Maurice is correct, gun wash has quite a lot of water in it, whereas non bloom thinners has next to none, hence the tin lasting years. I have some 10 years old, the tin is fine.
BTW never, ever use gun wash to save money or avoid a trip to buy more proper thinners. the water content gets trapped in the paint and even left several warm days and don't think primer being porous means it can't get trapped, it does.
Finish looks good till the first frost when the micro blisters appear.