Here in Canada we get -30 to -40 degrees F constantly in winter. Have never heard of antifreeze gelling here - even undiluted in jug stored at -30F. Have not seen enviro friendly type up here. One strange thing that happened on my son's VW diesel last winter - he was down a quart of oil in the motor (5w-30 QUAKER STATE) and stopped at a garage for a quart of same grade oil but another brand and put into the crankcase. The car was still cold (-35F that night) and he started home. The engine started clanking and losing power. He stopped and waited 20 minutes and started it up again. The engine clanked but seemed to have more power so he drove it home SLOWLY 20 miles. The next day he checked the dipstick and it was clean -no oil. He took out the oil pan drain plug and nothing came out. Pushing the car into the heated garage he took off the oil pan and it hit the floor with a bang. -It was full of oil BUT THE OIL HAD TURNED TO THICK JELLY. We kept the oil in a plastic pail for months to show others who did not believe us. The strange part is - when the oil in the pail was warmed to above freezing - it became fluid again!! After rebuilding the engine we now stick to one brand of oil for changes and top ups. TRUTH CAME BE STRANGER THAN FICTION!!