Skyactiv-D diesel carbon build-up and oil dilution on short journeys
- Typically appears
- 70,000+ miles
- What to inspect
- Check the oil level for rising level and test under load

A handsome saloon and estate with a strong reliability record, favoured by high-mileage private buyers.
Compiled & reviewed by the VehicleFaults Research Team · last reviewed August 2026
The most commonly reported faults on the 2013–2024 Mazda Mazda6 are Skyactiv-D diesel carbon build-up and oil dilution on short journeys, DPF blocking on town-used diesels and Notchy shifting, crunching, or resistance when selecting second or third gear on manual Skyactiv-MT models. 3 of the documented issues are rated high severity · inspect these first. Full inspection points, onset mileage and what to check are listed below.
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Guidance only · reflects reported patterns, not a specific car's condition.
Skyactiv-D diesel carbon build-up and oil dilution on short journeys
DPF blocking on town-used diesels
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Build the inspection planRear arch and sill corrosion on earlier cars
Bush and drop link wear at higher mileage
Infotainment screen delamination and 'ghost touch' erratic inputs without user interaction.
Power folding wing mirrors fail to retract or deploy, often accompanied by a continuous grinding noise.
Notchy shifting, crunching, or resistance when selecting second or third gear on manual Skyactiv-MT models.
Electronic Parking Brake (EPB) rear calipers seizing, causing dragging brakes and premature rear pad and disc wear.
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Build my inspection planOn motorway use, yes. On short journeys it suffers from oil dilution and carbon build-up.
An oil level above maximum. That is diesel in the sump and it needs addressing.
The Tourer estate sells faster and holds a premium in the UK market.
Yes. The 2.0-litre and 2.5-litre naturally aspirated Skyactiv-G petrols are exceptionally reliable and avoid the DPF and oil dilution issues of the diesels. They use a robust timing chain. Ensure the service history shows regular oil changes every 12,500 miles or 12 months to maintain variable valve timing health.
Mazda claims the automatic transmission is sealed for life, but UK specialists highly recommend a fluid and filter change every 60,000 miles. Old, degraded fluid causes harsh downshifts and torque converter shudder. Check the dipstick beneath the airbox for dark, burnt-smelling fluid during your appraisal.
Models equipped with i-ELOOP use a capacitor to store braking energy. If the specific Q85 or T110 EFB battery fails, replacing it is significantly more expensive than a standard unit. Ensure the dashboard shows no i-ELOOP warnings, as a failed DC-DC converter or capacitor costs over a thousand pounds.
Faults are compiled from documented recalls, technical bulletins, owner reports and mechanic sources, then reviewed for accuracy. This is guidance only · not a substitute for a professional inspection.
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