Loc: A Warm place to live in
A friend changed his differential gear oil in his Toyota HiLux. It called for GL-5 but he found himself in a pinch with not enough GL-5 to fill up with. So he put in 0.8 liter of GL-4 he had lying around to make up the difference. This was about 20% of the total gear oil volume he put in. Is he good? He uses the pickup only for mild to moderate load use.