TT AUTO'S Engineering
Practical reliability intelligence for BMW, Mercedes-Benz, Audi, and Volkswagen owners who want the mechanical truth before they buy, repair, or walk away.
Start here
Choose the fastest route to a smarter ownership decision
The homepage now acts like a control room: quick routes for research, model comparison, reliability concerns, and practical buying decisions.
Risk Checker
ToolScore a used German car before buying with service, scan, cold-start, leak, gearbox, and seller signals.
Search Library
FindFind topics by symptom, engine, gearbox, brand, platform, or fault pattern across the whole site.
Reliability Index
CoreCompare ownership risk by platform, engine, service sensitivity, and known failure patterns.
Buying Guides
BuyerUse structured inspection notes before committing to a German car purchase.
Direct Comparisons
CompareCompare engines and models buyers actually cross-shop, including B47 vs B48 and Golf vs A3.
Engineering Insights
Deep diveUnderstand the mechanism behind common symptoms instead of guessing from opinions.
Brand Hubs
BrandsMove quickly through BMW, Mercedes-Benz, Audi, and Volkswagen reliability topics.
Model Guides
ModelsStart with BMW 3 Series, Mercedes C-Class, Audi A4, and Volkswagen Golf buying pages.
Engine & Gearbox Library
DatabaseIdentify exact powertrains, known failure patterns, service priorities, and pre-purchase checks.
Compare
Direct used-buy comparisons
Short, practical matchups for the choices buyers actually make: engine versus engine, model versus model, and cross-brand diesel decisions.
Engine
BMW B47 vs B48
BMW diesel vs petrol used-buy comparison covering reliability, running cost, inspection risk, and ownership fit.
Engine
BMW N47 vs B47
BMW diesel generation comparison focused on timing-chain risk, emissions systems, maintenance evidence, and safer used buys.
Engine
Mercedes OM651 vs OM654
Mercedes diesel comparison for C-Class, E-Class, and GLC buyers deciding between older proven diesel and newer emissions complexity.
Cross-brand
Audi 2.0 TDI vs BMW B47
Cross-brand diesel comparison for buyers choosing between Audi/VW 2.0 TDI cars and BMW B47-powered models.
Model
Volkswagen Golf vs Audi A3
Compact VAG comparison covering value, premium feel, shared engines, DSG risk, and practical used-buy logic.
Model
BMW 3 Series vs Mercedes C-Class
Executive saloon comparison for buyers choosing between BMW dynamics and Mercedes comfort.
Featured technical insight
BMW B47 DPF and EGR Buying Signals
How to inspect a used BMW B47 diesel for DPF loading, EGR history, cooling faults, short-trip use, and weak diagnostic evidence.
Latest
Newest engineering insights
Recent technical explainers and reliability breakdowns from the insights library.
BMW B47 DPF and EGR Buying Signals
How to inspect a used BMW B47 diesel for DPF loading, EGR history, cooling faults, short-trip use, and weak diagnostic evidence.
Low Battery Voltage and Module Faults: Diagnose Power First
Weak batteries and voltage drops can create communication, sensor, gearbox, and convenience faults that imitate much larger problems.
BMW B48 Ownership Signals: What to Inspect Before Buying
A practical B48 inspection covering cooling stability, oil leaks, ignition quality, boost behavior, service history, and diagnostic evidence.
DPF Regeneration vs Blockage: Read the Evidence Before Replacing Parts
Understand soot load, ash load, differential pressure, exhaust temperature, driving pattern, and why forced regeneration is not a universal repair.
Reliability
Signal board
A quick visual summary of the type of scoring readers can explore in the full reliability index.
Diagnostic library
Technical topics now covered
The insights library now goes beyond model opinions into the systems that actually create ownership cost: gearboxes, emissions hardware, boost control, oil control, AWD service, and misfires.
Low Battery Voltage and Module Faults: Diagnose Power First
Weak batteries and voltage drops can create communication, sensor, gearbox, and convenience faults that imitate much larger problems.
DPF Regeneration vs Blockage: Read the Evidence Before Replacing Parts
Understand soot load, ash load, differential pressure, exhaust temperature, driving pattern, and why forced regeneration is not a universal repair.
Mercedes 9G-Tronic Buying Signals: Shift Quality, Fluid History, and Diagnosis
How to assess a used Mercedes 9G-Tronic through cold engagement, low-speed shifts, adaptation behavior, leaks, scan data, and service evidence.
AdBlue and NOx Faults: What Modern Diesel Buyers Should Know
A practical technical guide to SCR systems, NOx sensors, AdBlue pumps, countdown warnings, and why diesel emissions faults can become expensive.
Blog
Practical ownership notes
Shorter articles for buyers and owners who need useful judgment without a full technical teardown.
Audi 2.0 TDI vs BMW B47: Which Diesel Should You Trust?
A cross-brand diesel used-buy guide comparing Audi 2.0 TDI and BMW B47 engines through emissions systems, gearbox history, parts support, and inspection evidence.
Audi A4 vs BMW 3 Series: Which Used Saloon Makes More Sense?
A used-buyer comparison of Audi A4 and BMW 3 Series reliability, engines, gearboxes, driving feel, and inspection priorities.
BMW N47 vs B47: Which Used Diesel Is the Safer Buy?
A practical comparison of BMW N47 and B47 diesel engines for used buyers, focused on timing-chain risk, emissions systems, scan data, and service proof.
Brand hubs
Research by manufacturer
Each hub gathers common weaknesses, useful model notes, and the next pages to read before buying.
BMW
Engine families, cooling systems, turbo stress, and ownership-cost signals.
Mercedes-Benz
Engines, 7G/9G behavior, electronics, and long-term cost drivers.
Audi
TDI/TSI guidance, oil consumption, timing, cooling, and gearbox behavior.
Volkswagen
TSI/TDI and DSG deep dives, cooling weak points, sensors, and maintenance sensitivity.
Porsche
Performance-car inspection, PDK evidence, cooling, oil analysis, and chassis condition.
MINI
BMW-derived engines in a compact package: cooling, timing, oil, turbo, and electronics.
Škoda
VAG engineering with practical value: TSI/TDI, DSG, Haldex, cooling, and emissions.
SEAT / CUPRA
VAG platforms with a sportier edge: EA888, DSG, Haldex, cooling, and tuning history.
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