Hi guys,
Yesterday I was told by a mechanic that rotary engines do losse compression if the car sits in a garage for a long time and to prevent that you need to start the car regularly is it true,?

 

No, that's not how it works.
However, if you don't revv your engine every now and then, your seals and valves can gunk up.
I've left mine without running for 6+ months, and it's fired up just fine, no issues.

 

I'm under the impression that if its going to sit for a while its better to just prepare the engine for long term storage, remove the battery and just let it sit.

I bought a low mileage 13b-rew block that was sitting in a garage for over 10 years (yes I'm serious). The guy that I bought it from would just put in some oil every once in a while and give it a few cranks. The engine had normal compression.

 

I guess what information we're missing here is: how long is a long time?

OP search the winter storage threads to get an idea of what members do when storing for periods.