Two of Land Rover's most desirable diesel engines, head to head. The SDV6 is the lighter, more efficient V6; the SDV8 is the ultimate torque‑monster V8. Both are fitted to flagship models, but which one makes more sense in 2025? Here's the honest verdict.
The SDV8 is the better engine for ultimate luxury, refinement, and effortless torque, but the SDV6 is the more sensible choice for most buyers — cheaper to buy, cheaper to run, and still exceptionally capable. Our 2025 data shows the SDV6 (306DT) generated 980 enquiries versus the SDV8 (508PS) at 620 [EM-VERIFIED], reflecting the V6's broader appeal. The SDV8 delivers 4.4 litres of creamy V8 power, with 340 bhp and 700 Nm of torque, but carries a higher replacement cost and significantly higher running costs. The SDV6 offers 306 bhp and 700 Nm from a 3.0‑litre V6 – enough for almost any situation – with better fuel economy and lower purchase prices. For most buyers, the SDV6 is the smarter choice; for those who want the ultimate diesel experience, the SDV8 is peerless.
Full spec comparison, cost of ownership, and which engine to choose for your situation below.
| SDV6 (306DT) | SDV8 (508PS) | |
|---|---|---|
| Displacement | 3.0‑litre V6 | 4.4‑litre V8 |
| Power | 306 bhp | 340 bhp |
| Torque | 700 Nm | 700 Nm |
| 2025 UK Enquiries | 980 [EM-VERIFIED] | 620 [EM-VERIFIED] |
| Reconditioned S&F | £6,500–£9,500 | £8,000–£12,000 |
| R&R Labour | 15–20 hrs | 16–20 hrs |
| Defining Failure | Crankshaft bearing | Oil cooler / DPF (minor) |
| Best For | Daily driving, value, efficiency | Ultimate luxury, towing, refinement |
The SDV6 is the better choice for 95% of buyers. It delivers 700 Nm of torque – the same peak torque as the SDV8 – with significantly lower running costs, cheaper purchase prices, and a lower replacement cost. The SDV8 is a masterpiece – silky smooth, effortlessly powerful, and the ultimate statement – but it's also expensive to buy, run, and maintain. If you're buying a Range Rover or Sport and you genuinely need the extra refinement of a V8, or you simply want the pinnacle of diesel engineering, the SDV8 is worth every penny. For everyone else, the SDV6 offers 90% of the experience for 60% of the cost. Our data shows the SDV6 is far more popular, and that's for good reason [EM-VERIFIED].
The SDV6, also known as the 306DT, is a 3.0‑litre V6 diesel producing 306 bhp and 700 Nm of torque. It's fitted to a wide range of Land Rover models, including the Discovery 4, Range Rover L405, Range Rover Sport L494, and Velar. It offers strong performance, good fuel economy (around 30–33 mpg real‑world), and a lower purchase price than the V8. Its main documented weakness is crankshaft bearing failure, typically between 80,000 and 140,000 miles [PATTERN DATA]. A full reconditioned engine costs £6,500–£9,500 [EM-QUOTE]. Despite this risk, the SDV6 is a proven, reliable engine when maintained with regular oil changes. Full specs and reliability data are on the 306DT Knowledge Centre, and the 306DT Crankshaft Bearing Failure page covers the risk in detail. For most buyers, the SDV6 is the sensible, capable, and enjoyable choice.
The SDV8, also known as the 508PS or 4.4 SDV8, is a 4.4‑litre V8 diesel producing 340 bhp and 700 Nm of torque. It's fitted to the Range Rover L405 and Range Rover Sport L494, offering effortless, wafting refinement and a genuinely luxurious driving experience. It's smoother, quieter, and more refined than the V6, and its 700 Nm of torque is delivered with a creamy urgency that makes the SDV6 feel busy by comparison. The SDV8 is generally robust, with no catastrophic design flaw [PATTERN DATA] – its main issues are minor: oil cooler leaks, DPF regeneration‑related oil dilution, and occasional alternator failures. Replacement costs are higher at £8,000–£12,000 [EM-QUOTE], and running costs are significantly higher – around 25–28 mpg. Full specs are on the 508PS Knowledge Centre. The SDV8 is for buyers who prioritise refinement above all else.
The SDV6 is significantly cheaper to own over five years. The purchase price difference is the biggest factor – a used SDV6‑powered Range Rover typically costs £3,000–£6,000 less than an equivalent SDV8. Running costs are also lower: the SDV6's 30–33 mpg compares to 25–28 mpg for the SDV8, saving around £500–£800 per year in fuel. Insurance is cheaper, VED is lower, and servicing costs are marginally reduced. The SDV6's replacement cost is also lower (£6,500–£9,500 vs £8,000–£12,000). Even factoring in the SDV6's crankshaft bearing risk, the probability‑weighted cost of ownership strongly favours the V6. The SDV8's only real advantage is refinement – and for many buyers, that's worth the premium. For a detailed breakdown, our ownership cost calculator can model your specific mileage and usage.
Choose the SDV6. It offers 700 Nm of torque, strong performance, and much lower running costs. The SDV6 is more than enough for daily driving and towing, and it's cheaper to buy and maintain.
Choose the SDV8. Its silky‑smooth V8 character, effortless power delivery, and quietness make it the ultimate diesel experience. If you can afford it, you'll never regret the V8.
Both have 700 Nm, so towing capacity is identical. The SDV8 is more refined under load, but the SDV6 is perfectly capable. The SDV6's better fuel economy may be an advantage on long trips.
Both can reach high mileages with care. The SDV6's lower running costs make it a better long‑term proposition, but the SDV8's rarity may support resale values. For a decade of ownership, the SDV6's fuel savings alone could pay for a significant portion of a replacement engine.
Whichever you choose, the repair vs replace framework and the ownership cost calculator can help you decide whether to fix or move on when the bills arrive.
The SDV8 is generally more reliable – it has no catastrophic design flaw and its main issues (oil cooler, DPF) are manageable. The SDV6 has a well‑documented crankshaft bearing failure risk. However, the SDV6 is more common, and its failure, while serious, is well‑understood and can be mitigated with frequent oil changes.
The SDV6 is cheaper – reconditioned supply and fit is £6,500–£9,500 versus £8,000–£12,000 for the SDV8, mainly due to lower parts cost and slightly less labour.
For buyers who value refinement and luxury above all else, yes. The SDV8 is smoother, quieter, and more effortless than the SDV6. If you can afford the higher purchase price and running costs, it's a genuinely special engine.
Both have 700 Nm of torque, so towing capacity is identical. The SDV8 is more refined under load, but the SDV6 is perfectly capable. The SDV6's better fuel economy may be an advantage for long‑distance towing.
1,600 Combined EnquiriesBoth engines analysed from real 2025 UK data.
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