Buying a C218 CLS500/550 M278
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Buying a C218 CLS500/550 M278
Considering Another C218 CLS550 (M278) – Looking for Insight on Engine Revisions and Preventive Maintenance
I'm currently considering purchasing another C218 CLS550 equipped with the M278 engine. I previously owned a 2014 model and had a completely trouble-free ownership experience from 64k miles to 90k miles. The car was stock up to 75k miles, and then tuned to approximately 600bhp and 740 ft-lb of torque. Despite the power increase, I experienced zero issues—no problems with the transmission, electronics, suspension, or drivetrain. I maintained regular oil changes and only used the highest available octane fuel (98 RON, equivalent to 93 in USA).
Once again I'm leaning toward the pre-facelift models (2011–2014), as I prefer the design language. Since my previous car was a 2014, I’m wondering if perhaps Mercedes made any notable changes to the M278 engine for that model year that could explain my trouble-free experience. For example, I know the final year of the M157 received forged pistons—did the M278 undergo any similar revisions during the pre-facelift production run?
Additionally, if anyone has suggestions on what I should specifically inspect beyond the usual compression and cylinder health checks, I’d appreciate the advice. I’m only considering examples with fewer than 80k miles, as my last car began having cooling system issues right after passing the 100k mark—a common failure point from what I’ve seen in the community.
Lastly, any recommended preventive maintenance steps to ensure reliability would be very helpful.
Looking forward to your input and experiences!
I'm currently considering purchasing another C218 CLS550 equipped with the M278 engine. I previously owned a 2014 model and had a completely trouble-free ownership experience from 64k miles to 90k miles. The car was stock up to 75k miles, and then tuned to approximately 600bhp and 740 ft-lb of torque. Despite the power increase, I experienced zero issues—no problems with the transmission, electronics, suspension, or drivetrain. I maintained regular oil changes and only used the highest available octane fuel (98 RON, equivalent to 93 in USA).
Once again I'm leaning toward the pre-facelift models (2011–2014), as I prefer the design language. Since my previous car was a 2014, I’m wondering if perhaps Mercedes made any notable changes to the M278 engine for that model year that could explain my trouble-free experience. For example, I know the final year of the M157 received forged pistons—did the M278 undergo any similar revisions during the pre-facelift production run?
Additionally, if anyone has suggestions on what I should specifically inspect beyond the usual compression and cylinder health checks, I’d appreciate the advice. I’m only considering examples with fewer than 80k miles, as my last car began having cooling system issues right after passing the 100k mark—a common failure point from what I’ve seen in the community.
Lastly, any recommended preventive maintenance steps to ensure reliability would be very helpful.
Looking forward to your input and experiences!
