Hello, I own a 2015 Z06 equipped with 7 speed manual gearbox.

I must change the rear cooler on the right side of the car (don't know if it's the trans cooler or diff cooler) and during the replacing process some oil will leak. Which oil must I buy to top up?

After how many kilometres must change the oil? My car has 20.000 kilometres, just want to know if I must change all the oil or just top up..

Thanks in advance

 

The right side cooler is the differential cooler. With 20K Km you shouldn't be anywhere near needing to change the lubrication unless you had to repair or replace something. The differential lubricant should be listed in your Owner's Manual.

Rear Axle DEXRON® LS Gear Oil (GM Part No. 88862624, in Canada 88862625).

See Rear Axle on page 10-34 for information on checking the fluid.
Rear Axle

When to Check Lubricant
It is not necessary to regularly check rear axle fluid unless a leak is suspected or an unusual noise is heard. A fluid loss could indicate a problem. Have it inspected and repaired.

How to Check Lubricant
To get an accurate reading, the vehicle should be on a level surface. The fluid level should be at or within 13 mm (0.5 in) of the bottom of the fill plug hole threads. If it is at this level, no additional fluid is needed. If the fluid level is below 13 mm (0.5 in), add fluid until it is above this level.

What to Use
To add lubricant when the level is low or to completely refill after draining, see Recommended Fluids and Lubricants on page 11-12. Then fill to within 13 mm (0.5 in) of the bottom of the fill plug hole threads with the required lubricant.

Here is a link to the 2017 GM Owner's Manual (in US English) if you don't happen to have one. https://my.chevrolet.com/content/dam/gmownercenter/gmna/dynamic/manuals/2017/Chevrolet/Corvette/Owner's%20Manual.pdf. There are few differences between the 2015 and 2017 models and this one should be close enough for what you want to do.

Bill

 

It is not a bad idea to do regular replacement of the differential and transmission gear oil. Especially the diff, there is typically alot of initial break-in metal particles in the gear oil. I would change that within the first 5000 miles of use, then every 30,000 miles (and the transmission gear oil).

Also, some people have found that the differential is underfilled from the factory....so the level should be at least checked as soon as possible.