Do you use synthetic oil?

[Jeece]

I use synthetic oil that meet the "official" requirement specs for my engine (according to VW). I also use OEM filters. These combined with my driving habits (90% country) allow me to change oil every 10k. (kilometers )

0W40 for Winter
5W40 for Summer

As for transmission, I hadn't had my car long enough to change it (previous owner did it before I bought the car 10 months ago). Plus I have a manual so it lasts longer.

[MazdaMatt]

When i started to take my daily driver to the race track, i started using nothing but pure syth. Previously Castrol Syntec, now Mobil 1. Not that I think one is better than the other or in any way noticibly different. The reason I switched is that running a car at 7000rpm is harsh on conventional and it is the concensus of the experts in my racing comunity (mechanics, dealer techs, race engine builders, race car builders, 10-, 20-, 30-, 40-, 50- and 60+-year racing experience) that synth shuold be used. My track car gets synth. I still put synth in my dd because it starts easier with it, especially in the cold. 5W-30 for both cars, year round. My truck will likely get conventional again when i change it next week.

[TomEV]

I use synthetic oil in the differential of my electric car - Hard to say if it makes much of a difference in efficiency (quantitative) because I have been changing other things at the same time.

The biggest change is qualitative - the gear sounds are more mellow/'cast iron' compared to the imperative 'brass' sound when using conventional dino gear oil.