Truck and Tractor Unit Buying Guide: New and Used Engines, Axle Layouts and Emission Classes

What decides a truck purchase is the axle layout, emission class and body compatibility that suit the work. On a new vehicle, fuel consumption and warranty cover drive the case; on a used one, verified mileage and the overhaul history of the engine do.

Axle Layout and Application

Long-haul work is dominated by 4x2 and 6x2 tractor units, which carry more payload because they weigh less. Site, quarry and rough-ground work needs 6x4 drive. For tipper bodies, 8x4 has become the standard for both payload and axle load distribution. Refrigerated and curtain-side transport is usually well served by a 4x2 tractor, while heavy project cargo calls for 6x4 or 8x4.

Engine and Gearbox

The most common long-haul class is an 11-13 litre engine at 400-500 hp. Heavy tonnage and gradient-heavy routes call for 15-16 litre units at 500-650 hp. Automated manual transmissions (AMT) deliver 3-6 percent better fuel consumption than manuals and reduce driver fatigue. A retarder multiplies brake lining life several times over on mountain routes and is close to essential in long-haul service.

Emission Class and Operating Impact

Euro 5 vehicles use SCR (AdBlue). Euro 6 combines SCR, EGR and DPF, delivering lower fuel consumption but more expensive emission system faults. Euro 6 is increasingly mandatory for urban and European routes. When buying used, always verify that the DPF and SCR are original and active; deleted systems carry both legal risk and the risk of engine damage.

Class Comparison Table

Vehicle type	Typical engine	Axles	Fuel consumption	Overhaul threshold
Long-haul tractor unit	11-13 L / 420-480 hp	4x2, 6x2	27-33 L/100 km	800,000-1,200,000 km
Heavy haulage tractor	15-16 L / 540-650 hp	6x4	35-45 L/100 km	600,000-900,000 km
Tipper truck	11-13 L / 400-480 hp	8x4	40-55 L/100 km	400,000-600,000 km
Distribution truck	5-7 L / 210-280 hp	4x2	18-25 L/100 km	500,000-700,000 km
Concrete mixer	11-13 L / 400-450 hp	8x4	45-60 L/100 km	400,000-600,000 km

Used Truck Inspection Checklist

1. Verify real mileage from digital tachograph and service records, not just the dashboard reading.
2. Check for leaks at engine oil, coolant and turbo hoses, and for excessive exhaust smoke under load.
3. Read fault codes with an OBD tool; cleared but recurring codes are a serious warning.
4. Inspect the chassis for cracks, weld repairs and straightening marks; chassis damage is the most serious defect.
5. Measure brake lining thickness, check disc surfaces and run an air system leak-down test.
6. Check fifth wheel and king pin wear plus the suspension air bags.
7. Confirm SCR and DPF components are original and active.
8. Review roadworthiness certificate, insurance and any international operating permits.

Mercedes-Benz, MAN, Scania, Volvo Trucks, DAF, Iveco and Ford Trucks all have wide service coverage. On the trailer side, Tirsan, Krone and Schmitz Cargobull are the most commonly encountered brands.

Total Cost of Ownership

Fuel accounts for roughly two thirds of long-haul operating cost. A truck covering 120,000 km a year at 30 litres per 100 km burns around 36,000 litres annually, so even a 5 percent improvement saves 1,800 litres a year. Tyres are the second largest item: drive axle tyres last 120,000-180,000 km and trailer tyres can exceed 200,000 km. Add insurance, roadworthiness testing, tolls, driver cost and scheduled service, which on modern trucks falls every 60,000-120,000 km.

Operators who also need site loading equipment can review construction machinery, and for warehouse handling see forklifts and material handling.

Bodywork and Trailer Compatibility

A tractor unit or truck should be specified together with the body it will carry. On tippers, chassis length, wheelbase and PTO drive compatibility matter; on refrigerated transport, whether the reefer unit runs off the engine or an independent diesel; on tankers, ADR compliance and the number of compartments.

On the trailer side, fifth wheel height must match trailer kingpin height. A mismatch shifts the load forwards or backwards and can push axle loads past the legal limit. Overall height limits matter too; a low fifth wheel buys extra loading height for container and volume work.

When buying used, the body must appear on the registration document with a conversion project on file. Bodywork that is not registered creates problems at inspection and with insurance. Axle loads, kerb weight and gross combination weight must also suit your operation: a heavy tractor unit carries less payload on every trip, and that difference shows up directly in annual revenue.

New or Used?

For trucks, annual mileage decides. Fleets covering more than 100,000 km a year favour new vehicles for their lower fuel burn, warranty cover and strong residual values. For regional distribution and site work, used trucks use capital more efficiently.

Criterion	New machine	Used machine
Initial investment	High	Substantially lower
Lead time	8-30 weeks after order	Usually 1-3 weeks
Warranty and service	Manufacturer warranty, commissioning included	Limited or dealer warranty
Technology and efficiency	Euro 6 engine, AMT gearbox, fleet telematics	One or two generations behind
Spare parts	Secured for many years	Depends on model age
Depreciation	Steep loss in the first years	Much slower value loss
Finance and leasing	Suits leasing and incentives	Limited, needs appraisal

The clearest return on a new tractor unit is fuel: a current engine, aerodynamic cab and automated transmission together can save 8-12 percent against an older generation. Fleet telematics measures driver behaviour and makes maintenance predictive. Current emission and safety equipment can also be mandatory in urban low-emission zones and public tenders.

What to ask when buying new matters just as much as the used checklist:

• Lead time: the schedule from order confirmation to commissioning must be in writing.
• Warranty scope: duration, excluded parts and response time should be stated clearly.
• Service network: ask the distance to the nearest authorised service and its response time.
• Parts commitment: stock status and lead time for critical parts belong in the contract.
• Training and commissioning: confirm operator training and acceptance tests are included in the price.

Frequently Asked Questions

What mileage should I look for in a used tractor unit?

For long-haul units, 400,000-700,000 km is the best balance of price and remaining life. Above 900,000 km an engine, gearbox or differential overhaul is close, and that cost belongs in the negotiation.

Euro 5 or Euro 6?

For domestic short-haul and site work, Euro 5 remains economical. For European routes, urban low-emission zones and intensive long-haul, Euro 6 wins on both fuel consumption and regulatory compliance.

Do I need a retarder?

On mountain routes and heavy tonnage, a retarder extends brake lining life three to four times and markedly improves descent safety. On flat distribution routes the extra cost may not pay back.

How do I verify mileage?

Cross-check digital tachograph records, service history, inspection station records and the total fuel consumption counter in the vehicle ECU. If those four sources disagree, treat it as a serious red flag.

What should I check on a trailer?

Look for cracks in chassis and axle mounting welds, test the braking system and ABS-EBS module, and check axle bearings, air bags and floor condition. On refrigerated trailers, also check reefer unit hours and panel insulation.

At what mileage does a new tractor unit pay?

Above 100,000 km a year, fuel difference and warranty cover put new vehicles ahead in most calculations. Below 40,000 km a year, depreciation becomes the dominant cost item and a used vehicle is the more rational choice.

To compare new and used tractor units, trucks, tippers, mixers and trailers, browse the trucks and transport vehicles category.