The 204DTD Ingenium diesel generated more UK replacement enquiries in 2025 than any other Jaguar engine - 590 in total. The full ranking, the real cost data behind it, and what it means if you own one.
Across 3,010 real UK Jaguar engine enquiries in 2025, the 204DTD Ingenium diesel leads at 590 requests, followed by the AJ126 supercharged V6 at 560 - together accounting for over 38% of all Jaguar engine enquiries we handled last year.
Full methodology, the complete ranking, and what changed in this baseline year below.
What this data is, what it isn't, and how we built it.
Source: Internal CRM quote-request data from EnginesMarket.co.uk and EngineFinders.co.uk, combined. Full calendar year 2025. 24,650 unique quote requests across all brands we cover; 3,010 of these relate specifically to Jaguar engines.
What counts as an "enquiry": a unique customer quote request specifying a particular engine code or vehicle. Repeat requests from the same customer for the same engine are not double-counted.
What this data cannot tell you: our dataset reflects people who contacted us about a replacement engine - it is not a random sample of every Jaguar on UK roads. A higher enquiry count can mean an engine is more failure-prone, or simply that more of that engine exist in the parc, or that it's an older engine reaching typical replacement age. We do not claim failure rates against the total vehicle population; only enquiry share within our own dataset.
Refresh cycle: annually, each February, covering the prior full calendar year. Figures are locked at time of publication and are not silently revised - any correction is logged on our public corrections page rather than edited away.
All figures [EM-VERIFIED], full year 2025. Estimates marked ~ are derived from combined JLR data per our data usage rules.
Every Jaguar engine in our 2025 enquiry data, ranked, with real cost and vehicle-value context.
| Rank | Engine | 2025 Enquiries | Recon Supply & Fit | Typical Host Value | R-to-V Flag |
|---|---|---|---|---|---|
| 1 | 204DTD (Ingenium D) | 590 | £3,500–£5,800 | £10,000–£28,000 | ✅ Safe |
| 2 | AJ126 (3.0 V6 SC) | 560 | £4,500–£7,500 | £8,000–£30,000 | ✅ Safe |
| 3 | 204PT (Ingenium P) | 500 | £3,000–£5,000 | £10,000–£28,000 | ✅ Safe |
| 4 | AJ133 (5.0 V8 SC) | 330 | £5,500–£9,000 | £8,000–£35,000 | ✅ Safe |
| 5 | 276DT (2.7 TDV6) | [ESTIMATED] ~300 | £5,000–£7,500 | £4,000–£14,000 | ⚠️ Watch |
| 6 | AJ‑V8 (4.0/4.2) | [ESTIMATED] ~200 | £3,000–£5,500 | £4,000–£12,000 | ⚠️ Watch |
| 7 | AJ20D6 (3.0 straight-six diesel) | [ESTIMATED] ~120 | £4,500–£7,000 | £18,000–£45,000 | ✅ Safe |
| 8 | AJ20P6 (3.0 straight-six petrol) | [ESTIMATED] ~80 | £4,000–£6,500 | £25,000–£60,000 | ✅ Safe |
All enquiry figures [EM-VERIFIED] where shown as exact; estimates marked ~ derived from combined JLR data. Cost and value bands [EM-QUOTE / EM-INTERVIEW / THIRD-PARTY] per our data legend - full source detail on the Data Verification page.
Enquiry density isn't uniform across the UK, and the pattern broadly tracks Jaguar ownership density rather than any regional difference in driving conditions or climate. The South East and South West show the highest absolute enquiry volumes, consistent with higher regional ownership of XF and XJ models specifically. Scotland and the North of England show a higher proportion of X‑Type and S‑Type enquiries relative to newer models, consistent with older vehicle parc demographics in those regions. None of this changes the failure mechanisms described elsewhere on this site - a 204DTD timing chain fails the same way regardless of postcode - but it does mean specialist availability and typical wait times vary by region, which our registration lookup tool and specialist network account for when routing your enquiry. We will begin publishing a dedicated regional map as a standalone data page once the second full year of data is available, giving a year-on-year comparison rather than a single snapshot.
The three most-enquired engines - 204DTD, AJ126, and 204PT - are not necessarily the three "worst" engines Jaguar has built; they are simply the most common ones reaching typical replacement mileage across a large vehicle parc [PATTERN DATA]. What's more informative is the R-to-V column: almost every engine on this list clears our 60% safety threshold, meaning replacement is financially sound on the typical host vehicle. The two flagged ⚠️ Watch - 276DT and AJ‑V8 - are engines most often fitted to older, lower‑value hosts (X350, XJ, XK), where the calculation is closer and worth checking individually using our Repair vs Replace Calculator. For the full breakdown behind any single figure on this page, see Failure Rate by Engine, Average Mileage at Failure and Most Enquired Models.
It's also worth reading rank order alongside the underlying engine population rather than in isolation. The 204DTD and AJ126, for example, sit close together in enquiry volume despite the 204DTD being a four‑cylinder diesel fitted to a wider range of vehicles - which suggests, without our data being able to prove it definitively, that the 204DTD's timing chain issue may occur at a somewhat higher rate proportionally than the AJ126's cooling system failures, even though the AJ126 generates a similar absolute number of enquiries. This is the kind of nuance a bare ranking table can hide, and it's why we publish the full per-engine data pages rather than stopping at this summary.
Feel free to reference this data in press coverage, forum discussion, or your own research. Suggested attribution:
For press enquiries or the full underlying dataset, contact us via our About page. We're happy to provide additional context or breakdowns for journalists working on a related story.
The 204DTD (Ingenium diesel) leads with 590 enquiries in our 2025 data, followed by the AJ126 supercharged V6 at 560. This reflects both engines' popularity across the range, not a claim that either is unreliable by design.
Not on its own. Enquiry volume reflects how many vehicles are on the road with that engine as much as it reflects failure frequency. We pair enquiry data with our separate Known Failure Patterns research to distinguish popularity from reliability.
No, and we want to be upfront about that. Our dataset reflects people who contacted us about a replacement engine, which naturally over-represents engines that fail and under-represents ones that don't. Full methodology and limitations are set out in this report.
Annually, each February, covering the prior full calendar year. This is our first published edition and establishes the baseline every future report will be measured against.
3,010 Real EnquiriesThe full Jaguar-specific dataset behind every figure on this page.
Limitations DisclosedWe state plainly what this data can't tell you, not just what it can.
Annual PublicationRefreshed every February - this is our founding baseline year.
100% IndependentNo sponsors, no manufacturer influence.
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