. We just switched to LiquiMoly 5W-30 because our new vehicles require low ash oils and that brand is easier to find in that spec. Mobil 1, Castrol, LiquiMoly, Pennzoil Platinum, Shell Helix, Motul — We have run GC analyses on the base oils and chemical component analysis on the blends. They are all different, but all fantastic lubricants. You pick the one you like and can easily get at a reasonable price, just make sure it says Mercedes Approval 229.5.
Out of the 5w30 or 5w40 I would use the 5w40 if I were you. Looks like the 5w40 operates in higher and lower temps. Im sure your car will see +86 degrees in summer.
Im in New England so see hot summers into the 90's then winters in the single digits once in a great while. I use the Mobil1 0w40 because it is low cost locally and I used it in my previous vehicles so im just used to getting it.
Based on the chart in the back of the Operators manual. Your manual may be different.
Interesting chart. I’ve seen it before but never really looked at it closely.
After doing more research - I also want to go with a 40 grade because I’m concerned about fuel dilution. Anything I can do to help the timing chain last longer and who knows - head off the cam phaser troubles. The car has 68k miles, hoping to keep it least until around 130-140k miles.
I have a C250/M271 and I'm wondering what the best oil weight is for this engine? (Already assuming MB approved oil, regardless of oil brand). Just a question about oil weight -
5W-30 or 5W-40? I live in SoCal, mild climate. Any drawbacks of one versus the other?
Realize somethings about engine oil :
-- 0/5W30 oils shades into w20 viscosity within 1kMi
-- Most 0/5W40 oils are W30 stock oils thickened with polymers
-- What your engine moving parts require is film protection to minimize contacts... aka "scoring".
-- Replace your oil when it begins to dis-integrate, long before manufacturer recommended interval.
-- Use the best favorite oil within your comfort zone: either within MB specs or above it.
-- Blackened old thin oil is not what's best for Mercedes engine protection. Replace as soon as necessary or 3 to 5kMi.
---> With all due respects: final decisions are personal.
Last edited by CaliBenzDriver; Jan 5, 2025 at 12:26 AM.
Out of the 5w30 or 5w40 I would use the 5w40 if I were you. Looks like the 5w40 operates in higher and lower temps. Im sure your car will see +86 degrees in summer.
Im in New England so see hot summers into the 90's then winters in the single digits once in a great while. I use the Mobil1 0w40 because it is low cost locally and I used it in my previous vehicles so im just used to getting it.
Based on the chart in the back of the Operators manual. Your manual may be different.
@TimC300 Just a note: For the cars that fall under sheet 229.5, I also like 0/5W-40 oils. However, isn’t that chart for the lowest temperature that the car will see? For me, SE Texas, I always thought it meant use anything.
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