Side-by-side comparisons of Mercedes-Benz engines, models and ownership economics — all built from real UK enquiry data and specialist insight.
Compare Mercedes-Benz engines, models and ownership costs directly. This page indexes every head-to-head comparison we've built — from engine-family clashes like OM651 vs OM642 to model showdowns like C-Class vs E-Class. Each comparison uses real 2025 UK data [EM-VERIFIED] to give you a clear verdict, not a marketing pitch.
Use the index below to find the comparison that matches your decision. If you're still deciding which Mercedes to own, start with the diesel vs petrol running costs guide or use our ownership cost calculator for a personalised estimate.
Which Mercedes model suits you best? These head-to-heads compare running costs, engine options and real-world ownership outcomes.
Executive saloon or larger estate? Running costs, engine options and which holds value better.
The mid-size executive vs the flagship — when the extra cost of the S-Class actually makes sense.
The two most popular Mercedes SUVs in the UK, compared on cost, space and engine choices.
Older boxy GLK vs the newer GLC — is the upgrade worth the premium? Real data answer.
Large SUV vs extra-large 7-seat — engine replacement costs, running costs and which fits.
Hatchback vs four-door coupe — same platform, different ownership costs and image.
Previous-generation C-Class against the current — which is the smarter buy in 2025?
The classic W211 against the more modern W212 — reliability, rust and replacement economics.
Latest-generation E-Class comparison — spec differences, engine availability and cost.
The outgoing S-Class vs the new generation — what changed and is it worth upgrading.
Mercedes van comparison — engine durability, replacement costs and which fits your business.
The most-asked engine comparisons in our data. OM651 vs OM642, M272 vs M276, and more — all backed by real 2025 UK enquiry volumes.
Four-cylinder vs V6 diesel. OM651: 1,250 enquiries, OM642: 880 enquiries in 2025 [EM-VERIFIED]. Which is better value?
The newer OM654 (520 enquiries) against the established OM651 (1,250) — reliability, cost and real-world feedback.
Earlier 4-cylinder diesel vs the later OM651. Known injector seal and chain issues compared.
The classic M272 V6 petrol (with balance-shaft chain risk) vs the newer M276 V6 with direct injection.
Four-cylinder petrol comparison — timing chain tensioner risks, turbo response and replacement costs.
V6 vs V8 petrol. M276 petrol (390 enquiries) against the twin-turbo M278 — cost and ownership experience.
AMG V8 petrol comparison. M157 (AMG, 5.5L) vs M178 (AMG GT, 4.0L) — running costs and replacement.
Not just engine vs engine — these comparisons answer the bigger question: which approach fits your budget, driving style and ownership horizon?
The definitive guide to Mercedes diesel vs petrol running costs in 2025 — fuel, tax, servicing and the DPF factor.
AMG V8 showdown — smaller and sharper vs larger and more refined. Real cost of ownership for both.
AMG V8s compared on real-world running costs, replacement economics and ownership patterns.
The four-cylinder OM651 and the V6 OM642 are the two most-enquired Mercedes diesels in our data — 1,250 vs 880 enquiries in 2025 [EM-VERIFIED]. The OM651 is cheaper to replace (£2,800–£4,800 recon supply) and fitted across more models, but the OM642 offers more refinement and torque in larger vehicles like the E-Class, ML and GLE. The OM651's chain tensioner is a known risk; the OM642's oil cooler seal and swirl flap issues are well-documented. Both are safe to replace against typical host values, but the OM651 wins on cost-per-mile for most buyers.
All comparisons use the same repair vs replace framework and are linked to our Engine Failure Index.
The OM651 is generally considered more reliable in terms of major failure frequency, though its timing chain tensioner is a known risk. The OM642 is more complex (V6) and has documented oil cooler and swirl flap issues, but many examples exceed 150,000 miles with proper maintenance. The OM654 is the most modern and generally the most robust, but fewer examples have reached high mileage yet.
In most cases, yes — the OM651 is one of the most common and well-supported Mercedes diesels in the UK. A reconditioned OM651 costs around £2,800–£4,800 supply-only [EM-QUOTE], and most host vehicles (C-Class, E-Class, GLC) are worth well above that. Always apply the 70% threshold: if the fitted cost exceeds 70% of the vehicle's current market value, evaluate scrap options first.
For diesel, the OM654 (2016+) is the most refined and reliable modern unit. For petrol, the M276 V6 and M274 four-cylinder are well-regarded, with the M276 being more robust than the earlier M272. The OM642 V6 diesel is a strong choice if regularly maintained and driven on longer runs.
Engine replacement costs vary significantly: the OM651 (C-Class/E-Class/GLC) is cheapest at £2,800–£4,800 supply-only. The OM642 V6 diesel runs £3,200–£5,500. The M276 V6 petrol is similar at £3,800–£6,500. AMG engines (M157, M178) are substantially more expensive, often exceeding £8,000 supply-only. Use the ownership cost calculator for a personalised estimate on your specific model.
Yes — see M157 vs M178 for AMG V8 petrol comparisons, and C63 vs E63 for full AMG model comparisons.
23 Comparisons
Built from real 2025 UK enquiry data [EM-VERIFIED]
15+ Vetted Specialists
Experienced with all Mercedes engine families
70% Threshold Applied
Clear repair-vs-replace guidance for every engine
100% Independent
No sponsors, no manufacturer influence
Use our ownership cost calculator to compare running costs and replacement economics for your shortlist.
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