Is it normal for the oil to have a white substance on the dipstick in the cold weather
Not really. That white substance may be water. If it is just a little then it may be condensation but a lot could be a leaking head gasket. I would change the oil and filter and keep an eye on it. If you only drive short distances then there can be a lot of condensation. Every now and then you need to drive the car until it is fully warmed up.
I agree with above
ive driven mine for 30,000 mls and hav always had it on the dip stick but yes keep topping up every 1000 mls and reg oil changes every 3000mls and it should be ok
Looking for a Used RX-8 in your area?
CarGurus has 302 nationwide RX-8 listings starting at $1,997.
Search Mazda RX-8 Questions
Mazda RX-8 Experts
Related Models For Sale