TD5 Stage 2 Tuned Oil Viscosity Question?

Any reason to use a specific viscosity just because you have a stage 2 map over standard tune?

Yes, there are valid reasons to consider a specific oil viscosity for a stage 2 tuned Land Rover Defender 2.5L TD5 over the standard engine tune. A stage 2 tune increases power and torque, putting additional stress on the engine, which may necessitate an oil with different properties to ensure proper protection and performance.

Here’s why viscosity matters for a tuned engine:

1. Increased Stress on Engine Components
A stage 2 tune generally results in higher combustion pressures and temperatures. This can increase wear on critical components such as pistons, rings, bearings, and camshafts. A slightly thicker oil (higher viscosity) at operating temperature may provide a more robust oil film to handle the increased loads.
2. Higher Operating Temperatures
Tuned engines may run hotter due to increased fuel and air flow. An oil with higher thermal stability and viscosity can better maintain its protective properties at elevated temperatures.
3. Turbocharger Protection
The TD5 engine is turbocharged, and with a stage 2 tune, the turbo may experience higher boost pressures and temperatures. A higher viscosity oil or one with superior high-temperature stability (e.g., synthetic oils) can better protect the turbo’s bearings.
4. Manufacturer Recommendations
Land Rover typically recommends a specific oil grade for standard TD5 engines, such as 5W-30 or 10W-40, depending on climate. For tuned engines, upgrading to a fully synthetic oil with higher shear resistance (e.g., 5W-40 or 10W-50) is often advisable to handle the increased demands.
5. Oil Additive Requirements
Performance oils designed for tuned engines often have enhanced additive packages, including anti-wear agents, detergents, and dispersants, which are crucial for high-performance applications.
Recommendations:
Oil Viscosity: Consider using 5W-40 or 10W-50 fully synthetic oil for a stage 2 TD5.
Oil Brand: Use a high-quality brand such as Mobil 1, Castrol Edge, or Liqui Moly with a proven track record for performance engines.
Service Intervals: With a tuned engine, consider reducing oil change intervals to account for the increased stresses and potential oil degradation.

Appreciate you taking the time @Tim4x4
I run Castrol E fully syn 5w30, A5B5 servicing soon so was going to move to 5w40, my service intervals are on average 4K.

That sounds like you are well on top of your lube needs.
Good choice