Question: is gtechniq c4 the same as c5?
Answer: If you didn't, C1, C4 and C5 are all the same product, branded differently, so just get the cheapest one and the quantity you need. This has been discussed a few times on detailing world and confirmed by gtechniq themselves. I very nearly bought some C4 even though I had half a bottle of C1 and half a bottle of C5.